Author name code: lagg
ADS astronomy entries on 2022-09-14
author:"Lagg, Andreas" 
------------------------------------------------------------------------  

Title: Polarimetric calibration of the Sunrise UV Spectropolarimeter
    and Imager
Authors: Iglesias, F. A.; Feller, A.; Gandorfer, A.; Lagg, A.;
   Riethmüller, T. L.; Solanki, S. K.; Katsukawa, Y.; Kubo, M.;
   Zucarelli, G.; Sanchez, M.; Sunrise Team
Bibcode: 2022BAAA...63..305I
Altcode:
  Sunrise is an optical observatory mounted in a stratospheric balloon,
  developed to study magnetic fields in the solar atmosphere with very
  high resolution. In its third flight, Sunrise carry the Sunrise UV
  Spectropolarimeter and Imager (SUSI), that operates in the 313-430 nm
  range, covering thousands of spectral lines not accessible from the
  ground and thus largely unexplored. SUSI does not include a polarimetric
  calibration unit on board. We report about the development status of
  SUSI and the preliminary results of its calibration.

Title: Magnetized supersonic downflows in the chromosphere. A
    statistical study using the He I 10 830 Å lines
Authors: Sowmya, K.; Lagg, A.; Solanki, S. K.; Castellanos Durán,
   J. S.
Bibcode: 2022A&A...661A.122S
Altcode: 2022arXiv220211679S
  The chromosphere above active regions (ARs) on the Sun hosts
  magnetized supersonic downflows. Studies of these supersonic downflows
  help to decipher the magnetic fine structure and dynamics of the
  chromosphere. We perform a statistical analysis of the magnetized
  supersonic downflows in a number of ARs at different evolutionary stages
  and survey their characteristics. We analyze spectro-polarimetric scans
  of parts of 13 ARs obtained in the infrared He I 10 830 Å triplet
  formed in the upper chromosphere recorded with the GREGOR Infrared
  Spectrograph mounted at the GREGOR solar telescope. We retrieve
  the line-of-sight velocities and the magnetic field vector using
  the HELIX<SUP>+</SUP> inversion code that assumes Milne-Eddington
  atmospheres. We find magnetized supersonic downflows in all the ARs,
  with larger area coverage by such flows in ARs observed during their
  emerging phase. The fact that supersonic downflows were detected
  in all scans, albeit only covering a small fraction, 0.2-6.4%, of
  the observed field-of-view, suggests that they are a comparatively
  common phenomenon in the upper chromospheres of ARs. The supersonic
  downflows are found to be associated with many AR features, such as
  pores, sunspot umbrae, sunspot penumbrae, light bridges, plages, He
  I loops as part of arch filament systems characteristic of emerging
  fields, and filaments. Although several mechanisms are identified to be
  causing the supersonic downflows, by far the most common one appears to
  be the draining of plasma along the legs of rising magnetic loops. The
  loops mainly drain into forming pores. The line-of-sight velocities of
  the supersonic downflows reach values of up to 49 km s<SUP>−1</SUP>,
  and the velocity distribution shows multiple populations. Almost 92% of
  these supersonic downflows coexist with a subsonic flow component. The
  weaker, more horizontal fields associated with the supersonic component
  suggests that it is formed above the subsonic component.

Title: The magnetic drivers of campfires seen by the Polarimetric
    and Helioseismic Imager (PHI) on Solar Orbiter
Authors: Kahil, F.; Hirzberger, J.; Solanki, S. K.; Chitta, L. P.;
   Peter, H.; Auchère, F.; Sinjan, J.; Orozco Suárez, D.; Albert,
   K.; Albelo Jorge, N.; Appourchaux, T.; Alvarez-Herrero, A.; Blanco
   Rodríguez, J.; Gandorfer, A.; Germerott, D.; Guerrero, L.; Gutiérrez
   Márquez, P.; Kolleck, M.; del Toro Iniesta, J. C.; Volkmer, R.;
   Woch, J.; Fiethe, B.; Gómez Cama, J. M.; Pérez-Grande, I.; Sanchis
   Kilders, E.; Balaguer Jiménez, M.; Bellot Rubio, L. R.; Calchetti,
   D.; Carmona, M.; Deutsch, W.; Fernández-Rico, G.; Fernández-Medina,
   A.; García Parejo, P.; Gasent-Blesa, J. L.; Gizon, L.; Grauf, B.;
   Heerlein, K.; Lagg, A.; Lange, T.; López Jiménez, A.; Maue, T.;
   Meller, R.; Michalik, H.; Moreno Vacas, A.; Müller, R.; Nakai,
   E.; Schmidt, W.; Schou, J.; Schühle, U.; Staub, J.; Strecker, H.;
   Torralbo, I.; Valori, G.; Aznar Cuadrado, R.; Teriaca, L.; Berghmans,
   D.; Verbeeck, C.; Kraaikamp, E.; Gissot, S.
Bibcode: 2022A&A...660A.143K
Altcode: 2022arXiv220213859K
  Context. The Extreme Ultraviolet Imager (EUI) on board the Solar Orbiter
  (SO) spacecraft observed small extreme ultraviolet (EUV) bursts,
  termed campfires, that have been proposed to be brightenings near the
  apexes of low-lying loops in the quiet-Sun atmosphere. The underlying
  magnetic processes driving these campfires are not understood. <BR
  /> Aims: During the cruise phase of SO and at a distance of 0.523
  AU from the Sun, the Polarimetric and Helioseismic Imager on Solar
  Orbiter (SO/PHI) observed a quiet-Sun region jointly with SO/EUI,
  offering the possibility to investigate the surface magnetic field
  dynamics underlying campfires at a spatial resolution of about 380
  km. <BR /> Methods: We used co-spatial and co-temporal data of the
  quiet-Sun network at disc centre acquired with the High Resolution
  Imager of SO/EUI at 17.4 nm (HRI<SUB>EUV</SUB>, cadence 2 s) and the
  High Resolution Telescope of SO/PHI at 617.3 nm (HRT, cadence 2.5
  min). Campfires that are within the SO/PHI−SO/EUI common field
  of view were isolated and categorised according to the underlying
  magnetic activity. <BR /> Results: In 71% of the 38 isolated events,
  campfires are confined between bipolar magnetic features, which seem to
  exhibit signatures of magnetic flux cancellation. The flux cancellation
  occurs either between the two main footpoints, or between one of the
  footpoints of the loop housing the campfire and a nearby opposite
  polarity patch. In one particularly clear-cut case, we detected the
  emergence of a small-scale magnetic loop in the internetwork followed
  soon afterwards by a campfire brightening adjacent to the location
  of the linear polarisation signal in the photosphere, that is to
  say near where the apex of the emerging loop lays. The rest of the
  events were observed over small scattered magnetic features, which
  could not be identified as magnetic footpoints of the campfire hosting
  loops. <BR /> Conclusions: The majority of campfires could be driven
  by magnetic reconnection triggered at the footpoints, similar to the
  physical processes occurring in the burst-like EUV events discussed
  in the literature. About a quarter of all analysed campfires, however,
  are not associated to such magnetic activity in the photosphere, which
  implies that other heating mechanisms are energising these small-scale
  EUV brightenings.

Title: Similarities of magnetoconvection in the umbra and in the
    penumbra of sunspots
Authors: Löptien, B.; Lagg, A.; van Noort, M.; Solanki, S. K.
Bibcode: 2021A&A...655A..61L
Altcode: 2021arXiv211001352L
  Context. It is unclear why there is a rather sharp boundary in
  sunspots between the umbra and the penumbra. Both regions exhibit
  magnetoconvection, which manifests in penumbral filaments in the
  penumbra and in umbral dots in the umbra. <BR /> Aims: Here we compare
  the physical properties of umbral dots and penumbral filaments. Our
  goal is to understand how the properties of these convective features
  change across the boundary between the umbra and the penumbra
  and how this is related to the rapid increase in brightness at the
  umbra-penumbra boundary. <BR /> Methods: We derived ensemble averages
  of the physical properties of different types of convective features
  based on observations of two sunspots with Hinode. <BR /> Results:
  There are strong similarities between the convective features in the
  outer parts of the umbra and the ones in the penumbra, with most
  physical parameters being smooth and continuous functions of the
  length of the features. <BR /> Conclusions: Our results indicate
  that the transition in brightness from the umbra to the penumbra
  is solely caused by an increased effectiveness of magnetoconvection
  within individual convective cells. There is no significant difference
  in the number density of convective elements between the outer umbra
  and the inner penumbra. Penumbral filaments exhibit a larger area and
  a higher brightness compared to umbral dots. It is still unclear how
  exactly the underlying magnetic field causes the increase in the size
  and brightness of convective features in the penumbra.

Title: Inferring magnetic helicity spectrum in spherical domains:
    Method and example applications
Authors: Prabhu, A. P.; Singh, N. K.; Käpylä, M. J.; Lagg, A.
Bibcode: 2021A&A...654A...3P
Altcode: 2021arXiv210407588P
  Context. Obtaining observational constraints on the role of turbulent
  effects for the solar dynamo is a difficult, yet crucial, task. Without
  such knowledge, the full picture of the operation mechanism of the
  solar dynamo cannot be formed. <BR /> Aims: The magnetic helicity
  spectrum provides important information about the α effect. Here
  we demonstrate a formalism in spherical geometry to infer magnetic
  helicity spectra directly from observations of the magnetic field,
  taking into account the sign change of magnetic helicity across the
  Sun's equator. <BR /> Methods: Using an angular correlation function of
  the magnetic field, we develop a method to infer spectra for magnetic
  energy and helicity. The retrieval of the latter relies on a fundamental
  definition of helicity in terms of linkage of magnetic flux. We apply
  the two-scale approach, previously used in Cartesian geometry, to
  spherical geometry for systems where a sign reversal of helicity is
  expected across the equator on both small and large scales. <BR />
  Results: We test the method by applying it to an analytical model
  of a fully helical field, and to magneto-hydrodynamic simulations
  of a turbulent dynamo. The helicity spectra computed from the vector
  potential available in the models are in excellent agreement with the
  spectra computed solely from the magnetic field using our method. In
  a next test, we use our method to obtain the helicity spectrum from a
  synoptic magnetic field map corresponding to a Carrington rotation. We
  observe clear signs of a bihelical spectrum of magnetic helicity,
  which is in complete accordance to the previously reported spectra
  in literature from the same map. <BR /> Conclusions: Our formalism
  makes it possible to infer magnetic helicity in spherical geometry,
  without the necessity of computing the magnetic vector potential. It
  has many applications in solar and stellar observations, but can also
  be used to analyse global magnetoconvection models of stars and to
  compare them with observations.

Title: How rare are counter Evershed flows?
Authors: Castellanos Durán, J. S.; Lagg, A.; Solanki, S. K.
Bibcode: 2021A&A...651L...1C
Altcode: 2021arXiv210605592S
  One of the main characteristics of sunspot penumbrae is the radially
  outward-directed Evershed flow. Only recently have penumbral regions
  been reported with similar characteristics to normal penumbral
  filaments but with an opposite direction of the flow. Such flows
  directed toward the umbra are known as counter Evershed flows
  (CEFs). We aim to determine the occurrence frequency of CEFs in
  active regions (ARs) and to characterize their lifetime and the
  prevailing conditions in the ARs. We analyzed the continuum images,
  Dopplergrams, and magnetograms recorded by SDO/HMI of 97 ARs that
  appeared from 2011 to 2017. We followed the ARs for 9.6 ± 1.4 days
  on average. We found 384 CEFs in total, with a median value of six
  CEFs per AR. Counter Evershed flows are a rather common feature,
  occurring in 83.5% of all ARs regardless of the magnetic complexity
  of the AR. However, CEFs were only observed, on average, during 5.9%
  of the mean total duration of all the observations analyzed here. The
  lifetime of CEFs follows a log-normal distribution with a median value
  of 10.6<SUB>−6.0</SUB><SUP>+12.4</SUP> h. In addition, we report two
  populations of CEFs, those that are associated with light bridges and
  those that are not. We explain that the rarity of reports of CEFs in
  the literature is a result of highly incomplete coverage of ARs with
  spectropolarimetric data. By using the continuous observations now
  routinely available from space, we are able to overcome this limitation.

Title: The magnetic fine structure of the Sun's polar region as
    revealed by Sunrise
Authors: Prabhu, A.; Lagg, A.; Hirzberger, J.; Solanki, S. K.
Bibcode: 2020A&A...644A..86P
Altcode:
  Context. Polar magnetic fields play a key role in the solar magnetic
  cycle and they are the source of a significant portion of the
  interplanetary magnetic field. However, observations of the poles
  are challenging and hence our understanding of the polar magnetic
  environment is incomplete. <BR /> Aims: We deduce properties of
  small-scale magnetic features in the polar region using high-resolution
  data and specifically aim to determine the flux per patch above which
  one magnetic polarity starts to dominate over the other. <BR /> Methods:
  We study the high spatial resolution, seeing-free observations of the
  north solar polar region, obtained with the IMaX instrument on-board
  the balloon-borne SUNRISE observatory during June 2009, at the solar
  activity minimum. We performed inversions of the full Stokes vector
  recorded by IMaX to retrieve atmospheric parameters of the Sun's
  polar region, mainly the temperature stratification and the magnetic
  field vector. <BR /> Results: We infer kilo-Gauss (kG) magnetic fields
  in patches harbouring polar faculae, without resorting to a magnetic
  filling factor. Within these patches we find the maxima of the magnetic
  field to be near the dark narrow lanes, which are shifted towards the
  disc centre side in comparison to the maxima in continuum intensity. In
  contrast, we did not find any fields parallel to the solar surface
  with kG strengths. In addition to the kG patches, we found the polar
  region to be covered in patches of both polarities, which have a range
  of sizes. We find the field strength of these patches to increase with
  increasing size and flux, with the smaller patches showing a significant
  dispersion in field strength. The dominating polarity of the north
  pole during this phase of the solar cycle is found to be maintained
  by the larger patches with fluxes above 2.3 × 10<SUP>17</SUP> Mx.

Title: The SUNRISE UV Spectropolarimeter and imager for SUNRISE III
Authors: Feller, Alex; Gandorfer, Achim; Iglesias, Francisco A.;
   Lagg, Andreas; Riethmüller, Tino L.; Solanki, Sami K.; Katsukawa,
   Yukio; Kubo, Masahito
Bibcode: 2020SPIE11447E..AKF
Altcode:
  Sunrise is a balloon-borne solar observatory dedicated to the
  investigation of key processes of the magnetic field and the plasma
  flows in the lower solar atmosphere. The observatory operates in
  the stratosphere at an altitude of around 37 km in order to avoid
  image degradation due to turbulence in the Earth's atmosphere and to
  access the UV range. The third science flight of Sunrise will carry new
  instrumentation which samples the solar spectrum over a broad wavelength
  domain from the UV to the near IR and covers an extended height range in
  the solar atmosphere. A key feature of the Sunrise UV Spectropolarimeter
  and Imager (SUSI) operating between 309 nm and 417 nm, is its capability
  to simultaneously record a large number of spectral lines. By combining
  the spectral and polarization information of many individual lines
  with different formation heights and sensitivities, the accuracy and
  the height resolution of the inferred atmospheric parameters can be
  significantly increased. The spectral bands of SUSI are selected one
  at a time by rotating a diffraction grating with respect to a fixed
  polarimetry unit. The spatial and spectral field of view on the 2k x
  2k cameras is 59" and 2.0 - 2.3 nm, respectively. A further innovation
  is the numerical restoration of the spectrograph scans by means of
  synchronized 2D context imaging, a technique that has recently produced
  impressive results at ground-based solar observatories.

Title: Sunrise Chromospheric Infrared SpectroPolarimeter (SCIP)
for sunrise III: system design and capability
Authors: Katsukawa, Y.; del Toro Iniesta, J. C.; Solanki, S. K.;
   Kubo, M.; Hara, H.; Shimizu, T.; Oba, T.; Kawabata, Y.; Tsuzuki,
   T.; Uraguchi, F.; Nodomi, Y.; Shinoda, K.; Tamura, T.; Suematsu,
   Y.; Ishikawa, R.; Kano, R.; Matsumoto, T.; Ichimoto, K.; Nagata, S.;
   Quintero Noda, C.; Anan, T.; Orozco Suárez, D.; Balaguer Jiménez,
   M.; López Jiménez, A. C.; Cobos Carrascosa, J. P.; Feller, A.;
   Riethmueller, T.; Gandorfer, A.; Lagg, A.
Bibcode: 2020SPIE11447E..0YK
Altcode:
  The Sunrise balloon-borne solar observatory carries a 1 m aperture
  optical telescope and provides us a unique platform to conduct
  continuous seeing-free observations at UV-visible-IR wavelengths from
  an altitude of higher than 35 km. For the next flight planned for
  2022, the post-focus instrumentation is upgraded with new spectro-
  polarimeters for the near UV (SUSI) and the near-IR (SCIP), whereas
  the imaging spectro-polarimeter Tunable Magnetograph (TuMag) is capable
  of observing multiple spectral lines within the visible wavelength. A
  new spectro-polarimeter called the Sunrise Chromospheric Infrared
  spectroPolarimeter (SCIP) is under development for observing near-IR
  wavelength ranges of around 770 nm and 850 nm. These wavelength ranges
  contain many spectral lines sensitive to solar magnetic fields and
  SCIP will be able to obtain magnetic and velocity structures in the
  solar atmosphere with a sufficient height resolution by combining
  spectro-polarimetric data of these lines. Polarimetric measurements are
  conducted using a rotating waveplate as a modulator and polarizing beam
  splitters in front of the cameras. The spatial and spectral resolutions
  are 0.2" and 2 105, respectively, and a polarimetric sensitivity of
  0.03 % (1σ) is achieved within a 10 s integration time. To detect
  minute polarization signals with good precision, we carefully designed
  the opto-mechanical system, polarization optics and modulation, and
  onboard data processing.

Title: Coordination within the remote sensing payload on the Solar
    Orbiter mission
Authors: Auchère, F.; Andretta, V.; Antonucci, E.; Bach, N.;
   Battaglia, M.; Bemporad, A.; Berghmans, D.; Buchlin, E.; Caminade,
   S.; Carlsson, M.; Carlyle, J.; Cerullo, J. J.; Chamberlin, P. C.;
   Colaninno, R. C.; Davila, J. M.; De Groof, A.; Etesi, L.; Fahmy,
   S.; Fineschi, S.; Fludra, A.; Gilbert, H. R.; Giunta, A.; Grundy,
   T.; Haberreiter, M.; Harra, L. K.; Hassler, D. M.; Hirzberger, J.;
   Howard, R. A.; Hurford, G.; Kleint, L.; Kolleck, M.; Krucker, S.;
   Lagg, A.; Landini, F.; Long, D. M.; Lefort, J.; Lodiot, S.; Mampaey,
   B.; Maloney, S.; Marliani, F.; Martinez-Pillet, V.; McMullin, D. R.;
   Müller, D.; Nicolini, G.; Orozco Suarez, D.; Pacros, A.; Pancrazzi,
   M.; Parenti, S.; Peter, H.; Philippon, A.; Plunkett, S.; Rich, N.;
   Rochus, P.; Rouillard, A.; Romoli, M.; Sanchez, L.; Schühle, U.;
   Sidher, S.; Solanki, S. K.; Spadaro, D.; St Cyr, O. C.; Straus, T.;
   Tanco, I.; Teriaca, L.; Thompson, W. T.; del Toro Iniesta, J. C.;
   Verbeeck, C.; Vourlidas, A.; Watson, C.; Wiegelmann, T.; Williams,
   D.; Woch, J.; Zhukov, A. N.; Zouganelis, I.
Bibcode: 2020A&A...642A...6A
Altcode:
  Context. To meet the scientific objectives of the mission, the Solar
  Orbiter spacecraft carries a suite of in-situ (IS) and remote sensing
  (RS) instruments designed for joint operations with inter-instrument
  communication capabilities. Indeed, previous missions have shown that
  the Sun (imaged by the RS instruments) and the heliosphere (mainly
  sampled by the IS instruments) should be considered as an integrated
  system rather than separate entities. Many of the advances expected
  from Solar Orbiter rely on this synergistic approach between IS and
  RS measurements. <BR /> Aims: Many aspects of hardware development,
  integration, testing, and operations are common to two or more
  RS instruments. In this paper, we describe the coordination effort
  initiated from the early mission phases by the Remote Sensing Working
  Group. We review the scientific goals and challenges, and give an
  overview of the technical solutions devised to successfully operate
  these instruments together. <BR /> Methods: A major constraint for the
  RS instruments is the limited telemetry (TM) bandwidth of the Solar
  Orbiter deep-space mission compared to missions in Earth orbit. Hence,
  many of the strategies developed to maximise the scientific return from
  these instruments revolve around the optimisation of TM usage, relying
  for example on onboard autonomy for data processing, compression,
  and selection for downlink. The planning process itself has been
  optimised to alleviate the dynamic nature of the targets, and an
  inter-instrument communication scheme has been implemented which can
  be used to autonomously alter the observing modes. We also outline the
  plans for in-flight cross-calibration, which will be essential to the
  joint data reduction and analysis. <BR /> Results: The RS instrument
  package on Solar Orbiter will carry out comprehensive measurements
  from the solar interior to the inner heliosphere. Thanks to the close
  coordination between the instrument teams and the European Space
  Agency, several challenges specific to the RS suite were identified
  and addressed in a timely manner.

Title: Models and data analysis tools for the Solar Orbiter mission
Authors: Rouillard, A. P.; Pinto, R. F.; Vourlidas, A.; De Groof, A.;
   Thompson, W. T.; Bemporad, A.; Dolei, S.; Indurain, M.; Buchlin, E.;
   Sasso, C.; Spadaro, D.; Dalmasse, K.; Hirzberger, J.; Zouganelis, I.;
   Strugarek, A.; Brun, A. S.; Alexandre, M.; Berghmans, D.; Raouafi,
   N. E.; Wiegelmann, T.; Pagano, P.; Arge, C. N.; Nieves-Chinchilla,
   T.; Lavarra, M.; Poirier, N.; Amari, T.; Aran, A.; Andretta, V.;
   Antonucci, E.; Anastasiadis, A.; Auchère, F.; Bellot Rubio, L.;
   Nicula, B.; Bonnin, X.; Bouchemit, M.; Budnik, E.; Caminade, S.;
   Cecconi, B.; Carlyle, J.; Cernuda, I.; Davila, J. M.; Etesi, L.;
   Espinosa Lara, F.; Fedorov, A.; Fineschi, S.; Fludra, A.; Génot,
   V.; Georgoulis, M. K.; Gilbert, H. R.; Giunta, A.; Gomez-Herrero, R.;
   Guest, S.; Haberreiter, M.; Hassler, D.; Henney, C. J.; Howard, R. A.;
   Horbury, T. S.; Janvier, M.; Jones, S. I.; Kozarev, K.; Kraaikamp,
   E.; Kouloumvakos, A.; Krucker, S.; Lagg, A.; Linker, J.; Lavraud,
   B.; Louarn, P.; Maksimovic, M.; Maloney, S.; Mann, G.; Masson, A.;
   Müller, D.; Önel, H.; Osuna, P.; Orozco Suarez, D.; Owen, C. J.;
   Papaioannou, A.; Pérez-Suárez, D.; Rodriguez-Pacheco, J.; Parenti,
   S.; Pariat, E.; Peter, H.; Plunkett, S.; Pomoell, J.; Raines, J. M.;
   Riethmüller, T. L.; Rich, N.; Rodriguez, L.; Romoli, M.; Sanchez,
   L.; Solanki, S. K.; St Cyr, O. C.; Straus, T.; Susino, R.; Teriaca,
   L.; del Toro Iniesta, J. C.; Ventura, R.; Verbeeck, C.; Vilmer, N.;
   Warmuth, A.; Walsh, A. P.; Watson, C.; Williams, D.; Wu, Y.; Zhukov,
   A. N.
Bibcode: 2020A&A...642A...2R
Altcode:
  Context. The Solar Orbiter spacecraft will be equipped with a wide
  range of remote-sensing (RS) and in situ (IS) instruments to record
  novel and unprecedented measurements of the solar atmosphere and
  the inner heliosphere. To take full advantage of these new datasets,
  tools and techniques must be developed to ease multi-instrument and
  multi-spacecraft studies. In particular the currently inaccessible
  low solar corona below two solar radii can only be observed
  remotely. Furthermore techniques must be used to retrieve coronal
  plasma properties in time and in three dimensional (3D) space. Solar
  Orbiter will run complex observation campaigns that provide interesting
  opportunities to maximise the likelihood of linking IS data to their
  source region near the Sun. Several RS instruments can be directed
  to specific targets situated on the solar disk just days before
  data acquisition. To compare IS and RS, data we must improve our
  understanding of how heliospheric probes magnetically connect to the
  solar disk. <BR /> Aims: The aim of the present paper is to briefly
  review how the current modelling of the Sun and its atmosphere
  can support Solar Orbiter science. We describe the results of a
  community-led effort by European Space Agency's Modelling and Data
  Analysis Working Group (MADAWG) to develop different models, tools,
  and techniques deemed necessary to test different theories for the
  physical processes that may occur in the solar plasma. The focus here
  is on the large scales and little is described with regards to kinetic
  processes. To exploit future IS and RS data fully, many techniques have
  been adapted to model the evolving 3D solar magneto-plasma from the
  solar interior to the solar wind. A particular focus in the paper is
  placed on techniques that can estimate how Solar Orbiter will connect
  magnetically through the complex coronal magnetic fields to various
  photospheric and coronal features in support of spacecraft operations
  and future scientific studies. <BR /> Methods: Recent missions such as
  STEREO, provided great opportunities for RS, IS, and multi-spacecraft
  studies. We summarise the achievements and highlight the challenges
  faced during these investigations, many of which motivated the Solar
  Orbiter mission. We present the new tools and techniques developed
  by the MADAWG to support the science operations and the analysis of
  the data from the many instruments on Solar Orbiter. <BR /> Results:
  This article reviews current modelling and tool developments that ease
  the comparison of model results with RS and IS data made available
  by current and upcoming missions. It also describes the modelling
  strategy to support the science operations and subsequent exploitation
  of Solar Orbiter data in order to maximise the scientific output
  of the mission. <BR /> Conclusions: The on-going community effort
  presented in this paper has provided new models and tools necessary
  to support mission operations as well as the science exploitation of
  the Solar Orbiter data. The tools and techniques will no doubt evolve
  significantly as we refine our procedure and methodology during the
  first year of operations of this highly promising mission.

Title: The Solar Orbiter Science Activity Plan. Translating solar
    and heliospheric physics questions into action
Authors: Zouganelis, I.; De Groof, A.; Walsh, A. P.; Williams, D. R.;
   Müller, D.; St Cyr, O. C.; Auchère, F.; Berghmans, D.; Fludra,
   A.; Horbury, T. S.; Howard, R. A.; Krucker, S.; Maksimovic, M.;
   Owen, C. J.; Rodríguez-Pacheco, J.; Romoli, M.; Solanki, S. K.;
   Watson, C.; Sanchez, L.; Lefort, J.; Osuna, P.; Gilbert, H. R.;
   Nieves-Chinchilla, T.; Abbo, L.; Alexandrova, O.; Anastasiadis, A.;
   Andretta, V.; Antonucci, E.; Appourchaux, T.; Aran, A.; Arge, C. N.;
   Aulanier, G.; Baker, D.; Bale, S. D.; Battaglia, M.; Bellot Rubio,
   L.; Bemporad, A.; Berthomier, M.; Bocchialini, K.; Bonnin, X.; Brun,
   A. S.; Bruno, R.; Buchlin, E.; Büchner, J.; Bucik, R.; Carcaboso,
   F.; Carr, R.; Carrasco-Blázquez, I.; Cecconi, B.; Cernuda Cangas, I.;
   Chen, C. H. K.; Chitta, L. P.; Chust, T.; Dalmasse, K.; D'Amicis, R.;
   Da Deppo, V.; De Marco, R.; Dolei, S.; Dolla, L.; Dudok de Wit, T.;
   van Driel-Gesztelyi, L.; Eastwood, J. P.; Espinosa Lara, F.; Etesi,
   L.; Fedorov, A.; Félix-Redondo, F.; Fineschi, S.; Fleck, B.; Fontaine,
   D.; Fox, N. J.; Gandorfer, A.; Génot, V.; Georgoulis, M. K.; Gissot,
   S.; Giunta, A.; Gizon, L.; Gómez-Herrero, R.; Gontikakis, C.; Graham,
   G.; Green, L.; Grundy, T.; Haberreiter, M.; Harra, L. K.; Hassler,
   D. M.; Hirzberger, J.; Ho, G. C.; Hurford, G.; Innes, D.; Issautier,
   K.; James, A. W.; Janitzek, N.; Janvier, M.; Jeffrey, N.; Jenkins,
   J.; Khotyaintsev, Y.; Klein, K. -L.; Kontar, E. P.; Kontogiannis,
   I.; Krafft, C.; Krasnoselskikh, V.; Kretzschmar, M.; Labrosse, N.;
   Lagg, A.; Landini, F.; Lavraud, B.; Leon, I.; Lepri, S. T.; Lewis,
   G. R.; Liewer, P.; Linker, J.; Livi, S.; Long, D. M.; Louarn, P.;
   Malandraki, O.; Maloney, S.; Martinez-Pillet, V.; Martinovic, M.;
   Masson, A.; Matthews, S.; Matteini, L.; Meyer-Vernet, N.; Moraitis,
   K.; Morton, R. J.; Musset, S.; Nicolaou, G.; Nindos, A.; O'Brien,
   H.; Orozco Suarez, D.; Owens, M.; Pancrazzi, M.; Papaioannou, A.;
   Parenti, S.; Pariat, E.; Patsourakos, S.; Perrone, D.; Peter, H.;
   Pinto, R. F.; Plainaki, C.; Plettemeier, D.; Plunkett, S. P.; Raines,
   J. M.; Raouafi, N.; Reid, H.; Retino, A.; Rezeau, L.; Rochus, P.;
   Rodriguez, L.; Rodriguez-Garcia, L.; Roth, M.; Rouillard, A. P.;
   Sahraoui, F.; Sasso, C.; Schou, J.; Schühle, U.; Sorriso-Valvo, L.;
   Soucek, J.; Spadaro, D.; Stangalini, M.; Stansby, D.; Steller, M.;
   Strugarek, A.; Štverák, Š.; Susino, R.; Telloni, D.; Terasa, C.;
   Teriaca, L.; Toledo-Redondo, S.; del Toro Iniesta, J. C.; Tsiropoula,
   G.; Tsounis, A.; Tziotziou, K.; Valentini, F.; Vaivads, A.; Vecchio,
   A.; Velli, M.; Verbeeck, C.; Verdini, A.; Verscharen, D.; Vilmer, N.;
   Vourlidas, A.; Wicks, R.; Wimmer-Schweingruber, R. F.; Wiegelmann,
   T.; Young, P. R.; Zhukov, A. N.
Bibcode: 2020A&A...642A...3Z
Altcode: 2020arXiv200910772Z
  Solar Orbiter is the first space mission observing the solar plasma
  both in situ and remotely, from a close distance, in and out of the
  ecliptic. The ultimate goal is to understand how the Sun produces
  and controls the heliosphere, filling the Solar System and driving
  the planetary environments. With six remote-sensing and four in-situ
  instrument suites, the coordination and planning of the operations are
  essential to address the following four top-level science questions:
  (1) What drives the solar wind and where does the coronal magnetic field
  originate?; (2) How do solar transients drive heliospheric variability?;
  (3) How do solar eruptions produce energetic particle radiation that
  fills the heliosphere?; (4) How does the solar dynamo work and drive
  connections between the Sun and the heliosphere? Maximising the
  mission's science return requires considering the characteristics
  of each orbit, including the relative position of the spacecraft
  to Earth (affecting downlink rates), trajectory events (such
  as gravitational assist manoeuvres), and the phase of the solar
  activity cycle. Furthermore, since each orbit's science telemetry
  will be downloaded over the course of the following orbit, science
  operations must be planned at mission level, rather than at the level
  of individual orbits. It is important to explore the way in which those
  science questions are translated into an actual plan of observations
  that fits into the mission, thus ensuring that no opportunities are
  missed. First, the overarching goals are broken down into specific,
  answerable questions along with the required observations and the
  so-called Science Activity Plan (SAP) is developed to achieve this. The
  SAP groups objectives that require similar observations into Solar
  Orbiter Observing Plans, resulting in a strategic, top-level view of
  the optimal opportunities for science observations during the mission
  lifetime. This allows for all four mission goals to be addressed. In
  this paper, we introduce Solar Orbiter's SAP through a series of
  examples and the strategy being followed.

Title: The Polarimetric and Helioseismic Imager on Solar Orbiter
Authors: Solanki, S. K.; del Toro Iniesta, J. C.; Woch, J.; Gandorfer,
   A.; Hirzberger, J.; Alvarez-Herrero, A.; Appourchaux, T.; Martínez
   Pillet, V.; Pérez-Grande, I.; Sanchis Kilders, E.; Schmidt, W.;
   Gómez Cama, J. M.; Michalik, H.; Deutsch, W.; Fernandez-Rico, G.;
   Grauf, B.; Gizon, L.; Heerlein, K.; Kolleck, M.; Lagg, A.; Meller, R.;
   Müller, R.; Schühle, U.; Staub, J.; Albert, K.; Alvarez Copano, M.;
   Beckmann, U.; Bischoff, J.; Busse, D.; Enge, R.; Frahm, S.; Germerott,
   D.; Guerrero, L.; Löptien, B.; Meierdierks, T.; Oberdorfer, D.;
   Papagiannaki, I.; Ramanath, S.; Schou, J.; Werner, S.; Yang, D.;
   Zerr, A.; Bergmann, M.; Bochmann, J.; Heinrichs, J.; Meyer, S.;
   Monecke, M.; Müller, M. -F.; Sperling, M.; Álvarez García, D.;
   Aparicio, B.; Balaguer Jiménez, M.; Bellot Rubio, L. R.; Cobos
   Carracosa, J. P.; Girela, F.; Hernández Expósito, D.; Herranz, M.;
   Labrousse, P.; López Jiménez, A.; Orozco Suárez, D.; Ramos, J. L.;
   Barandiarán, J.; Bastide, L.; Campuzano, C.; Cebollero, M.; Dávila,
   B.; Fernández-Medina, A.; García Parejo, P.; Garranzo-García, D.;
   Laguna, H.; Martín, J. A.; Navarro, R.; Núñez Peral, A.; Royo, M.;
   Sánchez, A.; Silva-López, M.; Vera, I.; Villanueva, J.; Fourmond,
   J. -J.; de Galarreta, C. Ruiz; Bouzit, M.; Hervier, V.; Le Clec'h,
   J. C.; Szwec, N.; Chaigneau, M.; Buttice, V.; Dominguez-Tagle, C.;
   Philippon, A.; Boumier, P.; Le Cocguen, R.; Baranjuk, G.; Bell,
   A.; Berkefeld, Th.; Baumgartner, J.; Heidecke, F.; Maue, T.; Nakai,
   E.; Scheiffelen, T.; Sigwarth, M.; Soltau, D.; Volkmer, R.; Blanco
   Rodríguez, J.; Domingo, V.; Ferreres Sabater, A.; Gasent Blesa,
   J. L.; Rodríguez Martínez, P.; Osorno Caudel, D.; Bosch, J.; Casas,
   A.; Carmona, M.; Herms, A.; Roma, D.; Alonso, G.; Gómez-Sanjuan, A.;
   Piqueras, J.; Torralbo, I.; Fiethe, B.; Guan, Y.; Lange, T.; Michel,
   H.; Bonet, J. A.; Fahmy, S.; Müller, D.; Zouganelis, I.
Bibcode: 2020A&A...642A..11S
Altcode: 2019arXiv190311061S
  <BR /> Aims: This paper describes the Polarimetric and Helioseismic
  Imager on the Solar Orbiter mission (SO/PHI), the first magnetograph and
  helioseismology instrument to observe the Sun from outside the Sun-Earth
  line. It is the key instrument meant to address the top-level science
  question: How does the solar dynamo work and drive connections between
  the Sun and the heliosphere? SO/PHI will also play an important role
  in answering the other top-level science questions of Solar Orbiter,
  while hosting the potential of a rich return in further science. <BR
  /> Methods: SO/PHI measures the Zeeman effect and the Doppler shift
  in the Fe I 617.3 nm spectral line. To this end, the instrument
  carries out narrow-band imaging spectro-polarimetry using a tunable
  LiNbO<SUB>3</SUB> Fabry-Perot etalon, while the polarisation modulation
  is done with liquid crystal variable retarders. The line and the nearby
  continuum are sampled at six wavelength points and the data are recorded
  by a 2k × 2k CMOS detector. To save valuable telemetry, the raw data
  are reduced on board, including being inverted under the assumption of
  a Milne-Eddington atmosphere, although simpler reduction methods are
  also available on board. SO/PHI is composed of two telescopes; one,
  the Full Disc Telescope, covers the full solar disc at all phases of
  the orbit, while the other, the High Resolution Telescope, can resolve
  structures as small as 200 km on the Sun at closest perihelion. The high
  heat load generated through proximity to the Sun is greatly reduced by
  the multilayer-coated entrance windows to the two telescopes that allow
  less than 4% of the total sunlight to enter the instrument, most of
  it in a narrow wavelength band around the chosen spectral line. <BR />
  Results: SO/PHI was designed and built by a consortium having partners
  in Germany, Spain, and France. The flight model was delivered to
  Airbus Defence and Space, Stevenage, and successfully integrated into
  the Solar Orbiter spacecraft. A number of innovations were introduced
  compared with earlier space-based spectropolarimeters, thus allowing
  SO/PHI to fit into the tight mass, volume, power and telemetry budgets
  provided by the Solar Orbiter spacecraft and to meet the (e.g. thermal)
  challenges posed by the mission's highly elliptical orbit.

Title: PMI: The Photospheric Magnetic Field Imager
Authors: Staub, Jan; Fernandez-Rico, German; Gandorfer, Achim; Gizon,
   Laurent; Hirzberger, Johann; Kraft, Stefan; Lagg, Andreas; Schou,
   Jesper; Solanki, Sami K.; del Toro Iniesta, Jose Carlos; Wiegelmann,
   Thomas; Woch, Joachim
Bibcode: 2020JSWSC..10...54S
Altcode:
  We describe the design and the capabilities of the Photospheric Magnetic
  field Imager (PMI), a compact and lightweight vector magnetograph,
  which is being developed for ESA's Lagrange mission to the Lagrange
  L5 point. After listing the design requirements and give a scientific
  justification for them, we describe the technical implementation and
  the design solution capable of fulfilling these requirements. This is
  followed by a description of the hardware architecture as well as the
  operations principle. An outlook on the expected performance concludes
  the paper.

Title: Helicity proxies from linear polarisation of solar active
    regions
Authors: Prabhu, A.; Brandenburg, A.; Käpylä, M. J.; Lagg, A.
Bibcode: 2020A&A...641A..46P
Altcode: 2020arXiv200110884P
  Context. The α effect is believed to play a key role in the
  generation of the solar magnetic field. A fundamental test for its
  significance in the solar dynamo is to look for magnetic helicity of
  opposite signs both between the two hemispheres as well as between
  small and large scales. However, measuring magnetic helicity is
  compromised by the inability to fully infer the magnetic field vector
  from observations of solar spectra, caused by what is known as the
  π ambiguity of spectropolarimetric observations. <BR /> Aims: We
  decompose linear polarisation into parity-even and parity-odd E and B
  polarisations, which are not affected by the π ambiguity. Furthermore,
  we study whether the correlations of spatial Fourier spectra of B and
  parity-even quantities such as E or temperature T are a robust proxy for
  magnetic helicity of solar magnetic fields. <BR /> Methods: We analysed
  polarisation measurements of active regions observed by the Helioseismic
  and Magnetic Imager on board the Solar Dynamics observatory. Theory
  predicts the magnetic helicity of active regions to have, statistically,
  opposite signs in the two hemispheres. We then computed the parity-odd
  EB and TB correlations and tested for a systematic preference of
  their sign based on the hemisphere of the active regions. <BR />
  Results: We find that: (i) EB and TB correlations are a reliable
  proxy for magnetic helicity, when computed from linear polarisation
  measurements away from spectral line cores; and (ii) E polarisation
  reverses its sign close to the line core. Our analysis reveals that
  Faraday rotation does not have a significant influence on the computed
  parity-odd correlations. <BR /> Conclusions: The EB decomposition of
  linear polarisation appears to be a good proxy for magnetic helicity
  independent of the π ambiguity. This allows us to routinely infer
  magnetic helicity directly from polarisation measurements.

Title: No universal connection between the vertical magnetic field
    and the umbra-penumbra boundary in sunspots
Authors: Löptien, B.; Lagg, A.; van Noort, M.; Solanki, S. K.
Bibcode: 2020A&A...639A.106L
Altcode: 2020arXiv200602346L
  Context. It has been reported that the boundary between the umbra and
  the penumbra of sunspots occurs at a canonical value of the strength
  of the vertical magnetic field, independently of the size of the
  spot. This critical field strength is interpreted to be the threshold
  for the onset of magnetoconvection. <BR /> Aims: Here we investigate
  the reasons why this criterion, also called the Jurčák criterion
  in the literature, does not always identify the boundary between the
  umbra and the penumbra. <BR /> Methods: We performed a statistical
  analysis of 23 sunspots observed with Hinode/SOT. We compared the
  properties of the continuum intensity and the vertical magnetic
  field between filaments and spines and how they vary between spots of
  different sizes. <BR /> Results: We find that the inner boundary of the
  penumbra is not related to a universal value of the vertical magnetic
  field. The properties of spines and filaments vary between spots of
  different sizes. Both components are darker in larger spots and the
  spines exhibit a stronger vertical magnetic field. These variations of
  the properties of filaments and spines with the spot size are also the
  reason for the reported invariance in the averaged vertical magnetic
  field at 50% of the mean continuum intensity. <BR /> Conclusions:
  The formation of filaments and the onset of magnetoconvection are not
  related to a canonical value of the strength of the vertical magnetic
  field. The seemingly unique magnetic field strength is rather an effect
  of the filling factor of spines and penumbral filaments.

Title: Detection of the Strongest Magnetic Field in a Sunspot
    Light Bridge
Authors: Castellanos Durán, J. S.; Lagg, Andreas; Solanki, Sami K.;
   van Noort, Michiel
Bibcode: 2020ApJ...895..129C
Altcode: 2020arXiv200312078C; 2020ApJ...895..129D
  Traditionally, the strongest magnetic fields on the Sun have been
  measured in sunspot umbrae. More recently, however, much stronger
  fields have been measured at the ends of penumbral filaments carrying
  the Evershed and counter-Evershed flows. Superstrong fields have
  also been reported within a light bridge separating two umbrae of
  opposite polarities. We aim to accurately determine the strengths of the
  strongest fields in a light bridge using an advanced inversion technique
  and to investigate their detailed structure. We analyze observations
  from the spectropolarimeter on board the Hinode spacecraft of the
  active region AR 11967. The thermodynamic and magnetic configurations
  are obtained by inverting the Stokes profiles using an inversion scheme
  that allows multiple height nodes. Both the traditional 1D inversion
  technique and the so-called 2D coupled inversions, which take into
  account the point-spread function of the Hinode telescope, are used. We
  find a compact structure with an area of 32.7 arcsec<SUP>2</SUP> within
  a bipolar light bridge with field strengths exceeding 5 kG, confirming
  the strong fields in this light bridge reported in the literature. Two
  regions associated with downflows of ∼5 km s<SUP>-1</SUP> harbor
  field strengths larger than 6.5 kG, covering a total area of 2.97
  arcsec<SUP>2</SUP>. The maximum field strength found is 8.2 kG, which
  is the largest ever observed field in a bipolar light bridge up to now.

Title: Connecting the Wilson depression to the magnetic field
    of sunspots
Authors: Löptien, B.; Lagg, A.; van Noort, M.; Solanki, S. K.
Bibcode: 2020A&A...635A.202L
Altcode: 2020arXiv200207484L
  Context. In sunspots, the geometric height of continuum optical depth
  unity is depressed compared to the quiet Sun. This so-called Wilson
  depression is caused by the Lorentz force of the strong magnetic
  field inside the spots. However, it is not understood in detail yet
  how the Wilson depression is related to the strength and geometry
  of the magnetic field or to other properties of the sunspot. <BR />
  Aims: We aim to study the dependence of the Wilson depression on the
  properties of the magnetic field of the sunspots and how exactly the
  magnetic field contributes to balancing the Wilson depression with
  respect to the gas pressure of the surroundings of the spots. <BR
  /> Methods: Our study is based on 24 spectropolarimetric scans of
  12 individual sunspots performed with Hinode. We derived the Wilson
  depression for each spot using both a recently developed method that
  is based on minimizing the divergence of the magnetic field and an
  approach that was developed earlier, which enforces an equilibrium
  between the gas pressure and the magnetic pressure inside the spot and
  the gas pressure in the quiet Sun, thus neglecting the influence of the
  curvature force. We then performed a statistical analysis by comparing
  the Wilson depression resulting from the two techniques with each other
  and by relating them to various parameters of the sunspots, such as
  their size or the strength of the magnetic field. <BR /> Results: We
  find that the Wilson depression becomes larger for spots with a stronger
  magnetic field, but not as much as one would expect from the increased
  magnetic pressure. This suggests that the curvature integral provides
  an important contribution to the Wilson depression, particularly
  for spots with a weak magnetic field. Our results indicate that the
  geometry of the magnetic field in the penumbra is different between
  spots with different strengths of the average umbral magnetic field.

Title: Fast downflows in a chromospheric filament
Authors: Sowmya, K.; Lagg, A.; Solanki, S. K.; Castellanos Durán,
   J. S.
Bibcode: 2020IAUS..354..454S
Altcode: 2019arXiv191206586S
  An active region filament in the upper chromosphere is studied using
  spectropolarimetric data in He i 10830 Å from the GREGOR telescope. A
  Milne-Eddingon based inversion of the Unno-Rachkovsky equations is
  used to retrieve the velocity and the magnetic field vector of the
  region. The plasma velocity reaches supersonic values closer to the feet
  of the filament barbs and coexist with a slow velocity component. Such
  supersonic velocities result from the acceleration of the plasma as it
  drains from the filament spine through the barbs. The line-of-sight
  magnetic fields have strengths below 200 G in the filament spine and
  in the filament barbs where fast downflows are located, their strengths
  range between 100 - 700 G.

Title: Superstrong photospheric magnetic fields in sunspot penumbrae
Authors: Siu-Tapia, A.; Lagg, A.; van Noort, M.; Rempel, M.; Solanki,
   S. K.
Bibcode: 2019A&A...631A..99S
Altcode: 2019arXiv190913619S
  Context. Recently, there have been some reports of unusually strong
  photospheric magnetic fields (which can reach values of over 7 kG)
  inferred from Hinode SOT/SP sunspot observations within penumbral
  regions. These superstrong penumbral fields are even larger than the
  strongest umbral fields on record and appear to be associated with
  supersonic downflows. The finding of such fields has been controversial
  since they seem to show up only when spatially coupled inversions
  are performed. <BR /> Aims: Here, we investigate and discuss the
  reliability of those findings by studying in detail observed spectra
  associated with particularly strong magnetic fields at the inner edge
  of the penumbra of active region 10930. <BR /> Methods: We applied
  classical diagnostic methods and various inversions with different
  model atmospheres to the observed Stokes profiles in two selected
  pixels with superstrong magnetic fields, and compared the results
  with a magnetohydrodynamic simulation of a sunspot whose penumbra
  contains localized regions with strong fields (nearly 5 kG at τ = 1)
  associated with supersonic downflows. <BR /> Results: The different
  inversions provide different results: while the SPINOR 2D inversions
  consider a height-dependent single-component model and return B &gt;
  7 kG and supersonic positive v<SUB>LOS</SUB> (corresponding to a
  counter-Evershed flow), height-dependent two-component inversions
  suggest the presence of an umbral component (almost at rest)
  with field strengths ∼4 - 4.2 kG and a penumbral component with
  v<SUB>LOS</SUB> ∼ 16 - 18 km s<SUP>-1</SUP> and field strengths up
  to ∼5.8 kG. Likewise, height-independent two-component inversions
  find a solution for an umbral component and a strongly redshifted
  (v<SUB>LOS</SUB> ∼ 15 - 17 km s<SUP>-1</SUP>) penumbral component
  with B ∼ 4 kG. According to a Bayesian information criterion,
  the inversions providing a better balance between the quality of
  the fits and the number of free parameters considered by the models
  are the height-independent two-component inversions, but they lie
  only slightly above the SPINOR 2D inversions. Since it is expected
  that the physical parameters all display considerable gradients with
  height, as supported by magnetohydrodynamic (MHD) sunspot simulations,
  the SPINOR 2D inversions are the preferred ones. <BR /> Conclusions:
  According to the MHD sunspot simulation analyzed here, the presence
  of counter-Evershed flows in the photospheric penumbra can lead to
  the necessary conditions for the observation of ∼5 kG fields at the
  inner penumbra. Although a definite conclusion about the potential
  existence of fields in excess of 7 kG cannot be given, their nature
  could be explained (based on the simulation results) as the consequence
  of the extreme dynamical effects introduced by highly supersonic
  counter-Evershed flows (v<SUB>LOS</SUB> &gt; 10 km s<SUP>-1</SUP>
  and up to ∼30 km s<SUP>-1</SUP> according to SPINOR 2D). The latter
  are much faster and more compressive downflows than those found in
  the MHD simulations and therefore could lead to field intensification
  up to considerably stronger fields. Also, a lower gas density would
  lead to a deeper depression of the τ = 1 surface, making possible
  the observation of deeper-lying stronger fields. The superstrong
  magnetic fields are expected to be nearly force-free, meaning that
  they can attain much larger strengths than expected when considering
  only balance between magnetic pressure and the local gas pressure.

Title: A comparison between solar plage and network properties
Authors: Buehler, D.; Lagg, A.; van Noort, M.; Solanki, S. K.
Bibcode: 2019A&A...630A..86B
Altcode: 2019arXiv190807464B
  <BR /> Aims: We compare the properties of kG magnetic structures
  in the solar network and in active region plage at high spatial
  resolution. <BR /> Methods: Our analysis used six SP scans of the solar
  disc centre aboard Hinode SOT and inverted the obtained spectra of the
  photospheric 6302 Å line pair using the 2D SPINOR code. <BR /> Results:
  Photospheric magnetic field concentrations in network and plage areas
  are on average 1.5 kG strong with inclinations of 10° -20°, and have
  &lt; 400 m s<SUP>-1</SUP> internal and 2-3 km s<SUP>-1</SUP> external
  downflows. At the disc centre, the continuum intensity of magnetic
  field concentrations in the network are on average 10% brighter than the
  mean quiet Sun, whilst their plage counterparts are 3% darker. A more
  detailed analysis revealed that all sizes of individual kG patches in
  the network have 150 G higher field strengths on average, 5% higher
  continuum contrasts, and 800 m s<SUP>-1</SUP> faster surrounding
  downflows than similarly sized patches in the plage. The speed of
  the surrounding downflows also correlates with the patch area, and
  patches containing pores can produce supersonic flows exceeding 11 km
  s<SUP>-1</SUP> in individual pixels. Furthermore, the magnetic canopies
  of kG patches are on average 9° more horizontal in the plage compared
  to the network. <BR /> Conclusions: Most of the differences between the
  network and plage are due to their different patch size distributions,
  but the intrinsic differences between similarly sized patches likely
  results from the modification of the convection photospheric convection
  with increasing amounts of magnetic flux.

Title: Performance Analysis of the SO/PHI Software Framework for
    On-board Data Reduction
Authors: Albert, K.; Hirzberger, J.; Busse, D.; Rodríguez, J. Blanco;
   Castellanos Duran, J. S.; Cobos Carrascosa, J. P.; Fiethe, B.;
   Gandorfer, A.; Guan, Y.; Kolleck, M.; Lagg, A.; Lange, T.; Michalik,
   H.; Solanki, S. K.; del Toro Iniesta, J. C.
Bibcode: 2019ASPC..523..151A
Altcode: 2019arXiv190508690A
  The Polarimetric and Helioseismic Imager (PHI) is the first deep-space
  solar spectropolarimeter, on-board the Solar Orbiter (SO) space
  mission. It faces: stringent requirements on science data accuracy, a
  dynamic environment, and severe limitations on telemetry volume. SO/PHI
  overcomes these restrictions through on-board instrument calibration
  and science data reduction, using dedicated firmware in FPGAs. This
  contribution analyses the accuracy of a data processing pipeline by
  comparing the results obtained with SO/PHI hardware to a reference
  from a ground computer. The results show that for the analyzed pipeline
  the error introduced by the firmware implementation is well below the
  requirements of SO/PHI.

Title: Using the infrared iron lines to probe solar subsurface
    convection
Authors: Milić, I.; Smitha, H. N.; Lagg, A.
Bibcode: 2019A&A...630A.133M
Altcode: 2019arXiv190407306M
  Context. Studying the properties of solar convection using
  high-resolution spectropolarimetry began in the early 1990s with
  the focus on observations in the visible wavelength regions. Its
  extension to the infrared (IR) remains largely unexplored. <BR />
  Aims: The IR iron lines around 15 600 Å, most commonly known for
  their high magnetic sensitivity, also have a non-zero response to
  line-of-sight (LOS) velocity below log(τ) = 0.0. In this paper we
  explore the possibility of using these lines to measure subsurface
  convective velocities. <BR /> Methods: By assuming a snapshot of a
  three-dimensional magnetohydrodynamic simulation to represent the quiet
  Sun, we investigate how well the iron IR lines can reproduce the LOS
  velocity in the cube and to what depth. We use the recently developed
  spectropolarimetric inversion code SNAPI and discuss the optimal node
  placements for the retrieval of reliable results from these spectral
  lines. <BR /> Results: We find that the IR iron lines can measure the
  convective velocities down to log(τ) = 0.5, below the photosphere,
  not only at the original resolution of the cube, but also when degraded
  with a reasonable spectral and spatial PSF and stray light. Instead, the
  commonly used Fe I 6300 Å line pair performs significantly worse. <BR
  /> Conclusions: Our investigation reveals that the IR iron lines can
  probe the subsurface convection in the solar photosphere. This paper
  is a first step towards exploiting this diagnostic potential.

Title: Moving Magnetic Features around a Pore
Authors: Kaithakkal, A.; Riethmueller, T.; Solanki, S. K.; Lagg, A.
Bibcode: 2019ASPC..526..307K
Altcode:
  Moving magnetic features (MMFs) are small-scale magnetic elements
  observed to move radially outward from sunspots. Some studies have
  reported the presence of MMFs around pores as well. We analyzed data
  from SunriseII/IMaX observations obtained on 2013 June 12 between
  23:39:10 and 23:55:37 UT. IMaX scanned the Fe I 5250.225 Å spectral
  line at eight wavelength positions and recorded the full Stokes vector
  at each of these positions. The field of view covered a large pore
  (μ = 0.93) with pixel scale of 0″.055. MMFs of opposite (positive)
  and same (negative) polarity as the pore were observed to stream
  from the pore boundary. We carried out a statistical analysis of the
  physical properties of MMFs and the main results are: 1) the number
  of opposite polarity MMFs within 1.5 Mm from the pore border, when
  they were first identified, is twice that of the same polarity MMFs. 2)
  Only 11% of the chosen MMFs appear to be monopolar and they all have the
  same polarity as the pore. 3) Majority of MMFs of both polarities move
  away from the pore border with an average speed of 1.5 km/s. However,
  they do not always follow a smooth radial track and some of them even
  move in tangential direction to the pore. 4) MMFs of opposite polarity
  show a preferential up-flow whereas those of the same polarity do not
  show any preference. 5) MMFs of both polarities are characterized by
  inclined fields. <P />This work, presented in an oral contribution
  at this Workshop, has been published on The Astrophysical Journal
  Supplement Series (Kaithakkal et al. 2017).

Title: Photospheric Magnetic Fields of the Trailing Sunspots in
    Active Region NOAA 12396
Authors: Verma, M.; Balthasar, H.; Denker, C.; Böhm, F.; Fischer,
   C. E.; Kuckein, C.; González Manrique, S. J.; Sobotka, M.; Bello
   González, N.; Diercke, A.; Berkefeld, T.; Collados, M.; Feller, A.;
   Hofmann, A.; Lagg, A.; Nicklas, H.; Orozco Suárez, D.; Pastor Yabar,
   A.; Rezaei, R.; Schlichenmaier, R.; Schmidt, D.; Schmidt, W.; Sigwarth,
   M.; Solanki, S. K.; Soltau, D.; Staude, J.; Strassmeier, K.; Volkmer,
   R.; von der Lühe, O.; Waldmann, T.
Bibcode: 2019ASPC..526..291V
Altcode: 2018arXiv180507752V
  The solar magnetic field is responsible for all aspects of solar
  activity. Sunspots are the main manifestation of the ensuing solar
  activity. Combining high-resolution and synoptic observations has
  the ambition to provide a comprehensive description of the sunspot
  growth and decay processes. Active region NOAA 12396 emerged on 2015
  August 3 and was observed three days later with the 1.5-meter GREGOR
  solar telescope on 2015 August 6. High-resolution spectropolarimetric
  data from the GREGOR Infrared Spectrograph (GRIS) are obtained in the
  photospheric lines Si I λ1082.7 nm and Ca I λ1083.9 nm, together
  with the chromospheric He I λ1083.0 nm triplet. These near-infrared
  spectropolarimetric observations were complemented by synoptic
  line-of-sight magnetograms and continuum images of the Helioseismic
  and Magnetic Imager (HMI) and EUV images of the Atmospheric Imaging
  Assembly (AIA) on board the Solar Dynamics Observatory (SDO).

Title: Measuring the Wilson depression of sunspots using the
    divergence-free condition of the magnetic field vector
Authors: Löptien, B.; Lagg, A.; van Noort, M.; Solanki, S. K.
Bibcode: 2018A&A...619A..42L
Altcode: 2018arXiv180806867L
  Context. The Wilson depression is the difference in geometric height of
  unit continuum optical depth between the sunspot umbra and the quiet
  Sun. Measuring the Wilson depression is important for understanding
  the geometry of sunspots. Current methods suffer from systematic
  effects or need to make assumptions on the geometry of the magnetic
  field. This leads to large systematic uncertainties of the derived
  Wilson depressions. <BR /> Aims: We aim to develop a robust method
  for deriving the Wilson depression that only requires the information
  about the magnetic field that is accessible from spectropolarimetry,
  and that does not rely on assumptions on the geometry of sunspots
  or on their magnetic field. <BR /> Methods: Our method is based on
  minimizing the divergence of the magnetic field vector derived from
  spectropolarimetric observations. We have focused on large spatial
  scales only in order to reduce the number of free parameters. <BR />
  Results: We tested the performance of our method using synthetic Hinode
  data derived from two sunspot simulations. We find that the maximum and
  the umbral averaged Wilson depression for both spots determined with
  our method typically lies within 100 km of the true value obtained
  from the simulations. In addition, we applied the method to Hinode
  observations of a sunspot. The derived Wilson depression (∼600 km) is
  consistent with results typically obtained from the Wilson effect. We
  also find that the Wilson depression obtained from using horizontal
  force balance gives 110-180 km smaller Wilson depressions than both,
  what we find and what we deduce directly from the simulations. This
  suggests that the magnetic pressure and the magnetic curvature force
  contribute to the Wilson depression by a similar amount.

Title: SOPHISM: Software Instrument Simulator
Authors: Blanco Rodríguez, J.; del Toro Iniesta, J. C.; Orozco
   Suárez, D.; Martínez Pillet, V.; Bonet, J. A.; Feller, A.;
   Hirzberger, J.; Lagg, A.; Piqueras, J.; Gasent Blesa, J. L.
Bibcode: 2018ascl.soft10017B
Altcode:
  SOPHISM models astronomical instrumentation from the entrance
  of the telescope to data acquisition at the detector, along with
  software blocks dealing with, for example, demodulation, inversion,
  and compression. The code performs most analyses done with light
  in astronomy, such as differential photometry, spectroscopy, and
  polarimetry. The simulator offers flexibility and implementation of new
  effects and subsystems, making it user-adaptable for a wide variety
  of instruments. SOPHISM can be used for all stages of instrument
  definition, design, operation, and lifetime tracking evaluation.

Title: Temporal evolution of arch filaments as seen in He I 10 830 Å
Authors: González Manrique, S. J.; Kuckein, C.; Collados, M.; Denker,
   C.; Solanki, S. K.; Gömöry, P.; Verma, M.; Balthasar, H.; Lagg,
   A.; Diercke, A.
Bibcode: 2018A&A...617A..55G
Altcode: 2018arXiv180700728G
  <BR /> Aims: We study the evolution of an arch filament system (AFS)
  and of its individual arch filaments to learn about the processes
  occurring in them. <BR /> Methods: We observed the AFS at the
  GREGOR solar telescope on Tenerife at high cadence with the very
  fast spectroscopic mode of the GREGOR Infrared Spectrograph (GRIS)
  in the He I 10 830 Å spectral range. The He I triplet profiles
  were fitted with analytic functions to infer line-of-sight (LOS)
  velocities to follow plasma motions within the AFS. <BR /> Results:
  We tracked the temporal evolution of an individual arch filament
  over its entire lifetime, as seen in the He I 10 830 Å triplet. The
  arch filament expanded in height and extended in length from 13″ to
  21″. The lifetime of this arch filament is about 30 min. About 11
  min after the arch filament is seen in He I, the loop top starts to
  rise with an average Doppler velocity of 6 km s<SUP>-1</SUP>. Only two
  minutes later, plasma drains down with supersonic velocities towards
  the footpoints reaching a peak velocity of up to 40 km s<SUP>-1</SUP>
  in the chromosphere. The temporal evolution of He I 10 830 Å profiles
  near the leading pore showed almost ubiquitous dual red components of
  the He I triplet, indicating strong downflows, along with material
  nearly at rest within the same resolution element during the whole
  observing time. <BR /> Conclusions: We followed the arch filament as it
  carried plasma during its rise from the photosphere to the corona. The
  material then drained toward the photosphere, reaching supersonic
  velocities, along the legs of the arch filament. Our observational
  results support theoretical AFS models and aids in improving future
  models. <P />The movie associated to Fig. 3 is available at <A
  href="https://www.aanda.org/10.1051/0004-6361/201832684/olm">https://www.aanda.org/</A>

Title: SOPHISM: An End-to-end Software Instrument Simulator
Authors: Blanco Rodríguez, J.; del Toro Iniesta, J. C.; Orozco
   Suárez, D.; Martínez Pillet, V.; Bonet, J. A.; Feller, A.;
   Hirzberger, J.; Lagg, A.; Piqueras, J.; Gasent Blesa, J. L.
Bibcode: 2018ApJS..237...35B
Altcode:
  We present a software simulator for the modeling of astronomical
  instrumentation, which includes platform effects and software
  processing. It is an end-to-end simulator, from the entrance of
  the telescope to the data acquisition at the detector, along with
  software blocks dealing, e.g., with demodulation, inversion, and
  compression. Developed following the Solar Orbiter/Polarimetric
  and Helioseismic Imager (SO/PHI) instrument, it comprises elements
  such as a filtergraph, polarimetric modulator, detector, vibrations,
  and accumulations. Through these, the simulator performs most of the
  analyses that can be done with light in astronomy, such as differential
  photometry, spectroscopy, and polarimetry. The simulator is coded
  with high flexibility and ease of implementation of new effects and
  subsystems. Thus, it allows for the user to adapt it to a wide variety
  of instruments, even not exclusively solar ones, as illustrated with
  an example of application to a night-time observation. The simulator
  can provide support in the phase of instrument design and help assess
  tolerances and test solutions to underperformances arising during the
  instrument operations. All this makes SOPHISM a very valuable tool
  for all the stages of astronomical instrument definition, design,
  operation, and lifetime tracking evaluation.

Title: Bihelical Spectrum of Solar Magnetic Helicity and Its Evolution
Authors: Singh, Nishant K.; Käpylä, Maarit J.; Brandenburg, Axel;
   Käpylä, Petri J.; Lagg, Andreas; Virtanen, Ilpo
Bibcode: 2018ApJ...863..182S
Altcode: 2018arXiv180404994S
  Using a recently developed two-scale formalism to determine the
  magnetic helicity spectrum, we analyze synoptic vector magnetograms
  built with data from the Vector Spectromagnetograph instrument on the
  Synoptic Optical Long-term Investigations of the Sun telescope during
  2010 January-2016 July. In contrast to an earlier study using only
  three Carrington rotations (CRs), our analysis includes 74 synoptic
  CR maps. We recover here bihelical spectra at different phases of
  solar cycle 24, where the net magnetic helicity in the majority of the
  data is consistent with a large-scale dynamo with helical turbulence
  operating in the Sun. More than 20% of the analyzed maps, however,
  show violations of the expected sign rule.

Title: Getting Ready for the Third Science Flight of SUNRISE
Authors: Barthol, Peter; Katsukawa, Yukio; Lagg, Andreas; Solanki,
   Sami K.; Kubo, Masahito; Riethmueller, Tino; Martínez Pillet,
   Valentin; Gandorfer, Achim; Feller, Alex; Berkefeld, . Thomas; Orozco
   Suárez, David; Del Toro Iniesta, Jose Carlos; Bernasconi, Pietro;
   Álvarez-Herrero, Alberto; Quintero Noda, Carlos
Bibcode: 2018cosp...42E.215B
Altcode:
  SUNRISE is a balloon-borne, stratospheric solar observatory dedicated
  to the investigation of the structure and dynamics of the Sun's
  magnetic field and its interaction with convective plasma flows and
  waves. The previous science flights of SUNRISE in 2009 and 2013 have
  led to many new scientific results, so far described in around 90
  refereed publications. This success has shown the huge potential of the
  SUNRISE concept and the recovery of the largely intact payload offers
  the opportunity for a third flight.The scientific instrumentation of
  SUNRISE 3 will have extended capabilities in particular to measure
  magnetic fields, plasma velocities and temperatures with increased
  sensitivity and over a larger height range in the solar atmosphere, from
  the convectively dominated photosphere up to the still poorly understood
  chromosphere. The latter is the key interaction region between magnetic
  field, waves and radiation and plays a central role in transporting
  energy to the outer layers of the solar atmosphere including the
  corona.SUNRISE 3 will carry 2 new grating-based spectro-polarimeters
  with slit-scanning and context imaging with slitjaw cameras. The
  SUNRISE UV Spectro-polarimeter and Imager (SUSI) will explore the rich
  near-UV range between 300 nm and 430 nm which is poorly accessible
  from the ground. The SUNRISE Chromospheric Infrared spectro-Polarimeter
  (SCIP) will sample 2 spectral windows in the near-infrared, containing
  many spectral lines highly sensitive to magnetic fields at different
  formation heights. In addition to the two new instruments the Imaging
  Magnetograph eXperiment (IMaX), an etalon-based tunable filtergraph and
  spectro-polarimeter flown on both previous missions, will be upgraded
  to IMaX+, enhancing its cadence and giving access to 2 spectral lines
  in the visible spectral range. All three instruments will allow
  investigating both the photosphere and the chromosphere and will
  ideally complement each other in terms of sensitivity, height coverage
  and resolution.A new gondola with a sophisticated attitude control
  system including roll damping will provide improved pointing/tracking
  performance. Upgraded image stabilization with higher bandwidth will
  further reduce residual jitter, maximizing the quality of the science
  data.SUNRISE 3 is a joint project of the German Max-Planck-Institut für
  Sonnensystemforschung together with the Spanish SUNRISE consortium, the
  Johns Hopkins University Applied Physics Laboratory, USA, the German
  Kiepenheuer Institut für Sonnenphysik, the National Astronomical
  Observatory of Japan and the Japan Aerospace eXploraion Agency (JAXA).

Title: Measurements of Photospheric and Chromospheric Magnetic Fields
Authors: Lagg, Andreas; Lites, Bruce; Harvey, Jack; Gosain, Sanjay;
   Centeno, Rebecca
Bibcode: 2018smf..book...37L
Altcode:
  No abstract at ADS

Title: Evershed and Counter-Evershed Flows in Sunspot MHD Simulations
Authors: Siu-Tapia, A. L.; Rempel, M.; Lagg, A.; Solanki, S. K.
Bibcode: 2018ApJ...852...66S
Altcode: 2017arXiv171201202S
  There have been a few reports in the literature of counter-Evershed
  flows observed in well-developed sunspot penumbrae, i.e., flows
  directed toward the umbra along penumbral filaments. Here, we
  investigate the driving forces of such counter-Evershed flows in a
  radiative magnetohydrodynamic simulation of a sunspot, and compare
  them to the forces acting on the normal Evershed flow. The simulation
  covers a timespan of 100 solar hours and generates an Evershed outflow
  exceeding 8 km s<SUP>-1</SUP> in the penumbra along radially aligned
  filaments where the magnetic field is almost horizontal. Additionally,
  the simulation produces a fast counter-Evershed flow (i.e., an inflow
  near τ =1) in some regions within the penumbra, reaching peak flow
  speeds of ∼12 km s<SUP>-1</SUP>. The counter-Evershed flows are
  transient and typically last a few hours before they turn into outflows
  again. By using the kinetic energy equation and evaluating its various
  terms in the simulation box, we found that the Evershed flow occurs
  due to overturning convection in a strongly inclined magnetic field,
  while the counter-Evershed flows can be well-described as siphon flows.

Title: Normal and counter Evershed flows in the photospheric penumbra
    of a sunspot. SPINOR 2D inversions of Hinode-SOT/SP observations
Authors: Siu-Tapia, A.; Lagg, A.; Solanki, S. K.; van Noort, M.;
   Jurčák, J.
Bibcode: 2017A&A...607A..36S
Altcode: 2017arXiv170907386S
  Context. The Evershed effect, a nearly horizontal outflow of material
  seen in the penumbrae of sunspots in the photospheric layers, is a
  common characteristic of well-developed penumbrae, but is still not well
  understood. Even less is known about photospheric horizontal inflows in
  the penumbra, also known as counter Evershed flows. <BR /> Aims: Here we
  present a rare feature observed in the penumbra of the main sunspot of
  AR NOAA 10930. This spot displays the normal Evershed outflow in most
  of the penumbra, but harbors a fast photospheric inflow of material
  over a large sector of the disk-center penumbra. We investigate the
  driving forces of both, the normal and the counter Evershed flows. <BR
  /> Methods: We invert the spectropolarimetric data from Hinode SOT/SP
  using the spatially coupled version of the SPINOR inversion code,
  which allows us to derive height-dependent maps of the relevant
  physical parameters in the sunspot. These maps show considerable fine
  structure. Similarities and differences between the normal Evershed
  outflow and the counter Evershed flow are investigated. <BR /> Results:
  In both the normal and the counter Evershed flows, the material flows
  from regions with field strengths of the order of 1.5-2 kG to regions
  with stronger fields. The sources and sinks of both penumbral flows
  display opposite field polarities, with the sinks (tails of filaments)
  harboring local enhancements in temperature, which are nonetheless
  colder than their sources (heads of filaments). <BR /> Conclusions:
  The anti-correlation of the gradients in the temperature and magnetic
  pressure between the endpoints of the filaments from the two distinct
  penumbral regions is compatible with both the convective driver and
  the siphon flow scenarios. A geometrical scale of the parameters is
  necessary to determine which is the dominant force driving the flows.

Title: Flows along arch filaments observed in the GRIS `very fast
    spectroscopic mode'
Authors: González Manrique, S. J.; Denker, C.; Kuckein, C.; Pastor
   Yabar, A.; Collados, M.; Verma, M.; Balthasar, H.; Diercke, A.;
   Fischer, C. E.; Gömöry, P.; Bello González, N.; Schlichenmaier,
   R.; Cubas Armas, M.; Berkefeld, T.; Feller, A.; Hoch, S.; Hofmann,
   A.; Lagg, A.; Nicklas, H.; Orozco Suárez, D.; Schmidt, D.; Schmidt,
   W.; Sigwarth, M.; Sobotka, M.; Solanki, S. K.; Soltau, D.; Staude,
   J.; Strassmeier, K. G.; Volkmer, R.; von der Lühe, O.; Waldmann, T.
Bibcode: 2017IAUS..327...28G
Altcode: 2017arXiv170102206G
  A new generation of solar instruments provides improved spectral,
  spatial, and temporal resolution, thus facilitating a better
  understanding of dynamic processes on the Sun. High-resolution
  observations often reveal multiple-component spectral line profiles,
  e.g., in the near-infrared He i 10830 Å triplet, which provides
  information about the chromospheric velocity and magnetic fine
  structure. We observed an emerging flux region, including two small
  pores and an arch filament system, on 2015 April 17 with the `very
  fast spectroscopic mode' of the GREGOR Infrared Spectrograph (GRIS)
  situated at the 1.5-meter GREGOR solar telescope at Observatorio del
  Teide, Tenerife, Spain. We discuss this method of obtaining fast (one
  per minute) spectral scans of the solar surface and its potential to
  follow dynamic processes on the Sun. We demonstrate the performance
  of the `very fast spectroscopic mode' by tracking chromospheric
  high-velocity features in the arch filament system.

Title: Measurements of Photospheric and Chromospheric Magnetic Fields
Authors: Lagg, Andreas; Lites, Bruce; Harvey, Jack; Gosain, Sanjay;
   Centeno, Rebecca
Bibcode: 2017SSRv..210...37L
Altcode: 2015arXiv151006865L; 2015SSRv..tmp..115L
  The Sun is replete with magnetic fields, with sunspots, pores
  and plage regions being their most prominent representatives on
  the solar surface. But even far away from these active regions,
  magnetic fields are ubiquitous. To a large extent, their importance
  for the thermodynamics in the solar photosphere is determined by the
  total magnetic flux. Whereas in low-flux quiet Sun regions, magnetic
  structures are shuffled around by the motion of granules, the high-flux
  areas like sunspots or pores effectively suppress convection, leading
  to a temperature decrease of up to 3000 K. The importance of magnetic
  fields to the conditions in higher atmospheric layers, the chromosphere
  and corona, is indisputable. Magnetic fields in both active and
  quiet regions are the main coupling agent between the outer layers
  of the solar atmosphere, and are therefore not only involved in the
  structuring of these layers, but also for the transport of energy from
  the solar surface through the corona to the interplanetary space. <P
  />Consequently, inference of magnetic fields in the photosphere, and
  especially in the chromosphere, is crucial to deepen our understanding
  not only for solar phenomena such as chromospheric and coronal
  heating, flares or coronal mass ejections, but also for fundamental
  physical topics like dynamo theory or atomic physics. In this review,
  we present an overview of significant advances during the last decades
  in measurement techniques, analysis methods, and the availability of
  observatories, together with some selected results. We discuss the
  problems of determining magnetic fields at smallest spatial scales,
  connected with increasing demands on polarimetric sensitivity and
  temporal resolution, and highlight some promising future developments
  for their solution.

Title: Three-dimensional magnetic structure of a sunspot: Comparison
    of the photosphere and upper chromosphere
Authors: Joshi, Jayant; Lagg, Andreas; Hirzberger, Johann; Solanki,
   Sami K.
Bibcode: 2017A&A...604A..98J
Altcode: 2017arXiv170508404J
  <BR /> Aims: We investigate the magnetic field of a sunspot in the
  upper chromosphere and compare it to the photospheric properties
  of the field. <BR /> Methods: We observed the main leading sunspot
  of the active region NOAA 11124 during two days with the Tenerife
  Infrared Polarimeter-2 (TIP-2) mounted at the German Vacuum Tower
  Telescope (VTT). Through inversion of Stokes spectra of the He I
  triplet at 10 830 Å, we obtained the magnetic field vector of the
  upper chromosphere. For comparison with the photosphere, we applied
  height-dependent inversions of the Si I 10 827.1 Å and Ca I 10 833.4 Å
  lines. <BR /> Results: We found that the umbral magnetic field strength
  in the upper chromosphere is lower by a factor of 1.30-1.65 compared
  to the photosphere. The magnetic field strength of the umbra decreases
  from the photosphere toward the upper chromosphere by an average rate of
  0.5-0.9 G km<SUP>-1</SUP>. The difference in the magnetic field strength
  between both atmospheric layers steadily decreases from the sunspot
  center to the outer boundary of the sunspot; the field, in particular
  its horizontal component, is stronger in the chromopshere outside the
  spot and this is suggestive of a magnetic canopy. The sunspot displays
  a twist that on average is similar in the two layers. However, the
  differential twist between the photosphere and chromosphere increases
  rapidly toward the outer penumbral boundary. The magnetic field
  vector is more horizontal with respect to the solar surface by roughly
  5-20° in the photosphere compared to the upper chromosphere. Above
  a lightbridge, the chromospheric magnetic field is equally strong as
  that in the umbra, whereas the field of the lightbridge is weaker than
  its surroundings in the photosphere by roughly 1 kG. This suggests a
  cusp-like magnetic field structure above the lightbridge.

Title: Extended Subadiabatic Layer in Simulations of Overshooting
    Convection
Authors: Käpylä, Petri J.; Rheinhardt, Matthias; Brandenburg, Axel;
   Arlt, Rainer; Käpylä, Maarit J.; Lagg, Andreas; Olspert, Nigul;
   Warnecke, Jörn
Bibcode: 2017ApJ...845L..23K
Altcode: 2017arXiv170306845K
  We present numerical simulations of hydrodynamic overshooting convection
  in local Cartesian domains. We find that a substantial fraction
  of the lower part of the convection zone (CZ) is stably stratified
  according to the Schwarzschild criterion while the enthalpy flux is
  outward directed. This occurs when the heat conduction profile at the
  bottom of the CZ is smoothly varying, based either on a Kramers-like
  opacity prescription as a function of temperature and density or a
  static profile of a similar shape. We show that the subadiabatic layer
  arises due to nonlocal energy transport by buoyantly driven downflows
  in the upper parts of the CZ. Analysis of the force balance of the
  upflows and downflows confirms that convection is driven by cooling
  at the surface. We find that the commonly used prescription for the
  convective enthalpy flux being proportional to the negative entropy
  gradient does not hold in the stably stratified layers where the flux is
  positive. We demonstrate the existence of a non-gradient contribution
  to the enthalpy flux, which is estimated to be important throughout
  the convective layer. A quantitative analysis of downflows indicates
  a transition from a tree-like structure where smaller downdrafts merge
  into larger ones in the upper parts to a structure in the deeper parts
  where a height-independent number of strong downdrafts persist. This
  change of flow topology occurs when a substantial subadiabatic layer
  is present in the lower part of the CZ.

Title: Erratum: Morphological Properties of
    Slender CaII H Fibrils Observed by sunrise II (<A
href="http://doi.org/10.3847/1538-4365/229/1/6">ApJS 229, 1, 6</A>)
Authors: Gafeira, R.; Lagg, A.; Solanki, S. K.; Jafarzadeh, S.;
   van Noort, M.; Barthol, P.; Blanco Rodríguez, J.; del Toro Iniesta,
   J. C.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Knölker, M.; Orozco
   Suárez, D.; Riethmüller, T. L.; Schmidt, W.
Bibcode: 2017ApJS..230...11G
Altcode:
  No abstract at ADS

Title: The Second Flight of the Sunrise Balloon-borne Solar
Observatory: Overview of Instrument Updates, the Flight, the Data,
    and First Results
Authors: Solanki, S. K.; Riethmüller, T. L.; Barthol, P.; Danilovic,
   S.; Deutsch, W.; Doerr, H. -P.; Feller, A.; Gandorfer, A.; Germerott,
   D.; Gizon, L.; Grauf, B.; Heerlein, K.; Hirzberger, J.; Kolleck, M.;
   Lagg, A.; Meller, R.; Tomasch, G.; van Noort, M.; Blanco Rodríguez,
   J.; Gasent Blesa, J. L.; Balaguer Jiménez, M.; Del Toro Iniesta,
   J. C.; López Jiménez, A. C.; Orozco Suarez, D.; Berkefeld, T.;
   Halbgewachs, C.; Schmidt, W.; Álvarez-Herrero, A.; Sabau-Graziati,
   L.; Pérez Grande, I.; Martínez Pillet, V.; Card, G.; Centeno, R.;
   Knölker, M.; Lecinski, A.
Bibcode: 2017ApJS..229....2S
Altcode: 2017arXiv170101555S
  The Sunrise balloon-borne solar observatory, consisting of a 1 m
  aperture telescope that provides a stabilized image to a UV filter
  imager and an imaging vector polarimeter, carried out its second science
  flight in 2013 June. It provided observations of parts of active regions
  at high spatial resolution, including the first high-resolution images
  in the Mg II k line. The obtained data are of very high quality, with
  the best UV images reaching the diffraction limit of the telescope
  at 3000 Å after Multi-Frame Blind Deconvolution reconstruction
  accounting for phase-diversity information. Here a brief update is
  given of the instruments and the data reduction techniques, which
  includes an inversion of the polarimetric data. Mainly those aspects
  that evolved compared with the first flight are described. A tabular
  overview of the observations is given. In addition, an example time
  series of a part of the emerging active region NOAA AR 11768 observed
  relatively close to disk center is described and discussed in some
  detail. The observations cover the pores in the trailing polarity of
  the active region, as well as the polarity inversion line where flux
  emergence was ongoing and a small flare-like brightening occurred in
  the course of the time series. The pores are found to contain magnetic
  field strengths ranging up to 2500 G, and while large pores are clearly
  darker and cooler than the quiet Sun in all layers of the photosphere,
  the temperature and brightness of small pores approach or even exceed
  those of the quiet Sun in the upper photosphere.

Title: Vertical magnetic field gradient in the photospheric layers
    of sunspots
Authors: Joshi, Jayant; Lagg, Andreas; Hirzberger, Johann; Solanki,
   Sami K.; Tiwari, Sanjiv K.
Bibcode: 2017A&A...599A..35J
Altcode: 2016arXiv161000500J
  <BR /> Aims: We investigate the vertical gradient of the magnetic
  field of sunspots in the photospheric layer. <BR /> Methods:
  Independent observations were obtained with the Solar Optical
  Telescope/Spectropolarimeter (SOT/SP) on board the Hinode spacecraft and
  with the Tenrife Infrared Polarimeter-2 (TIP-2) mounted at the German
  Vacuum Tower Telescope (VTT). We apply state-of-the-art inversion
  techniques to both data sets to retrieve the magnetic field and the
  corresponding vertical gradient along with other atmospheric parameters
  in the solar photosphere. <BR /> Results: In the sunspot penumbrae we
  detected patches of negative vertical gradients of the magnetic field
  strength, I.e., the magnetic field strength decreases with optical depth
  in the photosphere. The negative gradient patches are located in the
  inner and partly in the middle penumbrae in both data sets. From the
  SOT/SP observations we found that the negative gradient patches are
  restricted mainly to the deep photospheric layers and are concentrated
  near the edges of the penumbral filaments. Magnetohydrodynamic (MHD)
  simulations also show negative gradients in the inner penumbrae, also
  at the locations of filaments. In the observations and the simulation
  negative gradients of the magnetic field vs. optical depth dominate
  at some radial distances in the penumbra. The negative gradient with
  respect to optical depth in the inner penumbrae persists even after
  averaging in the azimuthal direction in the observations and, to a
  lesser extent, in the MHD simulations. If the gradients in the MHD
  simulations are determined with respect to geometrical height, then
  the azimuthal averages are always positive within the sunspot (above
  log τ = 0), corresponding to magnetic field increasing with depth,
  as generally expected. <BR /> Conclusions: We interpret the observed
  localized presence of negative vertical gradient of the magnetic
  field strength in the observations as a consequence of stronger field
  from spines expanding with height and closing above the weaker field
  inter-spines. The presence of the negative gradients with respect
  to optical depth after azimuthal averaging can be explained by two
  different mechanisms: the high corrugation of equal optical depth
  surfaces and the cancellation of polarized signal due to the presence
  of unresolved opposite polarity patches in the deeper layers of the
  penumbra.

Title: Morphological Properties of Slender Ca II H Fibrils Observed
    by SUNRISE II
Authors: Gafeira, R.; Lagg, A.; Solanki, S. K.; Jafarzadeh, S.;
   van Noort, M.; Barthol, P.; Blanco Rodríguez, J.; del Toro Iniesta,
   J. C.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Knölker, M.; Orozco
   Suárez, D.; Riethmüller, T. L.; Schmidt, W.
Bibcode: 2017ApJS..229....6G
Altcode: 2016arXiv161200319G
  We use seeing-free high spatial resolution Ca II H data obtained by
  the SUNRISE observatory to determine properties of slender fibrils
  in the lower solar chromosphere. In this work we use intensity images
  taken with the SuFI instrument in the Ca II H line during the second
  scientific flight of the SUNRISE observatory to identify and track
  elongated bright structures. After identification, we analyze theses
  structures to extract their morphological properties. We identify
  598 slender Ca II H fibrils (SCFs) with an average width of around
  180 km, length between 500 and 4000 km, average lifetime of ≈400
  s, and average curvature of 0.002 arcsec<SUP>-1</SUP>. The maximum
  lifetime of the SCFs within our time series of 57 minutes is ≈2000
  s. We discuss similarities and differences of the SCFs with other
  small-scale, chromospheric structures such as spicules of type I and
  II, or Ca II K fibrils.

Title: Oscillations on Width and Intensity of Slender Ca II H Fibrils
    from Sunrise/SuFI
Authors: Gafeira, R.; Jafarzadeh, S.; Solanki, S. K.; Lagg, A.;
   van Noort, M.; Barthol, P.; Blanco Rodríguez, J.; del Toro Iniesta,
   J. C.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Knölker, M.; Orozco
   Suárez, D.; Riethmüller, T. L.; Schmidt, W.
Bibcode: 2017ApJS..229....7G
Altcode: 2017arXiv170102801G
  We report the detection of oscillations in slender Ca II H fibrils
  (SCFs) from high-resolution observations acquired with the Sunrise
  balloon-borne solar observatory. The SCFs show obvious oscillations in
  their intensity, but also their width. The oscillatory behaviors are
  investigated at several positions along the axes of the SCFs. A large
  majority of fibrils show signs of oscillations in intensity. Their
  periods and phase speeds are analyzed using a wavelet analysis. The
  width and intensity perturbations have overlapping distributions
  of the wave period. The obtained distributions have median values
  of the period of 32 ± 17 s and 36 ± 25 s, respectively. We
  find that the fluctuations of both parameters propagate in
  the SCFs with speeds of {11}<SUB>-11</SUB><SUP>+49</SUP> km
  s<SUP>-1</SUP> and {15}<SUB>-15</SUB><SUP>+34</SUP> km s<SUP>-1</SUP>,
  respectively. Furthermore, the width and intensity oscillations have a
  strong tendency to be either in anti-phase or, to a smaller extent, in
  phase. This suggests that the oscillations of both parameters are caused
  by the same wave mode and that the waves are likely propagating. Taking
  all the evidence together, the most likely wave mode to explain all
  measurements and criteria is the fast sausage mode.

Title: Moving Magnetic Features around a Pore
Authors: Kaithakkal, A. J.; Riethmüller, T. L.; Solanki, S. K.; Lagg,
   A.; Barthol, P.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; vanNoort,
   M.; Blanco Rodríguez, J.; Del Toro Iniesta, J. C.; Orozco Suárez,
   D.; Schmidt, W.; Martínez Pillet, V.; Knölker, M.
Bibcode: 2017ApJS..229...13K
Altcode: 2016arXiv160905664K
  Spectropolarimetric observations from Sunrise/IMaX, obtained in 2013
  June, are used for a statistical analysis to determine the physical
  properties of moving magnetic features (MMFs) observed near a pore. MMFs
  of the same and opposite polarity, with respect to the pore, are found
  to stream from its border at an average speed of 1.3 km s<SUP>-1</SUP>
  and 1.2 km s<SUP>-1</SUP>, respectively, with mainly same-polarity MMFs
  found further away from the pore. MMFs of both polarities are found to
  harbor rather weak, inclined magnetic fields. Opposite-polarity MMFs
  are blueshifted, whereas same-polarity MMFs do not show any preference
  for up- or downflows. Most of the MMFs are found to be of sub-arcsecond
  size and carry a mean flux of ∼1.2 × 10<SUP>17</SUP> Mx.

Title: Measurements of photospheric magnetic fields
Authors: Lagg, Andreas
Bibcode: 2017psio.confE..31L
Altcode:
  No abstract at ADS

Title: Slipping reconnection in a solar flare observed in high
    resolution with the GREGOR solar telescope
Authors: Sobotka, M.; Dudík, J.; Denker, C.; Balthasar, H.; Jurčák,
   J.; Liu, W.; Berkefeld, T.; Collados Vera, M.; Feller, A.; Hofmann,
   A.; Kneer, F.; Kuckein, C.; Lagg, A.; Louis, R. E.; von der Lühe, O.;
   Nicklas, H.; Schlichenmaier, R.; Schmidt, D.; Schmidt, W.; Sigwarth,
   M.; Solanki, S. K.; Soltau, D.; Staude, J.; Strassmeier, K. G.;
   Volkmer, R.; Waldmann, T.
Bibcode: 2016A&A...596A...1S
Altcode: 2016arXiv160500464S
  A small flare ribbon above a sunspot umbra in active region 12205 was
  observed on November 7, 2014, at 12:00 UT in the blue imaging channel
  of the 1.5 m GREGOR telescope, using a 1 Å Ca II H interference
  filter. Context observations from the Atmospheric Imaging Assembly
  (AIA) onboard the Solar Dynamics Observatory (SDO), the Solar Optical
  Telescope (SOT) onboard Hinode, and the Interface Region Imaging
  Spectrograph (IRIS) show that this ribbon is part of a larger one
  that extends through the neighboring positive polarities and also
  participates in several other flares within the active region. We
  reconstructed a time series of 140 s of Ca II H images by means of the
  multiframe blind deconvolution method, which resulted in spatial and
  temporal resolutions of 0.1″ and 1 s. Light curves and horizontal
  velocities of small-scale bright knots in the observed flare ribbon
  were measured. Some knots are stationary, but three move along the
  ribbon with speeds of 7-11 km s<SUP>-1</SUP>. Two of them move in the
  opposite direction and exhibit highly correlated intensity changes,
  which provides evidence of a slipping reconnection at small spatial
  scales. <P />Movies associated to Figs. 1 and 2 are available at <A
  href="http://www.aanda.org/10.1051/0004-6361/201527966/olm">http://www.aanda.org</A>

Title: Deep probing of the photospheric sunspot penumbra: no evidence
    of field-free gaps
Authors: Borrero, J. M.; Asensio Ramos, A.; Collados, M.;
   Schlichenmaier, R.; Balthasar, H.; Franz, M.; Rezaei, R.; Kiess, C.;
   Orozco Suárez, D.; Pastor Yabar, A.; Berkefeld, T.; von der Lühe,
   O.; Schmidt, D.; Schmidt, W.; Sigwarth, M.; Soltau, D.; Volkmer, R.;
   Waldmann, T.; Denker, C.; Hofmann, A.; Staude, J.; Strassmeier, K. G.;
   Feller, A.; Lagg, A.; Solanki, S. K.; Sobotka, M.; Nicklas, H.
Bibcode: 2016A&A...596A...2B
Altcode: 2016arXiv160708165B
  Context. Some models for the topology of the magnetic field in
  sunspot penumbrae predict regions free of magnetic fields or with
  only dynamically weak fields in the deep photosphere. <BR /> Aims:
  We aim to confirm or refute the existence of weak-field regions in
  the deepest photospheric layers of the penumbra. <BR /> Methods:
  We investigated the magnetic field at log τ<SUB>5</SUB> = 0 is
  by inverting spectropolarimetric data of two different sunspots
  located very close to disk center with a spatial resolution of
  approximately 0.4-0.45''. The data have been recorded using the GRIS
  instrument attached to the 1.5-m solar telescope GREGOR at the El
  Teide observatory. The data include three Fe I lines around 1565 nm,
  whose sensitivity to the magnetic field peaks half a pressure scale
  height deeper than the sensitivity of the widely used Fe I spectral
  line pair at 630 nm. Before the inversion, the data were corrected
  for the effects of scattered light using a deconvolution method with
  several point spread functions. <BR /> Results: At log τ<SUB>5</SUB>
  = 0 we find no evidence of regions with dynamically weak (B&lt;
  500 Gauss) magnetic fields in sunspot penumbrae. This result is much
  more reliable than previous investigations made on Fe I lines at 630
  nm. Moreover, the result is independent of the number of nodes employed
  in the inversion, is independent of the point spread function used to
  deconvolve the data, and does not depend on the amount of stray light
  (I.e., wide-angle scattered light) considered.

Title: Spectropolarimetric observations of an arch filament system
    with the GREGOR solar telescope
Authors: Balthasar, H.; Gömöry, P.; González Manrique, S. J.;
   Kuckein, C.; Kavka, J.; Kučera, A.; Schwartz, P.; Vašková, R.;
   Berkefeld, T.; Collados Vera, M.; Denker, C.; Feller, A.; Hofmann,
   A.; Lagg, A.; Nicklas, H.; Orozco Suárez, D.; Pastor Yabar, A.;
   Rezaei, R.; Schlichenmaier, R.; Schmidt, D.; Schmidt, W.; Sigwarth,
   M.; Sobotka, M.; Solanki, S. K.; Soltau, D.; Staude, J.; Strassmeier,
   K. G.; Volkmer, R.; von der Lühe, O.; Waldmann, T.
Bibcode: 2016AN....337.1050B
Altcode: 2016arXiv160901514B
  Arch filament systems occur in active sunspot groups, where a fibril
  structure connects areas of opposite magnetic polarity, in contrast to
  active region filaments that follow the polarity inversion line. We
  used the GREGOR Infrared Spectrograph (GRIS) to obtain the full
  Stokes vector in the spectral lines Si I λ1082.7 nm, He I λ1083.0
  nm, and Ca I λ1083.9 nm. We focus on the near-infrared calcium line
  to investigate the photospheric magnetic field and velocities, and
  use the line core intensities and velocities of the helium line to
  study the chromospheric plasma. The individual fibrils of the arch
  filament system connect the sunspot with patches of magnetic polarity
  opposite to that of the spot. These patches do not necessarily coincide
  with pores, where the magnetic field is strongest. Instead, areas are
  preferred not far from the polarity inversion line. These areas exhibit
  photospheric downflows of moderate velocity, but significantly higher
  downflows of up to 30 km s<SUP>-1</SUP> in the chromospheric helium
  line. Our findings can be explained with new emerging flux where the
  matter flows downward along the field lines of rising flux tubes,
  in agreement with earlier results.

Title: Magnetic fields of opposite polarity in sunspot penumbrae
Authors: Franz, M.; Collados, M.; Bethge, C.; Schlichenmaier, R.;
   Borrero, J. M.; Schmidt, W.; Lagg, A.; Solanki, S. K.; Berkefeld,
   T.; Kiess, C.; Rezaei, R.; Schmidt, D.; Sigwarth, M.; Soltau, D.;
   Volkmer, R.; von der Luhe, O.; Waldmann, T.; Orozco, D.; Pastor Yabar,
   A.; Denker, C.; Balthasar, H.; Staude, J.; Hofmann, A.; Strassmeier,
   K.; Feller, A.; Nicklas, H.; Kneer, F.; Sobotka, M.
Bibcode: 2016A&A...596A...4F
Altcode: 2016arXiv160800513F
  Context. A significant part of the penumbral magnetic field returns
  below the surface in the very deep photosphere. For lines in the
  visible, a large portion of this return field can only be detected
  indirectly by studying its imprints on strongly asymmetric and
  three-lobed Stokes V profiles. Infrared lines probe a narrow layer
  in the very deep photosphere, providing the possibility of directly
  measuring the orientation of magnetic fields close to the solar
  surface. <BR /> Aims: We study the topology of the penumbral magnetic
  field in the lower photosphere, focusing on regions where it returns
  below the surface. <BR /> Methods: We analyzed 71 spectropolarimetric
  datasets from Hinode and from the GREGOR infrared spectrograph. We
  inferred the quality and polarimetric accuracy of the infrared data
  after applying several reduction steps. Techniques of spectral
  inversion and forward synthesis were used to test the detection
  algorithm. We compared the morphology and the fractional penumbral
  area covered by reversed-polarity and three-lobed Stokes V profiles for
  sunspots at disk center. We determined the amount of reversed-polarity
  and three-lobed Stokes V profiles in visible and infrared data of
  sunspots at various heliocentric angles. From the results, we computed
  center-to-limb variation curves, which were interpreted in the context
  of existing penumbral models. <BR /> Results: Observations in visible
  and near-infrared spectral lines yield a significant difference in the
  penumbral area covered by magnetic fields of opposite polarity. In
  the infrared, the number of reversed-polarity Stokes V profiles is
  smaller by a factor of two than in the visible. For three-lobed Stokes
  V profiles the numbers differ by up to an order of magnitude.

Title: Horizontal flow fields in and around a small active region. The
    transition period between flux emergence and decay
Authors: Verma, M.; Denker, C.; Balthasar, H.; Kuckein, C.; González
   Manrique, S. J.; Sobotka, M.; Bello González, N.; Hoch, S.; Diercke,
   A.; Kummerow, P.; Berkefeld, T.; Collados, M.; Feller, A.; Hofmann,
   A.; Kneer, F.; Lagg, A.; Löhner-Böttcher, J.; Nicklas, H.; Pastor
   Yabar, A.; Schlichenmaier, R.; Schmidt, D.; Schmidt, W.; Schubert,
   M.; Sigwarth, M.; Solanki, S. K.; Soltau, D.; Staude, J.; Strassmeier,
   K. G.; Volkmer, R.; von der Lühe, O.; Waldmann, T.
Bibcode: 2016A&A...596A...3V
Altcode: 2016arXiv160507462V
  Context. The solar magnetic field is responsible for all aspects
  of solar activity. Thus, emergence of magnetic flux at the surface
  is the first manifestation of the ensuing solar activity. <BR />
  Aims: Combining high-resolution and synoptic observations aims to
  provide a comprehensive description of flux emergence at photospheric
  level and of the growth process that eventually leads to a mature
  active region. <BR /> Methods: The small active region NOAA 12118
  emerged on 2014 July 17 and was observed one day later with the 1.5-m
  GREGOR solar telescope on 2014 July 18. High-resolution time-series
  of blue continuum and G-band images acquired in the blue imaging
  channel (BIC) of the GREGOR Fabry-Pérot Interferometer (GFPI) were
  complemented by synoptic line-of-sight magnetograms and continuum
  images obtained with the Helioseismic and Magnetic Imager (HMI) onboard
  the Solar Dynamics Observatory (SDO). Horizontal proper motions and
  horizontal plasma velocities were computed with local correlation
  tracking (LCT) and the differential affine velocity estimator (DAVE),
  respectively. Morphological image processing was employed to measure
  the photometric and magnetic area, magnetic flux, and the separation
  profile of the emerging flux region during its evolution. <BR />
  Results: The computed growth rates for photometric area, magnetic
  area, and magnetic flux are about twice as high as the respective
  decay rates. The space-time diagram using HMI magnetograms of five days
  provides a comprehensive view of growth and decay. It traces a leaf-like
  structure, which is determined by the initial separation of the two
  polarities, a rapid expansion phase, a time when the spread stalls,
  and a period when the region slowly shrinks again. The separation
  rate of 0.26 km s<SUP>-1</SUP> is highest in the initial stage, and
  it decreases when the separation comes to a halt. Horizontal plasma
  velocities computed at four evolutionary stages indicate a changing
  pattern of inflows. In LCT maps we find persistent flow patterns such
  as outward motions in the outer part of the two major pores, a diverging
  feature near the trailing pore marking the site of upwelling plasma and
  flux emergence, and low velocities in the interior of dark pores. We
  detected many elongated rapidly expanding granules between the two
  major polarities, with dimensions twice as large as the normal granules.

Title: Upper chromospheric magnetic field of a sunspot penumbra:
    observations of fine structure
Authors: Joshi, J.; Lagg, A.; Solanki, S. K.; Feller, A.; Collados,
   M.; Orozco Suárez, D.; Schlichenmaier, R.; Franz, M.; Balthasar,
   H.; Denker, C.; Berkefeld, T.; Hofmann, A.; Kiess, C.; Nicklas, H.;
   Pastor Yabar, A.; Rezaei, R.; Schmidt, D.; Schmidt, W.; Sobotka, M.;
   Soltau, D.; Staude, J.; Strassmeier, K. G.; Volkmer, R.; von der Lühe,
   O.; Waldmann, T.
Bibcode: 2016A&A...596A...8J
Altcode: 2016arXiv160801988J
  <BR /> Aims: The fine-structure of the magnetic field in a sunspot
  penumbra in the upper chromosphere is to be explored and compared
  to that in the photosphere. <BR /> Methods: Spectropolarimetric
  observations with high spatial resolution were recorded with the 1.5-m
  GREGOR telescope using the GREGOR Infrared Spectrograph (GRIS). The
  observed spectral domain includes the upper chromospheric Hei triplet
  at 10 830 Å and the photospheric Sii 10 827.1 Å and Cai 10 833.4 Å
  spectral lines. The upper chromospheric magnetic field is obtained
  by inverting the Hei triplet assuming a Milne-Eddington-type model
  atmosphere. A height-dependent inversion was applied to the Sii 10
  827.1 Å and Cai 10 833.4 Å lines to obtain the photospheric magnetic
  field. <BR /> Results: We find that the inclination of the magnetic
  field varies in the azimuthal direction in the photosphere and in the
  upper chromosphere. The chromospheric variations coincide remarkably
  well with the variations in the inclination of the photospheric field
  and resemble the well-known spine and interspine structure in the
  photospheric layers of penumbrae. The typical peak-to-peak variations
  in the inclination of the magnetic field in the upper chromosphere
  are found to be 10°-15°, which is roughly half the variation in
  the photosphere. In contrast, the magnetic field strength of the
  observed penumbra does not vary on small spatial scales in the upper
  chromosphere. <BR /> Conclusions: Thanks to the high spatial resolution
  of the observations that is possible with the GREGOR telescope at 1.08
  microns, we find that the prominent small-scale fluctuations in the
  magnetic field inclination, which are a salient part of the property
  of sunspot penumbral photospheres, also persist in the chromosphere,
  although at somewhat reduced amplitudes. Such a complex magnetic
  configuration may facilitate penumbral chromospheric dynamic phenomena,
  such as penumbral micro-jets or transient bright dots.

Title: Active region fine structure observed at 0.08 arcsec resolution
Authors: Schlichenmaier, R.; von der Lühe, O.; Hoch, S.; Soltau, D.;
   Berkefeld, T.; Schmidt, D.; Schmidt, W.; Denker, C.; Balthasar, H.;
   Hofmann, A.; Strassmeier, K. G.; Staude, J.; Feller, A.; Lagg, A.;
   Solanki, S. K.; Collados, M.; Sigwarth, M.; Volkmer, R.; Waldmann,
   T.; Kneer, F.; Nicklas, H.; Sobotka, M.
Bibcode: 2016A&A...596A...7S
Altcode: 2016arXiv160707094S
  Context. The various mechanisms of magneto-convective energy transport
  determine the structure of sunspots and active regions. <BR />
  Aims: We characterise the appearance of light bridges and other
  fine-structure details and elaborate on their magneto-convective
  nature. <BR /> Methods: We present speckle-reconstructed images taken
  with the broad-band imager (BBI) at the 1.5 m GREGOR telescope in the
  486 nm and 589 nm bands. We estimate the spatial resolution from the
  noise characteristics of the image bursts and obtain 0.08″ at 589
  nm. We describe structure details in individual best images as well
  as the temporal evolution of selected features. <BR /> Results: We
  find branched dark lanes extending along thin (≈1″) light bridges
  in sunspots at various heliocentric angles. In thick (≳ 2″) light
  bridges the branches are disconnected from the central lane and have a Y
  shape with a bright grain toward the umbra. The images reveal that light
  bridges exist on varying intensity levels and that their small-scale
  features evolve on timescales of minutes. Faint light bridges show
  dark lanes outlined by the surrounding bright features. Dark lanes are
  very common and are also found in the boundary of pores. They have a
  characteristic width of 0.1″ or smaller. Intergranular dark lanes of
  that width are seen in active region granulation. <BR /> Conclusions: We
  interpret our images in the context of magneto-convective simulations
  and findings: while central dark lanes in thin light bridges are
  elevated and associated with a density increase above upflows, the dark
  lane branches correspond to locations of downflows and are depressed
  relative to the adjacent bright plasma. Thick light bridges with central
  dark lanes show no projection effect. They have a flat elevated plateau
  that falls off steeply at the umbral boundary. There, Y-shaped filaments
  form as they do in the inner penumbra. This indicates the presence of
  inclined magnetic fields, meaning that the umbral magnetic field is
  wrapped around the convective light bridge.

Title: Probing deep photospheric layers of the quiet Sun with high
    magnetic sensitivity
Authors: Lagg, A.; Solanki, S. K.; Doerr, H. -P.; Martínez González,
   M. J.; Riethmüller, T.; Collados Vera, M.; Schlichenmaier, R.;
   Orozco Suárez, D.; Franz, M.; Feller, A.; Kuckein, C.; Schmidt, W.;
   Asensio Ramos, A.; Pastor Yabar, A.; von der Lühe, O.; Denker, C.;
   Balthasar, H.; Volkmer, R.; Staude, J.; Hofmann, A.; Strassmeier,
   K.; Kneer, F.; Waldmann, T.; Borrero, J. M.; Sobotka, M.; Verma, M.;
   Louis, R. E.; Rezaei, R.; Soltau, D.; Berkefeld, T.; Sigwarth, M.;
   Schmidt, D.; Kiess, C.; Nicklas, H.
Bibcode: 2016A&A...596A...6L
Altcode: 2016arXiv160506324L
  Context. Investigations of the magnetism of the quiet Sun are hindered
  by extremely weak polarization signals in Fraunhofer spectral
  lines. Photon noise, straylight, and the systematically different
  sensitivity of the Zeeman effect to longitudinal and transversal
  magnetic fields result in controversial results in terms of the strength
  and angular distribution of the magnetic field vector. <BR /> Aims:
  The information content of Stokes measurements close to the diffraction
  limit of the 1.5 m GREGOR telescope is analyzed. We took the effects of
  spatial straylight and photon noise into account. <BR /> Methods: Highly
  sensitive full Stokes measurements of a quiet-Sun region at disk center
  in the deep photospheric Fe I lines in the 1.56 μm region were obtained
  with the infrared spectropolarimeter GRIS at the GREGOR telescope. Noise
  statistics and Stokes V asymmetries were analyzed and compared to a
  similar data set of the Hinode spectropolarimeter (SOT/SP). Simple
  diagnostics based directly on the shape and strength of the profiles
  were applied to the GRIS data. We made use of the magnetic line ratio
  technique, which was tested against realistic magneto-hydrodynamic
  simulations (MURaM). <BR /> Results: About 80% of the GRIS spectra
  of a very quiet solar region show polarimetric signals above a 3σ
  level. Area and amplitude asymmetries agree well with small-scale
  surface dynamo-magneto hydrodynamic simulations. The magnetic line ratio
  analysis reveals ubiquitous magnetic regions in the ten to hundred Gauss
  range with some concentrations of kilo-Gauss fields. <BR /> Conclusions:
  The GRIS spectropolarimetric data at a spatial resolution of ≈0.̋4
  are so far unique in the combination of high spatial resolution scans
  and high magnetic field sensitivity. Nevertheless, the unavoidable
  effect of spatial straylight and the resulting dilution of the weak
  Stokes profiles means that inversion techniques still bear a high risk
  of misinterpretating the data.

Title: Flow and magnetic field properties in the trailing sunspots
    of active region NOAA 12396
Authors: Verma, M.; Denker, C.; Böhm, F.; Balthasar, H.; Fischer,
   C. E.; Kuckein, C.; Bello González, N.; Berkefeld, T.; Collados,
   M.; Diercke, A.; Feller, A.; González Manrique, S. J.; Hofmann, A.;
   Lagg, A.; Nicklas, H.; Orozco Suárez, D.; Pator Yabar, A.; Rezaei,
   R.; Schlichenmaier, R.; Schmidt, D.; Schmidt, W.; Sigwarth, M.;
   Sobotka, M.; Solanki, S. K.; Soltau, D.; Staude, J.; Strassmeier,
   K. G.; Volkmer, R.; von der Lühe, O.; Waldmann, T.
Bibcode: 2016AN....337.1090V
Altcode:
  Improved measurements of the photospheric and chromospheric
  three-dimensional magnetic and flow fields are crucial for a precise
  determination of the origin and evolution of active regions. We present
  an illustrative sample of multi-instrument data acquired during a
  two-week coordinated observing campaign in August 2015 involving,
  among others, the GREGOR solar telescope (imaging and near-infrared
  spectroscopy) and the space missions Solar Dynamics Observatory (SDO)
  and Interface Region Imaging Spectrograph (IRIS). The observations
  focused on the trailing part of active region NOAA 12396 with complex
  polarity inversion lines and strong intrusions of opposite polarity
  flux. The GREGOR Infrared Spectrograph (GRIS) provided Stokes IQUV
  spectral profiles in the photospheric Si I λ1082.7 nm line, the
  chromospheric He I λ1083.0 nm triplet, and the photospheric Ca I
  λ1083.9 nm line. Carefully calibrated GRIS scans of the active region
  provided maps of Doppler velocity and magnetic field at different
  atmospheric heights. We compare quick-look maps with those obtained
  with the ``Stokes Inversions based on Response functions'' (SIR)
  code, which furnishes deeper insight into the magnetic properties
  of the region. We find supporting evidence that newly emerging flux
  and intruding opposite polarity flux are hampering the formation
  of penumbrae, i.e., a penumbra fully surrounding a sunspot is only
  expected after cessation of flux emergence in proximity to the sunspots.

Title: Three-dimensional structure of a sunspot light bridge
Authors: Felipe, T.; Collados, M.; Khomenko, E.; Kuckein, C.; Asensio
   Ramos, A.; Balthasar, H.; Berkefeld, T.; Denker, C.; Feller, A.;
   Franz, M.; Hofmann, A.; Joshi, J.; Kiess, C.; Lagg, A.; Nicklas, H.;
   Orozco Suárez, D.; Pastor Yabar, A.; Rezaei, R.; Schlichenmaier,
   R.; Schmidt, D.; Schmidt, W.; Sigwarth, M.; Sobotka, M.; Solanki,
   S. K.; Soltau, D.; Staude, J.; Strassmeier, K. G.; Volkmer, R.;
   von der Lühe, O.; Waldmann, T.
Bibcode: 2016A&A...596A..59F
Altcode: 2016arXiv161104803F
  Context. Active regions are the most prominent manifestations of solar
  magnetic fields; their generation and dissipation are fundamental
  problems in solar physics. Light bridges are commonly present during
  sunspot decay, but a comprehensive picture of their role in the
  removal of the photospheric magnetic field is still lacking. <BR />
  Aims: We study the three-dimensional configuration of a sunspot,
  and in particular, its light bridge, during one of the last stages of
  its decay. <BR /> Methods: We present the magnetic and thermodynamical
  stratification inferred from full Stokes inversions of the photospheric
  Si I 10 827 Å and Ca I 10 839 Å lines obtained with the GREGOR
  Infrared Spectrograph of the GREGOR telescope at the Observatorio del
  Teide, Tenerife, Spain. The analysis is complemented by a study of
  continuum images covering the disk passage of the active region, which
  are provided by the Helioseismic and Magnetic Imager on board the Solar
  Dynamics Observatory. <BR /> Results: The sunspot shows a light bridge
  with penumbral continuum intensity that separates the central umbra from
  a smaller umbra. We find that in this region the magnetic field lines
  form a canopy with lower magnetic field strength in the inner part. The
  photospheric light bridge is dominated by gas pressure (high-β),
  as opposed to the surrounding umbra, where the magnetic pressure
  is higher. A convective flow is observed in the light bridge. This
  flow is able to bend the magnetic field lines and to produce field
  reversals. The field lines merge above the light bridge and become
  as vertical and strong as in the surrounding umbra. We conclude that
  this occurs because two highly magnetized regions approach each other
  during the sunspot evolution. <P />Movies associated to Figs. 2 and 13
  are available at <A href="http://www.aanda.org">http://www.aanda.org</A>

Title: Inference of magnetic fields in the very quiet Sun
Authors: Martínez González, M. J.; Pastor Yabar, A.; Lagg, A.;
   Asensio Ramos, A.; Collados, M.; Solanki, S. K.; Balthasar, H.;
   Berkefeld, T.; Denker, C.; Doerr, H. P.; Feller, A.; Franz, M.;
   González Manrique, S. J.; Hofmann, A.; Kneer, F.; Kuckein, C.;
   Louis, R.; von der Lühe, O.; Nicklas, H.; Orozco, D.; Rezaei, R.;
   Schlichenmaier, R.; Schmidt, D.; Schmidt, W.; Sigwarth, M.; Sobotka,
   M.; Soltau, D.; Staude, J.; Strassmeier, K. G.; Verma, M.; Waldman,
   T.; Volkmer, R.
Bibcode: 2016A&A...596A...5M
Altcode: 2018arXiv180410089M
  Context. Over the past 20 yr, the quietest areas of the solar surface
  have revealed a weak but extremely dynamic magnetism occurring
  at small scales (&lt;500 km), which may provide an important
  contribution to the dynamics and energetics of the outer layers of
  the atmosphere. Understanding this magnetism requires the inference
  of physical quantities from high-sensitivity spectro-polarimetric
  data with high spatio-temporal resolution. <BR /> Aims: We present
  high-precision spectro-polarimetric data with high spatial resolution
  (0.4'') of the very quiet Sun at 1.56 μm obtained with the GREGOR
  telescope to shed some light on this complex magnetism. <BR /> Methods:
  We used inversion techniques in two main approaches. First, we assumed
  that the observed profiles can be reproduced with a constant magnetic
  field atmosphere embedded in a field-free medium. Second, we assumed
  that the resolution element has a substructure with either two constant
  magnetic atmospheres or a single magnetic atmosphere with gradients of
  the physical quantities along the optical depth, both coexisting with
  a global stray-light component. <BR /> Results: Half of our observed
  quiet-Sun region is better explained by magnetic substructure within
  the resolution element. However, we cannot distinguish whether this
  substructure comes from gradients of the physical parameters along the
  line of sight or from horizontal gradients (across the surface). In
  these pixels, a model with two magnetic components is preferred, and
  we find two distinct magnetic field populations. The population with
  the larger filling factor has very weak ( 150 G) horizontal fields
  similar to those obtained in previous works. We demonstrate that the
  field vector of this population is not constrained by the observations,
  given the spatial resolution and polarimetric accuracy of our data. The
  topology of the other component with the smaller filling factor is
  constrained by the observations for field strengths above 250 G:
  we infer hG fields with inclinations and azimuth values compatible
  with an isotropic distribution. The filling factors are typically
  below 30%. We also find that the flux of the two polarities is not
  balanced. From the other half of the observed quiet-Sun area 50% are
  two-lobed Stokes V profiles, meaning that 23% of the field of view
  can be adequately explained with a single constant magnetic field
  embedded in a non-magnetic atmosphere. The magnetic field vector and
  filling factor are reliable inferred in only 50% based on the regular
  profiles. Therefore, 12% of the field of view harbour hG fields with
  filling factors typically below 30%. At our present spatial resolution,
  70% of the pixels apparently are non-magnetised.

Title: Fitting peculiar spectral profiles in He I 10830Å absorption
    features
Authors: González Manrique, S. J.; Kuckein, C.; Pastor Yabar, A.;
   Collados, M.; Denker, C.; Fischer, C. E.; Gömöry, P.; Diercke, A.;
   Bello González, N.; Schlichenmaier, R.; Balthasar, H.; Berkefeld, T.;
   Feller, A.; Hoch, S.; Hofmann, A.; Kneer, F.; Lagg, A.; Nicklas, H.;
   Orozco Suárez, D.; Schmidt, D.; Schmidt, W.; Sigwarth, M.; Sobotka,
   M.; Solanki, S. K.; Soltau, D.; Staude, J.; Strassmeier, K. G.; Verma,
   M.; Volkmer, R.; von der Lühe, O.; Waldmann, T.
Bibcode: 2016AN....337.1057G
Altcode: 2016arXiv160300679G
  The new generation of solar instruments provides better
  spectral, spatial, and temporal resolution for a better
  understanding of the physical processes that take place on the
  Sun. Multiple-component profiles are more commonly observed with these
  instruments. Particularly, the He I 10830 Å triplet presents such
  peculiar spectral profiles, which give information on the velocity
  and magnetic fine structure of the upper chromosphere. The purpose
  of this investigation is to describe a technique to efficiently fit
  the two blended components of the He I 10830 Å triplet, which are
  commonly observed when two atmospheric components are located within
  the same resolution element. The observations used in this study were
  taken on 2015 April 17 with the very fast spectroscopic mode of the
  GREGOR Infrared Spectrograph (GRIS) attached to the 1.5-m GREGOR solar
  telescope, located at the Observatorio del Teide, Tenerife, Spain. We
  apply a double-Lorentzian fitting technique using Levenberg-Marquardt
  least-squares minimization. This technique is very simple and much
  faster than inversion codes. Line-of-sight Doppler velocities can
  be inferred for a whole map of pixels within just a few minutes. Our
  results show sub- and supersonic downflow velocities of up to 32 km
  s<SUP>-1</SUP> for the fast component in the vicinity of footpoints of
  filamentary structures. The slow component presents velocities close
  to rest.

Title: The vertical thickness of Jupiter's Europa gas torus from
    charged particle measurements
Authors: Kollmann, P.; Paranicas, C.; Clark, G.; Roussos, E.; Lagg,
   A.; Krupp, N.
Bibcode: 2016GeoRL..43.9425K
Altcode:
  Measurements and modeling suggest the presence of a neutral gas torus
  collocated with the orbit of Jupiter's moon Europa. Here we use data
  from the CMS instrument that is part of the Energetic Particles Detector
  (EPD) on board the Galileo spacecraft to characterize the distribution
  of 130 keV protons. Near the orbit of Europa this distribution has a
  minimum around 70° in equatorial pitch angle. We reproduce this with
  a model assuming that the protons are lost via charge exchange with
  a gas torus. Since the pitch angle characterizes whether the protons
  remain mostly in the dense center of the torus or continuously bounce
  through it, we can determine the latitudinal extent of the torus. We
  find that the full thickness where its density falls to 1/e of its
  maximum has to be ≲2RJ and is closer to ≈1R<SUB>J</SUB>.

Title: Formation of a solar Hα filament from orphan penumbrae
Authors: Buehler, D.; Lagg, A.; van Noort, M.; Solanki, S. K.
Bibcode: 2016A&A...589A..31B
Altcode: 2016arXiv160305899B
  <BR /> Aims: The formation and evolution of an Hα filament in active
  region (AR) 10953 is described. <BR /> Methods: Observations from the
  Solar Optical Telescope (SOT) aboard the Hinode satellite starting
  from UT 18:09 on 27th April 2007 until UT 06:08 on 1st May 2007 were
  analysed. 20 scans of the 6302 Å Fe I line pair recorded by SOT/SP were
  inverted using the spatially coupled version of the SPINOR code. The
  inversions were analysed together with co-spatial SOT/BFI G-band and
  Ca II H and SOT/NFI Hα observations. <BR /> Results: Following the
  disappearance of an initial Hα filament aligned along the polarity
  inversion line (PIL) of the AR, a new Hα filament formed in its place
  some 20 h later, which remained stable for, at least, another 1.5
  days. The creation of the new Hα filament was driven by the ascent of
  horizontal magnetic fields from the photosphere into the chromosphere
  at three separate locations along the PIL. The magnetic fields at
  two of these locations were situated directly underneath the initial
  Hα filament and formed orphan penumbrae already aligned along the Hα
  filament channel. The 700 G orphan penumbrae were stable and trapped in
  the photosphere until the disappearance of the overlying initial Hα
  filament, after which they started to ascend into the chromosphere at
  10 ± 5 m/s. Each ascent was associated with a simultaneous magnetic
  flux reduction of up to 50% in the photosphere. The ascended orphan
  penumbrae formed dark seed structures in Hα in parallel with the PIL,
  which elongated and merged to form an Hα filament. The filament channel
  featured horizontal magnetic fields of on average 260 G at log (τ) =
  -2 suspended above the nearly field-free lower photosphere. The fields
  took on an overall inverse configuration at log (τ) = -2 suggesting
  a flux rope topology for the new Hα filament. The destruction of the
  initial Hα filament was likely caused by the flux emergence at the
  third location along the PIL. <BR /> Conclusions: We present a new
  interpretation of the Hα filament formation in AR 10953 whereby the
  mainly horizontal fields of orphan penumbrae, aligned along the Hα
  filament channel, ascend into the chromosphere, forming seed fragments
  for a new, second Hα filament. The orphan penumbral fields ascend
  into the chromosphere ~9-24 h before the Hα filament is fully formed.

Title: Flows in and around Active Region NOAA12118 Observed with
    the GREGOR Solar Telescope and SDO/HMI
Authors: Verma, M.; Denker, C.; Balthasar, H.; Kuckein, C.; González
   Manrique, S. J.; Sobotka, M.; Bello González, N.; Hoch, S.; Diercke,
   A.; Kummerow, P.; Berkefeld, T.; Collados, M.; Feller, A.; Hofmann,
   A.; Kneer, F.; Lagg, A.; Löhner-Böttcher, J.; Nicklas, H.; Pastor
   Yabar, A.; Schlichenmaier, R.; Schmidt, D.; Schmidt, W.; Schubert,
   M.; Sigwarth, M.; Solanki, S. K.; Soltau, D.; Staude, J.; Strassmeier,
   K.; Volkmer, R.; von der Lühe, O.; Waldmann, T.
Bibcode: 2016ASPC..504...29V
Altcode: 2016arXiv160301109V
  Accurate measurements of magnetic and velocity fields in and around
  solar active regions are key to unlocking the mysteries of the
  formation and the decay of sunspots. High spatial resolution images
  and spectral sequences with a high cadence obtained with the GREGOR
  solar telescope give us an opportunity to scrutinize 3-D flow fields
  with local correlation tracking and imaging spectroscopy. We present
  GREGOR early science data acquired in 2014 July - August with the GREGOR
  Fabry-Pérot Interferometer and the Blue Imaging Channel. Time-series
  of blue continuum (λ 450.6 nm) images of the small active region
  NOAA 12118 were restored with the speckle masking technique to derive
  horizontal proper motions and to track the evolution of morphological
  changes. In addition, high-resolution observations are discussed in
  the context of synoptic data from the Solar Dynamics Observatory.

Title: Depth-dependent global properties of a sunspot observed by
    Hinode using the Solar Optical Telescope/Spectropolarimeter
Authors: Tiwari, Sanjiv K.; van Noort, Michiel; Solanki, Sami K.;
   Lagg, Andreas
Bibcode: 2015A&A...583A.119T
Altcode: 2015arXiv150804830T
  Context. For the past two decades, the three-dimensional structure
  of sunspots has been studied extensively. A recent improvement in the
  Stokes inversion technique prompts us to revisit the depth-dependent
  properties of sunspots. <BR /> Aims: In the present work, we aim to
  investigate the global depth-dependent thermal, velocity, and magnetic
  properties of a sunspot, as well as the interconnection between
  various local properties. <BR /> Methods: We analysed high-quality
  Stokes profiles of the disk-centred, regular, leading sunspot of NOAA
  AR 10933, acquired by the Solar Optical Telescope/Spectropolarimeter
  (SOT/SP) on board the Hinode spacecraft. To obtain depth-dependent
  stratification of the physical parameters, we used the recently
  developed, spatially coupled version of the SPINOR inversion code. <BR
  /> Results: First, we study the azimuthally averaged physical parameters
  of the sunspot. We find that the vertical temperature gradient in the
  lower- to mid-photosphere is at its weakest in the umbra, while it is
  considerably stronger in the penumbra, and stronger still in the spot's
  surroundings. The azimuthally averaged field becomes more horizontal
  with radial distance from the centre of the spot, but more vertical
  with height. At continuum optical depth unity, the line-of-sight
  velocity shows an average upflow of ~300 ms<SUP>-1</SUP> in the inner
  penumbra and an average downflow of ~1300 ms<SUP>-1</SUP> in the
  outer penumbra. The downflow continues outside the visible penumbral
  boundary. The sunspot shows, at most, a moderate negative twist of
  &lt;5° at log (τ) = 0, which increases with height. The sunspot umbra
  and the spines of the penumbra show considerable similarity with regard
  to their physical properties, albeit with some quantitative differences
  (weaker, somewhat more horizontal fields in spines, commensurate
  with their location being further away from the sunspot's core). The
  temperature shows a general anti-correlation with the field strength,
  with the exception of the heads of penumbral filaments, where a weak
  positive correlation is found. The dependence of the physical parameters
  on each other over the full sunspot shows a qualitative similarity to
  that of a standard penumbral filament and its surrounding spines. <BR />
  Conclusions: The large-scale variation in the physical parameters of
  a sunspot at various optical depths is presented. Our results suggest
  that the spines in the penumbra are basically the outward extension
  of the umbra. The spines and the penumbral filaments, together, are
  the basic elements that form a sunspot penumbra.

Title: Statistical analysis of supersonic downflows in sunspot
    penumbrae.
Authors: Kim, Hyunnam; Lagg, Andreas; Solanki, Sami K.; Narayan,
   Gautam; van Noort, Michiel; Kim, Kap-Sung
Bibcode: 2015IAUGA..2254868K
Altcode:
  Supersonic downflow patches was found in the outer edge of sunspot
  penumbra. These patches are believed to be the return channels of the
  Evershed flow. There was previous study to investigate their structure
  in detail using Hinode SOT/SP observations (M. van Noort et al. 2013)
  but their data sample was only two sunspots. To make general description
  it needs to check more sunspot data sample.We selected 242 downflow
  patches of 16 sunspots using Hinode SOT/SP observations from 2006 to
  2012. Height-dependent maps of atmospheric parameters of these downflows
  was produced by using HeLix which was height dependent LTE inversion
  code of Stokes profiles.Statistical analysis of magnetic field strength,
  inclination angle of field line, temperature and line-of-sight velocity
  are presented. The recovered atmospheric data tell us that downflow
  patches have different physical signatures comparing normal penumbra
  properties. Furthermore, our results of three height-dependent layer
  support that heating process should occur on the downflow patches in
  the middle of layer.

Title: Using Realistic MHD Simulations for Modeling and Interpretation
    of Quiet-Sun Observations with the Solar Dynamics Observatory
    Helioseismic and Magnetic Imager
Authors: Kitiashvili, I. N.; Couvidat, S.; Lagg, A.
Bibcode: 2015ApJ...808...59K
Altcode: 2014arXiv1407.2663K
  The solar atmosphere is extremely dynamic, and many important phenomena
  develop on small scales that are unresolved in observations with
  the Helioseismic and Magnetic Imager (HMI) instrument on the Solar
  Dynamics Observatory. For correct calibration and interpretation of
  the observations, it is very important to investigate the effects
  of small-scale structures and dynamics on the HMI observables,
  such as Doppler shift, continuum intensity, spectral line depth,
  and width. We use 3D radiative hydrodynamics simulations of the
  upper turbulent convective layer and the atmosphere of the Sun, and
  a spectro-polarimetric radiative transfer code to study observational
  characteristics of the Fe i 6173 Å line observed by HMI in quiet-Sun
  regions. We use the modeling results to investigate the sensitivity
  of the line Doppler shift to plasma velocity, and also sensitivities
  of the line parameters to plasma temperature and density, and
  determine effective line formation heights for observations of solar
  regions located at different distances from the disk center. These
  estimates are important for the interpretation of helioseismology
  measurements. In addition, we consider various center-to-limb effects,
  such as convective blueshift, variations of helioseismic travel-times,
  and the “concave” Sun effect, and show that the simulations can
  qualitatively reproduce the observed phenomena, indicating that these
  effects are related to a complex interaction of the solar dynamics
  and radiative transfer.

Title: Variation in sunspot properties between 1999 and 2014
Authors: Rezaei, R.; Beck, C.; Lagg, A.; Borrero, J. M.; Schmidt,
   W.; Collados, M.
Bibcode: 2015A&A...578A..43R
Altcode:
  <BR /> Aims: We study the variation in the magnetic field strength,
  area, and continuum intensity of umbrae in solar cycles 23 and 24. <BR
  /> Methods: We analyzed a sample of 374 sunspots observed from 1999
  until 2014 with the Tenerife Infrared Polarimeter at the German
  Vacuum Tower Telescope and the Facility InfRared Spectropolarimeter
  at the Dunn Solar Telescope. The sample of field strength, area,
  and intensities was used to trace any long-term or cyclic trend of
  umbral properties in the last 15 years. <BR /> Results: Sunspots
  are systematically weaker, that is, have a weaker field strength and
  stronger continuum intensity, toward the end of cycle 23 than they
  had at the maximum of cycle 23. The linear trend reverses with the
  onset of cycle 24. We find that the field strength decreases in the
  declining phase of cycle 23 by about 112 (± 16) G yr<SUP>-1</SUP>,
  while it increases in the rising phase of cycle 24 by about 138 (±
  72) G yr<SUP>-1</SUP>. The umbral intensity shows the opposite trend:
  the intensity increases with a rate of 0.7 (± 0.3)% of I<SUB>c</SUB>
  yr<SUP>-1</SUP> toward the end of cycle 23 and decreases with a rate
  of 3.8 (± 1.5)% of I<SUB>c</SUB> yr<SUP>-1</SUP> toward the maximum of
  cycle 24. The distribution of the umbral maximum field strength in cycle
  24 is similar to that of cycle 23, but is slightly shifted toward lower
  values by about 80 G, corresponding to a possible long-term gradient in
  umbral field strength of about 7 ± 4 G yr<SUP>-1</SUP>. If instead of
  the maximum umbral field we consider the average value over the entire
  umbra, the distribution shifts by about 44 Gauss. <BR /> Conclusions:
  The umbral brightness decreases in the rising stage of a solar cycle,
  but increases from maximum toward the end of the cycle. Our results
  do not indicate a drastic change of the solar cycle toward a grand
  minimum in the near future.

Title: Properties of solar plage from a spatially coupled inversion
    of Hinode SP data
Authors: Buehler, D.; Lagg, A.; Solanki, S. K.; van Noort, M.
Bibcode: 2015A&A...576A..27B
Altcode: 2015arXiv150101151B
  <BR /> Aims: The properties of magnetic fields forming an extended
  plage region in AR 10953 were investigated. <BR /> Methods:
  Stokes spectra of the Fe I line pair at 6302 Å recorded by the
  spectropolarimeter aboard the Hinode satellite were inverted using
  the SPINOR code. The code performed a 2D spatially coupled inversion
  on the Stokes spectra, allowing the retrieval of gradients in optical
  depth within the atmosphere of each pixel, whilst accounting for the
  effects of the instrument's PSF. Consequently, no magnetic filling
  factor was needed. <BR /> Results: The inversion results reveal that
  plage is composed of magnetic flux concentrations (MFCs) with typical
  field strengths of 1520 G at log (τ) = -0.9 and inclinations of
  10°-15°. The MFCs expand by forming magnetic canopies composed of
  weaker and more inclined magnetic fields. The expansion and average
  temperature stratification of isolated MFCs can be approximated well
  with an empirical plage thin flux tube model. The highest temperatures
  of MFCs are located at their edges in all log (τ) layers. Whilst
  the plasma inside MFCs is nearly at rest, each is surrounded by a
  ring of downflows of on average 2.4 km s<SUP>-1</SUP> at log (τ)
  = 0 and peak velocities of up to 10 km s<SUP>-1</SUP>, which are
  supersonic. The downflow ring of an MFC weakens and shifts outwards
  with height, tracing the MFC's expansion. Such downflow rings often
  harbour magnetic patches of opposite polarity to that of the main MFC
  with typical field strengths below 300 G at log (τ) = 0. These opposite
  polarity patches are situated beneath the canopy of their main MFC. We
  found evidence of a strong broadening of the Stokes profiles in MFCs
  and particularly in the downflow rings surrounding MFCs (expressed
  by a microturbulence in the inversion). This indicates the presence
  of strong unresolved velocities. Larger magnetic structures such as
  sunspots cause the field of nearby MFCs to be more inclined.

Title: Comparison of inversion codes for polarized line formation
    in MHD simulations. I. Milne-Eddington codes
Authors: Borrero, J. M.; Lites, B. W.; Lagg, A.; Rezaei, R.; Rempel, M.
Bibcode: 2014A&A...572A..54B
Altcode: 2014arXiv1409.3376B
  Milne-Eddington (M-E) inversion codes for the radiative transfer
  equation are the most widely used tools to infer the magnetic field
  from observations of the polarization signals in photospheric and
  chromospheric spectral lines. Unfortunately, a comprehensive comparison
  between the different M-E codes available to the solar physics
  community is still missing, and so is a physical interpretation of their
  inferences. In this contribution we offer a comparison between three
  of those codes (VFISV, ASP/HAO, and HeLIx<SUP>+</SUP>). These codes are
  used to invert synthetic Stokes profiles that were previously obtained
  from realistic non-grey three-dimensional magnetohydrodynamical (3D MHD)
  simulations. The results of the inversion are compared with each other
  and with those from the MHD simulations. In the first case, the M-E
  codes retrieve values for the magnetic field strength, inclination and
  line-of-sight velocity that agree with each other within σ<SUB>B</SUB>
  ≤ 35 (Gauss), σ<SUB>γ</SUB> ≤ 1.2°, and σ<SUB>v</SUB> ≤
  10 m s<SUP>-1</SUP>, respectively. Additionally, M-E inversion codes
  agree with the numerical simulations, when compared at a fixed optical
  depth, within σ<SUB>B</SUB> ≤ 130 (Gauss), σ<SUB>γ</SUB> ≤ 5°,
  and σ<SUB>v</SUB> ≤ 320 m s<SUP>-1</SUP>. Finally, we show that
  employing generalized response functions to determine the height at
  which M-E codes measure physical parameters is more meaningful than
  comparing at a fixed geometrical height or optical depth. In this case
  the differences between M-E inferences and the 3D MHD simulations
  decrease to σ<SUB>B</SUB> ≤ 90 (Gauss), σ<SUB>γ</SUB> ≤ 3°,
  and σ<SUB>v</SUB> ≤ 90 m s<SUP>-1</SUP>.

Title: Inclinations of small quiet-Sun magnetic features based on
    a new geometric approach
Authors: Jafarzadeh, S.; Solanki, S. K.; Lagg, A.; Bellot Rubio,
   L. R.; van Noort, M.; Feller, A.; Danilovic, S.
Bibcode: 2014A&A...569A.105J
Altcode: 2014arXiv1408.2443J
  Context. High levels of horizontal magnetic flux have been reported
  in the quiet-Sun internetwork, often based on Stokes profile
  inversions. <BR /> Aims: Here we introduce a new method for deducing
  the inclination of magnetic elements and use it to test magnetic field
  inclinations from inversions. <BR /> Methods: We determine accurate
  positions of a set of small, bright magnetic elements in high spatial
  resolution images sampling different photospheric heights obtained by
  the Sunrise balloon-borne solar observatory. Together with estimates
  of the formation heights of the employed spectral bands, these provide
  us with the inclinations of the magnetic features. We also compute
  the magnetic inclination angle of the same magnetic features from the
  inversion of simultaneously recorded Stokes parameters. <BR /> Results:
  Our new, geometric method returns nearly vertical fields (average
  inclination of around 14° with a relatively narrow distribution
  having a standard deviation of 6°). In strong contrast to this, the
  traditionally used inversions give almost horizontal fields (average
  inclination of 75 ± 8°) for the same small magnetic features,
  whose linearly polarised Stokes profiles are adversely affected by
  noise. We show that for such magnetic features inversions overestimate
  the flux in horizontal magnetic fields by an order of magnitude. <BR />
  Conclusions: The almost vertical field of bright magnetic features from
  our geometric method is clearly incompatible with the nearly horizontal
  magnetic fields obtained from the inversions. This indicates that the
  amount of magnetic flux in horizontal fields deduced from inversions is
  overestimated in the presence of weak Stokes signals, in particular if
  Stokes Q and U are close to or under the noise level. Inversions should
  be used with great caution when applied to data with no clear Stokes Q
  and no U signal. By combining the proposed method with inversions we are
  not just improving the inclination, but also the field strength. This
  technique allows us to analyse features that are not reliably treated
  by inversions, thus greatly extending our capability to study the
  complete magnetic field of the quiet Sun.

Title: Vigorous convection in a sunspot granular light bridge
Authors: Lagg, Andreas; Solanki, Sami K.; van Noort, Michiel;
   Danilovic, Sanja
Bibcode: 2014A&A...568A..60L
Altcode: 2014arXiv1407.1202L
  Context. Light bridges are the most prominent manifestation of
  convection in sunspots. The brightest representatives are granular
  light bridges composed of features that appear to be similar to
  granules. <BR /> Aims: An in-depth study of the convective motions,
  temperature stratification, and magnetic field vector in and around
  light bridge granules is presented with the aim of identifying
  similarities and differences to typical quiet-Sun granules. <BR />
  Methods: Spectropolarimetric data from the Hinode Solar Optical
  Telescope were analyzed using a spatially coupled inversion technique
  to retrieve the stratified atmospheric parameters of light bridge and
  quiet-Sun granules. <BR /> Results: Central hot upflows surrounded by
  cooler fast downflows reaching 10 km s<SUP>-1</SUP> clearly establish
  the convective nature of the light bridge granules. The inner part
  of these granules in the near surface layers is field free and is
  covered by a cusp-like magnetic field configuration. We observe
  hints of field reversals at the location of the fast downflows. The
  quiet-Sun granules in the vicinity of the sunspot are covered by a
  low-lying canopy field extending radially outward from the spot. <BR
  /> Conclusions: The similarities between quiet-Sun and light bridge
  granules point to the deep anchoring of granular light bridges in
  the underlying convection zone. The fast, supersonic downflows are
  most likely a result of a combination of invigorated convection
  in the light bridge granule due to radiative cooling into the
  neighboring umbra and the fact that we sample deeper layers, since the
  downflows are immediately adjacent to the slanted walls of the Wilson
  depression. <P />The two movies are available in electronic form at <A
  href="http://www.aanda.org/10.1051/0004-6361/201424071/olm">http://www.aanda.org</A>

Title: Migration of Ca II H bright points in the internetwork
Authors: Jafarzadeh, S.; Cameron, R. H.; Solanki, S. K.; Pietarila,
   A.; Feller, A.; Lagg, A.; Gandorfer, A.
Bibcode: 2014A&A...563A.101J
Altcode: 2014arXiv1401.7522J
  Context. The migration of magnetic bright point-like features (MBP)
  in the lower solar atmosphere reflects the dispersal of magnetic
  flux as well as the horizontal flows of the atmospheric layer they
  are embedded in. <BR /> Aims: We analyse trajectories of the proper
  motion of intrinsically magnetic, isolated internetwork Ca ii H MBPs
  (mean lifetime 461 ± 9 s) to obtain their diffusivity behaviour. <BR
  /> Methods: We use seeing-free high spatial and temporal resolution
  image sequences of quiet-Sun, disc-centre observations obtained in
  the Ca ii H 3968 Å passband of the Sunrise Filter Imager (SuFI)
  onboard the Sunrise balloon-borne solar observatory. Small MBPs in
  the internetwork are automatically tracked. The trajectory of each
  MBP is then calculated and described by a diffusion index (γ) and
  a diffusion coefficient (D). We also explore the distribution of the
  diffusion indices with the help of a Monte Carlo simulation. <BR />
  Results: We find γ = 1.69 ± 0.08 and D = 257 ± 32 km<SUP>2</SUP>
  s<SUP>-1</SUP> averaged over all MBPs. Trajectories of most MBPs are
  classified as super-diffusive, i.e. γ &gt; 1, with the determined γ
  being the largest obtained so far to our knowledge. A direct correlation
  between D and timescale (τ) determined from trajectories of all MBPs is
  also obtained. We discuss a simple scenario to explain the diffusivity
  of the observed, relatively short-lived MBPs while they migrate within
  a small area in a supergranule (i.e. an internetwork area). We show
  that the scatter in the γ values obtained for individual MBPs is due
  to their limited lifetimes. <BR /> Conclusions: The super-diffusive
  MBPs can be described as random walkers (due to granular evolution and
  intergranular turbulence) superposed on a large systematic (background)
  velocity, caused by granular, mesogranular, and supergranular flows.

Title: Magnetic structure of an activated filament in a flaring
    active region
Authors: Sasso, C.; Lagg, A.; Solanki, S. K.
Bibcode: 2014A&A...561A..98S
Altcode: 2013arXiv1312.2781S
  <BR /> Aims: While the magnetic field in quiescent prominences has
  been widely investigated, less is known about the field in activated
  prominences. We report observational results on the magnetic field
  structure of an activated filament in a flaring active region. In
  particular, we studied its magnetic structure and line-of-sight flows
  during its early activated phase, shortly before it displayed signs
  of rotation. <BR /> Methods: We inverted the Stokes profiles of the
  chromospheric He i 10 830 Å triplet and the photospheric Si i 10 827
  Å line observed in this filament by the Vacuum Tower Telescope on
  Tenerife. Using these inversion results, we present and interpret the
  first maps of the velocity and magnetic field obtained in an activated
  filament, both in the photosphere and the chromosphere. <BR /> Results:
  Up to five different magnetic components are found in the chromospheric
  layers of the filament, while outside the filament a single component is
  sufficient to reproduce the observations. Magnetic components displaying
  an upflow are preferentially located towards the centre of the filament,
  while the downflows are concentrated along its periphery. Moreover,
  the upflowing gas is associated with an opposite-polarity magnetic
  configuration with respect to the photosphere, while the downflowing gas
  is associated with a same-polarity configuration. <BR /> Conclusions:
  The activated filament has a very complex structure. Nonetheless,
  it is compatible with a flux rope, albeit a distorted one, in
  the normal configuration. The observations are best explained
  by a rising flux rope in which part of the filament material is
  still stably stored (upflowing material, rising with the field),
  while the rest is no longer stably stored and flows down along the
  field lines. <P />The movie is available in electronic form at <A
  href="http://www.aanda.org/10.1051/0004-6361/201322481/olm">http://www.aanda.org</A>

Title: Analysis of magnetic fields in a plage region using a spatially
    coupled 2D inversion technique
Authors: Buehler, David; Lagg, Andreas; Solanki, Sami K.; Van Noort,
   Michiel
Bibcode: 2014cosp...40E.427B
Altcode:
  The properties of magnetic features (MFCs) within a plage region
  in the vicinity of a sunspot were investigated at high spatial
  resolution. Stokes spectra of the 630nm line pair recorded by the
  spectropolarimeter aboard Hinode were inverted using an extended
  version of the SPINOR code. The code preformed a spatially coupled
  inversion of the Stokes spectra using three log(tau) nodes in optical
  depth. No magnetic filling factors was employed. The analysis of the
  inversion results reveals that the MFCs have typical field strengths
  of 1500G at log(tau)=-0.9 and inclinations between 10-15 degrees in
  all three log(tau) nodes. The MFCs expand by forming magnetic canopies
  composed of weaker and more inclined magnetic fields. The expansion of
  the magnetic field and temperature stratification of MFCs with optical
  depth is in good agreement with a thin flux tube model. Whilst the gas
  inside magnetic flux concentrations is typically at rest, the majority
  of MFCs were surrounded by a ring of downflows with an average value
  of 2.5km/s at log(tau)=0. The ring gradually shifts outwards following
  the expansion of the MFC. Within the downflow rings of MFCs small
  magnetic patches of opposite polarity to that of the main MFC were
  identified, which are predominantly situated beneath the canopy of
  its main MFC. We found evidence for a strong broadening of the Stokes
  profiles within MFCs and their surrounding downflow rings (expressed
  by a microturbulence in the inversion). This indicates the presence
  of strong unresolved velocities.

Title: Peripheral downflows in sunspot penumbrae
Authors: van Noort, M.; Lagg, A.; Tiwari, S. K.; Solanki, S. K.
Bibcode: 2013A&A...557A..24V
Altcode: 2013arXiv1308.0466V
  Context. Sunspot penumbrae show high-velocity patches along
  the periphery. <BR /> Aims: The high-velocity downflow patches
  are believed to be the return channels of the Evershed flow. We
  aim to investigate their structure in detail using Hinode SOT/SP
  observations. <BR /> Methods: We employ Fourier interpolation in
  combination with spatially coupled height dependent LTE inversions
  of Stokes profiles to produce high-resolution, height-dependent maps
  of atmospheric parameters of these downflows and investigate their
  properties. <BR /> Results: High-speed downflows are observed over
  a wide range of viewing angles. They have supersonic line-of-sight
  velocities, some in excess of 20 km s<SUP>-1</SUP>, and very high
  magnetic field strengths, reaching values of over 7 kG. A relation
  between the downflow velocities and the magnetic field strength is
  found, in good agreement with MHD simulations. <BR /> Conclusions:
  The coupled inversion at high resolution allows for the accurate
  determination of small-scale structures. The recovered atmospheric
  structure indicates that regions with very high downflow velocities
  contain some of the strongest magnetic fields that have ever been
  measured on the Sun. <P />Two movies are available in electronic form
  at <A href="http://www.aanda.org">http://www.aanda.org</A>

Title: Structure of sunspot penumbral filaments: a remarkable
    uniformity of properties
Authors: Tiwari, Sanjiv Kumar; van Noort, Michiel; Lagg, Andreas;
   Solanki, Sami K.
Bibcode: 2013A&A...557A..25T
Altcode: 2013arXiv1307.3668T
  Context. The sunspot penumbra comprises numerous thin, radially
  elongated filaments that are central for heat transport within
  the penumbra, but whose structure is still not clear. <BR /> Aims:
  We aim to investigate the fine-scale structure of these penumbral
  filaments. <BR /> Methods: We perform a depth-dependent inversion of
  spectropolarimetric data of a sunspot very close to solar disk center
  obtained by Solar Optical Telescope/Spectropolarimeter onboard the
  Hinode spacecraft. We have used a recently developed, spatially coupled
  2D inversion scheme, which allows us to analyze the fine structure
  of individual penumbral filaments up to the diffraction limit of
  the telescope. <BR /> Results: Filaments of different sizes in all
  parts of the penumbra display very similar magnetic field strengths,
  inclinations, and velocity patterns. The temperature structure is also
  similar, although the filaments in the inner penumbra have cooler
  tails than those in the outer penumbra. The similarities allowed
  us to average all these filaments and to subsequently extract the
  physical properties common to all of them. This average filament
  shows upflows associated with an upward-pointing field at its inner,
  umbral end (head) and along its axis, as well as downflows along the
  lateral edge and strong downflows in the outer end (tail) associated
  with a nearly vertical, strong, and downward-pointing field. The
  upflowing plasma is significantly, i.e., up to 800 K, hotter than the
  downflowing plasma. The hot, tear-shaped head of the averaged filament
  can be associated with a penumbral grain. The central part of the
  filament shows nearly horizontal fields with strengths in the range
  of 1 kG. The field above the filament converges, whereas a diverging
  trend is seen in the deepest layers near the head of the filament. The
  fluctuations in the physical parameters along and across the filament
  increase rapidly with depth. <BR /> Conclusions: We put forward a
  unified observational picture of a sunspot penumbral filament. It
  is consistent with such a filament being a magneto-convective cell,
  in line with recent magnetohydrodynamic simulations. The uniformity
  of its properties over the penumbra sets constraints on penumbral
  models and simulations. The complex and inhomogeneous structure of the
  filament provides a natural explanation for a number of long-running
  controversies in the literature.

Title: Quiet Sun magnetic fields observed by Hinode: Support for a
    local dynamo
Authors: Buehler, D.; Lagg, A.; Solanki, S. K.
Bibcode: 2013A&A...555A..33B
Altcode: 2013arXiv1307.0789B
  Context. The Hinode mission has revealed copious amounts of horizontal
  flux covering the quiet Sun. Local dynamo action has been proposed
  to explain the presence of this flux. <BR /> Aims: We sought to
  test whether the quiet Sun flux detected by Hinode is due to a
  local or the global dynamo by studying long-term variations in the
  polarisation signals detectable at the disc centre of the quiet Sun
  between November 2006 and May 2012, with particular emphasis on weak
  signals in the internetwork. <BR /> Methods: The investigation focusses
  on line-integrated circular polarisation V<SUB>tot</SUB> and linear
  polarisation LP<SUB>tot</SUB> profiles obtained from the Fe I 6302.5
  Å absorption line in Hinode SOT/SP. <BR /> Results: Both circular and
  linear polarisation signals show no overall variation in the fraction
  of selected pixels from 2006 until 2012. There is also no variation
  in the magnetic flux in this interval of time. The probability density
  functions (PDF) of the line-of-sight magnetic flux can be fitted with
  a power law from 1.17 × 10<SUP>17</SUP> Mx to 8.53 × 10<SUP>18</SUP>
  Mx with index α = -1.82 ± 0.02 in 2007. The variation of α's across
  all years does not exceed a significance of 1σ. Linearly polarised
  features are also fitted with a power law, with index α = -2.60 ±
  0.06 in 2007. Indices derived from linear polarisation PDFs of other
  years also show no significant variation. <BR /> Conclusions: Our
  results show that the ubiquitous horizontal polarisation on the edges
  of bright granules seen by Hinode are invariant during the minimum of
  cycle 23. This supports the notion that the weak circular and linear
  polarisation is primarily caused by an independent local dynamo.

Title: Chromospheric magnetic field of an active region filament
    using the He I triplet and the primary observation of filaments
    (prominences) using New Vacuum Solar Tower of China
Authors: Xu, Zhi; Lagg, A.; Solanki, S.; Liu, Z.; New Vacuum Solar
   Telescope Observers
Bibcode: 2013SPD....4410504X
Altcode:
  There are two parts in my presentation. In the first part I present the
  magnetic field measurement of an active region filament using the full
  Stokes profiles of He I 10830 and Si I 10827 band when the filament in
  its stable phase. This observation was fulfilled using German Vacuum
  Tower Telescope (VTT). The vector magnetic field and Doppler velocity
  map both in the photosphere and chromosphere were observed and analyzed
  co-temporally and co-spatially. The observation findings reveal that we
  were observing the emergence of a flux rope with a subsequent formation
  of a filament. In the second part, I would like to exhibit another
  ground-based observation facility, 1m New Vacuum Solar Telescope
  (NVST) located in Fu-Xian Lake Solar Observatory of China. After
  the basic introduction including the location and instrumentations,
  I give some high lights including granulation, faculae, micro-flares,
  jets, and filaments or prominence since the first running in 2010,
  showing our potential ability to do high-resolution solar observation
  from the ground. Observation proposals from the international solar
  community are well appreciated in future.

Title: Structure and dynamics of isolated internetwork Ca II H bright
    points observed by SUNRISE
Authors: Jafarzadeh, S.; Solanki, S. K.; Feller, A.; Lagg, A.;
   Pietarila, A.; Danilovic, S.; Riethmüller, T. L.; Martínez Pillet, V.
Bibcode: 2013A&A...549A.116J
Altcode: 2012arXiv1211.4836J
  <BR /> Aims: We aim to improve our picture of the low chromosphere in
  the quiet-Sun internetwork by investigating the intensity, horizontal
  velocity, size and lifetime variations of small bright points (BPs;
  diameter smaller than 0.3 arcsec) observed in the Ca II H 3968 Å
  passband along with their magnetic field parameters, derived from
  photospheric magnetograms. <BR /> Methods: Several high-quality
  time series of disc-centre, quiet-Sun observations from the Sunrise
  balloon-borne solar telescope, with spatial resolution of around 100
  km on the solar surface, have been analysed to study the dynamics
  of BPs observed in the Ca II H passband and their dependence on the
  photospheric vector magnetogram signal. <BR /> Results: Parameters such
  as horizontal velocity, diameter, intensity and lifetime histograms of
  the isolated internetwork and magnetic Ca II H BPs were determined. Mean
  values were found to be 2.2 km s<SUP>-1</SUP>, 0.2 arcsec (≈150 km),
  1.48 ⟨ I<SUB>Ca</SUB> ⟩ and 673 s, respectively. Interestingly, the
  brightness and the horizontal velocity of BPs are anti-correlated. Large
  excursions (pulses) in horizontal velocity, up to 15 km s<SUP>-1</SUP>,
  are present in the trajectories of most BPs. These could excite kink
  waves travelling into the chromosphere and possibly the corona, which we
  estimate to carry an energy flux of 310 W m<SUP>-2</SUP>, sufficient to
  heat the upper layers, although only marginally. <BR /> Conclusions:
  The stable observing conditions of Sunrise and our technique for
  identifying and tracking BPs have allowed us to determine reliable
  parameters of these features in the internetwork. Thus we find, e.g.,
  that they are considerably longer lived than previously thought. The
  large velocities are also reliable, and may excite kink waves. Although
  these wave are (marginally) energetic enough to heat the quiet corona,
  we expect a large additional contribution from larger magnetic elements
  populating the network and partly also the internetwork.

Title: The GREGOR Solar Telescope on Tenerife
Authors: Schmidt, W.; von der Lühe, O.; Volkmer, R.; Denker, C.;
   Solanki, S. K.; Balthasar, H.; Bello González, N.; Berkefeld, T.;
   Collados Vera, M.; Hofmann, A.; Kneer, F.; Lagg, A.; Puschmann, K. G.;
   Schmidt, D.; Sobotka, M.; Soltau, D.; Strassmeier, K. G.
Bibcode: 2012ASPC..463..365S
Altcode: 2012arXiv1202.4289S
  2011 was a successful year for the GREGOR project. The telescope was
  finally completed in May with the installation of the 1.5-meter primary
  mirror. The installation of the first-light focal plane instruments was
  completed by the end of the year. At the same time, the preparations
  for the installation of the high-order adaptive optics were finished,
  its integration to the telescope is scheduled for early 2012. This
  paper describes the telescope and its instrumentation in their present
  first-light configuration, and provides a brief overview of the science
  goals of GREGOR.

Title: The GREGOR Solar Telescope
Authors: Denker, C.; Lagg, A.; Puschmann, K. G.; Schmidt, D.; Schmidt,
   W.; Sobotka, M.; Soltau, D.; Strassmeier, K. G.; Volkmer, R.; von
   der Luehe, O.; Solanki, S. K.; Balthasar, H.; Bello Gonzalez, N.;
   Berkefeld, T.; Collados Vera, M.; Hofmann, A.; Kneer, F.
Bibcode: 2012IAUSS...6E.203D
Altcode:
  The 1.5-meter GREGOR solar telescope is a new facility for
  high-resolution observations of the Sun. The telescope is located at the
  Spanish Observatorio del Teide on Tenerife. The telescope incorporates
  advanced designs for a foldable-tent dome, an open steel-truss telescope
  structure, and active and passive means to minimize telescope and mirror
  seeing. Solar fine structure can be observed with a dedicated suite
  of instruments: a broad-band imaging system, the "GREGOR Fabry-Perot
  Interferometer", and the "Grating Infrared Spectrograph". All post-focus
  instruments benefit from a high-order (multi-conjugate) adaptive optics
  system, which enables observations close to the diffraction limit of
  the telescope. The inclusion of a spectrograph for stellar activity
  studies and the search for solar twins expands the scientific usage
  of the GREGOR to the nighttime domain. We report on the successful
  commissioning of the telescope until the end of 2011 and the first
  steps towards science verification in 2012.

Title: A retrospective of the GREGOR solar telescope in scientific
    literature
Authors: Denker, C.; von der Lühe, O.; Feller, A.; Arlt, K.;
   Balthasar, H.; Bauer, S. -M.; Bello González, N.; Berkefeld, Th.;
   Caligari, P.; Collados, M.; Fischer, A.; Granzer, T.; Hahn, T.;
   Halbgewachs, C.; Heidecke, F.; Hofmann, A.; Kentischer, T.; Klva{ňa,
   M.; Kneer, F.; Lagg, A.; Nicklas, H.; Popow, E.; Puschmann, K. G.;
   Rendtel, J.; Schmidt, D.; Schmidt, W.; Sobotka, M.; Solanki, S. K.;
   Soltau, D.; Staude, J.; Strassmeier, K. G.; Volkmer, R.; Waldmann,
   T.; Wiehr, E.; Wittmann, A. D.; Woche, M.
Bibcode: 2012AN....333..810D
Altcode: 2012arXiv1210.3167D
  In this review, we look back upon the literature, which had the
  GREGOR solar telescope project as its subject including science cases,
  telescope subsystems, and post-focus instruments. The articles date
  back to the year 2000, when the initial concepts for a new solar
  telescope on Tenerife were first presented at scientific meetings. This
  comprehensive bibliography contains literature until the year 2012,
  i.e., the final stages of commissioning and science verification. Taking
  stock of the various publications in peer-reviewed journals and
  conference proceedings also provides the ``historical'' context
  for the reference articles in this special issue of Astronomische
  Nachrichten/Astronomical Notes.

Title: The 1.5 meter solar telescope GREGOR
Authors: Schmidt, W.; von der Lühe, O.; Volkmer, R.; Denker, C.;
   Solanki, S. K.; Balthasar, H.; Bello Gonzalez, N.; Berkefeld, Th.;
   Collados, M.; Fischer, A.; Halbgewachs, C.; Heidecke, F.; Hofmann,
   A.; Kneer, F.; Lagg, A.; Nicklas, H.; Popow, E.; Puschmann, K. G.;
   Schmidt, D.; Sigwarth, M.; Sobotka, M.; Soltau, D.; Staude, J.;
   Strassmeier, K. G.; Waldmann , T. A.
Bibcode: 2012AN....333..796S
Altcode:
  The 1.5 m telescope GREGOR opens a new window to the understanding
  of solar small-scale magnetism. The first light instrumentation
  includes the Gregor Fabry Pérot Interferometer (GFPI), a filter
  spectro-polarimeter for the visible wavelength range, the GRating
  Infrared Spectro-polarimeter (GRIS) and the Broad-Band Imager (BBI). The
  excellent performance of the first two instruments has already been
  demonstrated at the Vacuum Tower Telescope. GREGOR is Europe's largest
  solar telescope and number 3 in the world. Its all-reflective Gregory
  design provides a large wavelength coverage from the near UV up to at
  least 5 microns. The field of view has a diameter of 150 arcsec. GREGOR
  is equipped with a high-order adaptive optics system, with a subaperture
  size of 10 cm, and a deformable mirror with 256 actuators. The science
  goals are focused on, but not limited to, solar magnetism. GREGOR
  allows us to measure the emergence and disappearance of magnetic flux
  at the solar surface at spatial scales well below 100 km. Thanks to its
  spectro-polarimetric capabilities, GREGOR will measure the interaction
  between the plasma flows, different kinds of waves, and the magnetic
  field. This will foster our understanding of the processes that heat the
  chromosphere and the outer layers of the solar atmosphere. Observations
  of the surface magnetic field at very small spatial scales will shed
  light on the variability of the solar brightness.

Title: GRIS: The GREGOR Infrared Spectrograph
Authors: Collados, M.; López, R.; Páez, E.; Hernández, E.; Reyes,
   M.; Calcines, A.; Ballesteros, E.; Díaz, J. J.; Denker, C.; Lagg,
   A.; Schlichenmaier, R.; Schmidt, W.; Solanki, S. K.; Strassmeier,
   K. G.; von der Lühe, O.; Volkmer, R.
Bibcode: 2012AN....333..872C
Altcode:
  This paper describes the main characteristics of GRIS (GREGOR Infrared
  Spectrograph), the grating spectrograph installed in the recently
  inaugurated (May 2012) 1.5-meter GREGOR telescope located at the
  Observatorio del Teide in Tenerife. The spectrograph has a standard
  Czerny-Turner configuration with parabolic collimator and camera mirrors
  that belong to the same conic surface. Although nothing prevents its
  use at visible wavelengths, the spectrograph will be initially used
  in combination with the infrared detector of the Tenerife Infrared
  Polarimeter (TIP-II) in standard spectroscopic mode as well as for
  spectropolarimetric measurements.

Title: Chromospheric magnetic fields of an active region filament
Authors: Xu, Z.; Solanki, S.; Lagg, A.
Bibcode: 2012EAS....55..163X
Altcode:
  Vector magnetic fields of an active region filament are co-spatially
  and co-temporally mapped in photosphere and upper chromosphere, by
  using spectro-polarimetric observations made by Tenerife Infrared
  Polarimeter (TIP II) at the German Vacuum Tower Telescope (VTT). A
  Zeeman-based ME inversion is performed on the full Stokes vectors
  of both the photospheric Si I 1082.7 nm and the chromospheric He
  I 1083.0 nm lines. We found that the strong magnetic fields, with
  the field strength of 600 - 800 G in the He I line formation height,
  are not uncommon among AR filaments. But such strong magnetic field
  is not always found in AR filaments.

Title: First Results from the SUNRISE Mission
Authors: Solanki, S. K.; Barthol, P.; Danilovic, S.; Feller, A.;
   Gandorfer, A.; Hirzberger, J.; Jafarzadeh, S.; Lagg, A.; Riethmüller,
   T. L.; Schüssler, M.; Wiegelmann, T.; Bonet, J. A.; González,
   M. J. M.; Pillet, V. M.; Khomenko, E.; Yelles Chaouche, L.; Iniesta,
   J. C. d. T.; Domingo, V.; Palacios, J.; Knölker, M.; González,
   N. B.; Borrero, J. M.; Berkefeld, T.; Franz, M.; Roth, M.; Schmidt,
   W.; Steiner, O.; Title, A. M.
Bibcode: 2012ASPC..455..143S
Altcode:
  The SUNRISE balloon-borne solar observatory consists of a 1m aperture
  Gregory telescope, a UV filter imager, an imaging vector polarimeter,
  an image stabilization system, and further infrastructure. The first
  science flight of SUNRISE yielded high-quality data that reveal the
  structure, dynamics, and evolution of solar convection, oscillations,
  and magnetic fields at a resolution of around 100 km in the quiet
  Sun. Here we describe very briefly the mission and the first results
  obtained from the SUNRISE data, which include a number of discoveries.

Title: Solar magnetism eXplorer (SolmeX). Exploring the magnetic
    field in the upper atmosphere of our closest star
Authors: Peter, Hardi; Abbo, L.; Andretta, V.; Auchère, F.; Bemporad,
   A.; Berrilli, F.; Bommier, V.; Braukhane, A.; Casini, R.; Curdt,
   W.; Davila, J.; Dittus, H.; Fineschi, S.; Fludra, A.; Gandorfer, A.;
   Griffin, D.; Inhester, B.; Lagg, A.; Landi Degl'Innocenti, E.; Maiwald,
   V.; Sainz, R. Manso; Martínez Pillet, V; Matthews, S.; Moses, D.;
   Parenti, S.; Pietarila, A.; Quantius, D.; Raouafi, N. -E.; Raymond, J.;
   Rochus, P.; Romberg, O.; Schlotterer, M.; Schühle, U.; Solanki, S.;
   Spadaro, D.; Teriaca, L.; Tomczyk, S.; Trujillo Bueno, J.; Vial, J. -C.
Bibcode: 2012ExA....33..271P
Altcode: 2011arXiv1108.5304P; 2011ExA...tmp..134P
  The magnetic field plays a pivotal role in many fields of
  Astrophysics. This is especially true for the physics of the solar
  atmosphere. Measuring the magnetic field in the upper solar atmosphere
  is crucial to understand the nature of the underlying physical
  processes that drive the violent dynamics of the solar corona—that
  can also affect life on Earth. SolmeX, a fully equipped solar space
  observatory for remote-sensing observations, will provide the first
  comprehensive measurements of the strength and direction of the
  magnetic field in the upper solar atmosphere. The mission consists
  of two spacecraft, one carrying the instruments, and another one in
  formation flight at a distance of about 200 m carrying the occulter to
  provide an artificial total solar eclipse. This will ensure high-quality
  coronagraphic observations above the solar limb. SolmeX integrates two
  spectro-polarimetric coronagraphs for off-limb observations, one in
  the EUV and one in the IR, and three instruments for observations on
  the disk. The latter comprises one imaging polarimeter in the EUV for
  coronal studies, a spectro-polarimeter in the EUV to investigate the low
  corona, and an imaging spectro-polarimeter in the UV for chromospheric
  studies. SOHO and other existing missions have investigated the emission
  of the upper atmosphere in detail (not considering polarization),
  and as this will be the case also for missions planned for the near
  future. Therefore it is timely that SolmeX provides the final piece of
  the observational quest by measuring the magnetic field in the upper
  atmosphere through polarimetric observations.

Title: Magnetic Fields of an Active Region Filament from Full Stokes
    Analysis of Si I 1082.7 nm and He I 1083.0 nm
Authors: Xu, Z.; Lagg, A.; Solanki, S.; Liu, Y.
Bibcode: 2012ApJ...749..138X
Altcode: 2012arXiv1202.4562X
  Vector magnetic fields of an active region filament in the photosphere
  and upper chromosphere are obtained from spectro-polarimetric
  observations recorded with the Tenerife Infrared Polarimeter (TIP II) at
  the German Vacuum Tower Telescope. We apply Milne-Eddington inversions
  on full Stokes vectors of the photospheric Si I 1082.7 nm and the upper
  chromospheric He I triplet at 1083.0 nm to obtain the magnetic field
  vector and velocity maps in two atmosphere layers. We find that (1) a
  complete filament was already present in Hα at the beginning of the TIP
  II data acquisition. Only a partially formed one, composed of multiple
  small threads, was present in He I. (2) The AR filament comprises two
  sections. One shows strong magnetic field intensities, about 600-800
  G in the upper chromosphere and 800-1000 G in the photosphere. The
  other exhibits only comparatively weak magnetic field strengths in both
  layers. (3) The Stokes V signal is indicative of a dip in the magnetic
  field strength close to the chromospheric PIL. (4) In the chromosphere,
  consistent upflows are found along the PIL flanked by downflows. (5)
  The transversal magnetic field is nearly parallel to the PIL in the
  photosphere and inclined by 20°-30° in the chromosphere. (6) The
  chromospheric magnetic field around the filament is found to be in
  normal configuration, while the photospheric field presents a concave
  magnetic topology. The observations are consistent with the emergence
  of a flux rope with a subsequent formation of a filament.

Title: Solar Particle Acceleration Radiation and Kinetics (SPARK). A
    mission to understand the nature of particle acceleration
Authors: Matthews, Sarah A.; Williams, David R.; Klein, Karl-Ludwig;
   Kontar, Eduard P.; Smith, David M.; Lagg, Andreas; Krucker, Sam;
   Hurford, Gordon J.; Vilmer, Nicole; MacKinnon, Alexander L.; Zharkova,
   Valentina V.; Fletcher, Lyndsay; Hannah, Iain G.; Browning, Philippa
   K.; Innes, Davina E.; Trottet, Gerard; Foullon, Clare; Nakariakov,
   Valery M.; Green, Lucie M.; Lamoureux, Herve; Forsyth, Colin; Walton,
   David M.; Mathioudakis, Mihalis; Gandorfer, Achim; Martinez-Pillet,
   Valentin; Limousin, Olivier; Verwichte, Erwin; Dalla, Silvia; Mann,
   Gottfried; Aurass, Henri; Neukirch, Thomas
Bibcode: 2012ExA....33..237M
Altcode: 2011ExA...tmp..124M
  Energetic particles are critical components of plasma populations
  found throughout the universe. In many cases particles are accelerated
  to relativistic energies and represent a substantial fraction of
  the total energy of the system, thus requiring extremely efficient
  acceleration processes. The production of accelerated particles
  also appears coupled to magnetic field evolution in astrophysical
  plasmas through the turbulent magnetic fields produced by diffusive
  shock acceleration. Particle acceleration is thus a key component
  in helping to understand the origin and evolution of magnetic
  structures in, e.g. galaxies. The proximity of the Sun and the range
  of high-resolution diagnostics available within the solar atmosphere
  offers unique opportunities to study the processes involved in particle
  acceleration through the use of a combination of remote sensing
  observations of the radiative signatures of accelerated particles, and
  of their plasma and magnetic environment. The SPARK concept targets the
  broad range of energy, spatial and temporal scales over which particle
  acceleration occurs in the solar atmosphere, in order to determine how
  and where energetic particles are accelerated. SPARK combines highly
  complementary imaging and spectroscopic observations of radiation from
  energetic electrons, protons and ions set in their plasma and magnetic
  context. The payload comprises focusing-optics X-ray imaging covering
  the range from 1 to 60 keV; indirect HXR imaging and spectroscopy
  from 5 to 200 keV, γ-ray spectroscopic imaging with high-resolution
  LaBr<SUB>3</SUB> scintillators, and photometry and source localisation
  at far-infrared wavelengths. The plasma environment of the regions
  of acceleration and interaction will be probed using soft X-ray
  imaging of the corona and vector magnetography of the photosphere
  and chromosphere. SPARK is designed for solar research. However,
  in addition it will be able to provide exciting new insights into the
  origin of particle acceleration in other regimes, including terrestrial
  gamma-ray flashes (TGF), the origin of γ-ray bursts, and the possible
  existence of axions.

Title: Diffusivity of Isolated Internetwork Ca II H Bright Points
    Observed by SuFI/SUNRISE
Authors: Jafarzadeh, S.; Solanki, S. K.; Cameron, R. H.; Feller, A.;
   Pietarila, A.; Lagg, A.; Barthol, P.; Berkefeld, T.; Gandorfer, A.;
   Knoelker, M.; Martinez Pillet, V.; Schmidt, W.; Title, A.
Bibcode: 2012decs.confE..99J
Altcode:
  We analyze trajectories of the proper motion of intrinsically magnetic,
  isolated internetwork Ca II H BPs (with mean lifetime of 461 sec) to
  obtain their diffusivity behaviors. We use high spatial and temporal
  resolution image sequences of quiet-Sun, disc-centre observations
  obtained in the Ca II H 397 nm passband of the Sunrise Filter Imager
  (SuFI) on board the SUNRISE balloon-borne solar observatory. In
  order to avoid misidentification, the BPs are semi-manually selected
  and then automatically tracked. The trajectory of each BP is then
  calculated and its diffusion index is described by a power law
  exponent, using which we classify the BPs' trajectories into sub-,
  normal and super- diffusive. In addition, the corresponding diffusion
  coefficients (D) based on the observed displacements are consequently
  computed. We find a strong super-diffusivity at a height sampled by the
  SuFI/SUNRISE Ca II H passband (i.e. a height corresponding roughly to
  the temperature minimum). We find that 74% of the identified tiny BPs
  are super-diffusive, 18% move randomly (i.e. their motion corresponds
  to normal diffusion) and only 8% belong to the sub-diffusion regime. In
  addition, we find that 53% of the super-diffusion regime (i.e. 39% of
  all BPs) have the diffusivity index of 2 which are termed as "Ballistic
  BPs". Finally, we explore the distribution of diffusion index with the
  help of a simple simulation. The results suggest that the BPs are random
  walkers superposed by a systematic (background) velocity in which the
  magnitude of each component (and hence their ratio) depends on the time
  and spatial scales. We further discuss a simple sketch to explain the
  diffusivity of observed BPs while they migrate within a supergranule
  (i.e. internetwork areas) or close to the network regions.

Title: Siphon flow in a cool magnetic loop
Authors: Bethge, C.; Beck, C.; Peter, H.; Lagg, A.
Bibcode: 2012A&A...537A.130B
Altcode: 2011arXiv1111.5564B
  Context. Siphon flows that are driven by a gas pressure difference
  between two photospheric footpoints of different magnetic field strength
  connected by magnetic field lines are a well-studied phenomenon in
  theory, but observational evidence is scarce. Aims. We investigate the
  properties of a structure in the solar chromosphere in an active region
  to find out whether the feature is consistent with a siphon flow in
  a magnetic loop filled with chromospheric material. <P />Methods. We
  derived the line-of-sight (LOS) velocity of several photospheric
  spectral lines and two chromospheric spectral lines, Ca II H 3968.5
  *Aring; and He I 10830 Å, in spectropolarimetric observations of
  NOAA 10978 done with the Tenerife Infrared Polarimeter (TIP-II) and
  the POlarimetric LIttrow Spectrograph (POLIS). The structure can be
  clearly traced in the LOS velocity maps and the absorption depth of
  He I. The magnetic field configuration in the photosphere is inferred
  directly from the observed Stokes parameters and from inversions with
  the HELIX<SUP>+</SUP> code. Data from the full-disk Chromospheric
  Telescope (ChroTel) in He I in intensity and LOS velocity are used for
  tracking the temporal evolution of the flow, along with TRACE Fe IX/X
  171 Å data for additional information about coronal regions related to
  the structure under investigation. <P />Results. The inner end of the
  structure is located in the penumbra of a sunspot. It shows downflows
  whose strength decreases with decreasing height in the atmosphere. The
  flow velocity in He I falls abruptly from above 40 km s<SUP>-1</SUP>
  to about zero further into the penumbra. A slight increase of emission
  is seen in the Ca II H spectra at the endpoint. At the outer end of the
  structure, the photospheric lines that form higher up in the atmosphere
  show upflows that accelerate with height. The polarization signal near
  the outer end shows a polarity opposite to that of the sunspot, the
  magnetic field strength of 580 G is roughly half as large as at the
  inner end. The structure exists for about 90 min. Its appearance is
  preceeded by a brightening in its middle in the coronal TRACE data. <P
  />Conclusions. The observed flows match theoretical predictions of
  chromospheric and coronal siphon flows, with accelerating upflowing
  plasma at one footpoint with low field strength and decelerating
  downflowing plasma at the other end. A tube shock at the inner end is
  probable, but the evidence is not conclusive. The TRACE data suggest
  that the structure forms because of a reorganization of field lines
  after a reconnection event.

Title: Variation of quiet Sun magnetic elements between 2006 and
    2011 using Hinode SOT/SP
Authors: Buehler, D.; Lagg, A.; Solanki, S. K.
Bibcode: 2011sdmi.confE..76B
Altcode:
  The Hinode satellite has revealed copious amounts of horizontal flux
  covering the quiet Sun, nurturing the notion of local dynamo action
  operating close to the solar surface. We sought to investigate the
  variation in the occurrence as well as the strength of circular and
  linear polarisation on the quiet Sun during the minimum of cycle
  23, covering a period from November 2006 until August 2011. This
  investigation used Hinode SOT/SP images of the disk centre and a large
  FOV and focussed on line-integrated linear and circular polarisation
  signals obtained from the Fe I 6302.5 Å absorption line. The circular
  polarisation showed an overall linear decline in occurrence from
  November 2006 until August 2011. By comparing PDFs we found that
  this decline is associated in particular with network elements. The
  internetwork on the other hand showed a 10% decrease in occurrence
  from November 2010 until June 2009, followed by an equal increase
  until August 2011. The investigation also revealed a reduction of 30%
  in the occurrence of linear polarisation signals between November 2006
  and December 2009. From August 2010 until August 2011 the occurrence of
  linear polarisation was increasing again. Hence, our results show that
  the occurrence of the ubiquitous linear polarisation of the internetwork
  as seen by Hinode is measurably influenced by the solar cycle. This
  implies that an independent local dynamo process is unlikely to be
  the sole cause responsible for the generation of this magnetic flux.

Title: The Sun at high resolution: first results from the Sunrise
    mission
Authors: Solanki, S. K.; Barthol, P.; Danilovic, S.; Feller,
   A.; Gandorfer, A.; Hirzberger, J.; Lagg, A.; Riethmüller, T. L.;
   Schüssler, M.; Wiegelmann, T.; Bonet, J. A.; Pillet, V. Martínez;
   Khomenko, E.; del Toro Iniesta, J. C.; Domingo, V.; Palacios, J.;
   Knölker, M.; González, N. Bello; Borrero, J. M.; Berkefeld, T.;
   Franz, M.; Roth, M.; Schmidt, W.; Steiner, O.; Title, A. M.
Bibcode: 2011IAUS..273..226S
Altcode:
  The Sunrise balloon-borne solar observatory consists of a 1m aperture
  Gregory telescope, a UV filter imager, an imaging vector polarimeter,
  an image stabilization system and further infrastructure. The first
  science flight of Sunrise yielded high-quality data that reveal the
  structure, dynamics and evolution of solar convection, oscillations
  and magnetic fields at a resolution of around 100 km in the quiet
  Sun. Here we describe very briefly the mission and the first results
  obtained from the Sunrise data, which include a number of discoveries.

Title: The height of chromospheric loops in an emerging flux region
Authors: Merenda, L.; Lagg, A.; Solanki, S. K.
Bibcode: 2011A&A...532A..63M
Altcode: 2012arXiv1202.1113M
  Context. The chromospheric layer observable with the He i 10 830 Å
  triplet is strongly warped. The analysis of the magnetic morphology of
  this layer therefore requires a reliable technique to determine the
  height at which the He i absorption takes place. <BR /> Aims: The He
  i absorption signature connecting two pores of opposite polarity in an
  emerging flux region is investigated. This signature is suggestive of a
  loop system connecting the two pores. We aim to show that limits can be
  set on the height of this chromospheric loop system. <BR /> Methods: The
  increasing anisotropy in the illumination of a thin, magnetic structure
  intensifies the linear polarization signal observed in the He i triplet
  with height. This signal is altered by the Hanle effect. We apply an
  inversion technique incorporating the joint action of the Hanle and
  Zeeman effects, with the absorption layer height being one of the
  free parameters. <BR /> Results: The observed linear polarization
  signal can be explained only if the loop apex is higher than ≈ 5
  Mm. Best agreement with the observations is achieved for a height of
  6.3 Mm. <BR /> Conclusions: The strength of the linear polarization
  signal in the loop apex is inconsistent with the assumption of a He
  i absorption layer at a constant height level. The determined height
  supports the earlier conclusion that dark He 10 830 Å filaments in
  emerging flux regions trace emerging loops.

Title: Polarimetry with GREGOR
Authors: Balthasar, H.; Bello González, N.; Collados, M.; Denker,
   C.; Feller, A.; Hofmann, A.; Lagg, A.; Nagaruju, L.; Puschmann, K. G.;
   Soltau, D.; Volkmer, R.
Bibcode: 2011ASPC..437..351B
Altcode:
  A brief description of the new 1.5-meter solar telescope GREGOR located
  at the Observatorio del Teide in Tenerife will be given. GREGOR will
  provide a spatial resolution of about 75 km on the Sun, and with its
  light collecting capability we will be able to study the development
  of small magnetic features with high cadence. From the beginning,
  it will be equipped with the GREGOR Fabry-Pérot Interferometer
  (GFPI) for the visible spectral range and with a GRating Infrared
  Spectrograph (GRIS). Both postfocus instruments can be combined
  with a polarimeter, and in both cases the light is modulated by two
  ferro-electric liquid crystals. A calibration unit can be inserted to
  determine the instrumental polarization. Because of the altazimuthal
  mount, time-dependent rotation of the polarimetric reference plane
  is introduced, and we have to develop a polarization model of the
  telescope. Measurements to verify this model are in preparation.

Title: Intensity contrast from MHD simulations and HINODE observations
Authors: Afram, N.; Unruh, Y. C.; Solanki, S. K.; Schüssler, M.;
   Lagg, A.; Vögler, A.
Bibcode: 2011A&A...526A.120A
Altcode: 2010arXiv1011.6102A
  Context. Changes in the solar surface area, which is covered by
  small-scale magnetic elements, are thought to cause long-term changes
  in the solar spectral irradiance, which are important for determining
  the impact on Earth's climate. <BR /> Aims: To study the effect of
  small-scale magnetic elements on the total and spectral irradiance,
  we derive their contrasts from 3-D MHD simulations of the solar
  atmosphere. These calculations are necessary because measurements of
  small-scale flux tube contrasts are confined to a few wavelengths and
  affected by scattered light and instrument defocus, even for space
  observations. <BR /> Methods: To test the contrast calculations,
  we compare rms contrasts from simulations with those obtained with
  the broad-band filter imager mounted on the Solar Optical Telescope
  (SOT) onboard the Hinode satellite and also analyse centre-to-limb
  variations (CLV). The 3-D MHD simulations include the interaction
  between convection and magnetic flux tubes. They are performed by
  assuming non-grey radiative transfer and using the MURaM code. The
  simulations have an average vertical magnetic field of 0 G, 50 G, and
  200 G. Emergent intensities are calculated with the spectral synthesis
  code ATLAS9 and are convolved with a theoretical point-spread function
  to account for the properties of the observations' optical system. <BR
  /> Results: We find reasonable agreement between simulated and observed
  intensity distributions in the visible continuum bands. Agreement is
  poorer for the CN and G-bands. The analysis of the simulations uncovers
  a potentially more realistic centre-to-limb behaviour than calculations
  based on 1-D model atmospheres. <BR /> Conclusions: We conclude that
  starting from 3-D MHD simulations represents a powerful approach
  to obtaining intensity contrasts for a wide wavelength coverage and
  different positions across on the solar disk. This also paves the way
  for future calculations of facular and network contrast as a function
  of magnetic fluxes.

Title: Multicomponent He I 10 830 Å profiles in an active filament
Authors: Sasso, C.; Lagg, A.; Solanki, S. K.
Bibcode: 2011A&A...526A..42S
Altcode: 2011arXiv1101.5563S
  <BR /> Aims: We present new spectropolarimetric observations of the
  chromospheric He i 10 830 Å multiplet observed in a filament during
  its phase of activity. <BR /> Methods: The data were recorded with the
  new Tenerife Infrared Polarimeter (TIP-II) at the German Vacuum Tower
  Telescope (VTT) on 2005 May 18. We inverted the He Stokes profiles
  using multiple atmospheric components. <BR /> Results: The observed
  He Stokes profiles display a remarkably wide variety of shapes. Most
  of the profiles show very broad Stokes I absorptions and complex and
  spatially variable Stokes V signatures. The inversion of the profiles
  shows evidence of different atmospheric blue- and redshifted components
  of the He i lines within the resolution element (~1 arcsec), with
  supersonic velocities of up to ~100 km s<SUP>-1</SUP>. Up to five
  different atmospheric components are found in the same profile. We
  show that even these complex profiles can be reliably inverted.

Title: Fully Resolved Quiet-Sun Magnetic flux Tube Observed with
    the SUNRISE/IMAX Instrument
Authors: Lagg, A.; Solanki, S. K.; Riethmüller, T. L.; Martínez
   Pillet, V.; Schüssler, M.; Hirzberger, J.; Feller, A.; Borrero,
   J. M.; Schmidt, W.; del Toro Iniesta, J. C.; Bonet, J. A.; Barthol, P.;
   Berkefeld, T.; Domingo, V.; Gandorfer, A.; Knölker, M.; Title, A. M.
Bibcode: 2010ApJ...723L.164L
Altcode: 2010arXiv1009.0996L
  Until today, the small size of magnetic elements in quiet-Sun areas has
  required the application of indirect methods, such as the line-ratio
  technique or multi-component inversions, to infer their physical
  properties. A consistent match to the observed Stokes profiles could
  only be obtained by introducing a magnetic filling factor that specifies
  the fraction of the observed pixel filled with magnetic field. Here,
  we investigate the properties of a small magnetic patch in the quiet
  Sun observed with the IMaX magnetograph on board the balloon-borne
  telescope SUNRISE with unprecedented spatial resolution and low
  instrumental stray light. We apply an inversion technique based on
  the numerical solution of the radiative transfer equation to retrieve
  the temperature stratification and the field strength in the magnetic
  patch. The observations can be well reproduced with a one-component,
  fully magnetized atmosphere with a field strength exceeding 1 kG and
  a significantly enhanced temperature in the mid to upper photosphere
  with respect to its surroundings, consistent with semi-empirical flux
  tube models for plage regions. We therefore conclude that, within the
  framework of a simple atmospheric model, the IMaX measurements resolve
  the observed quiet-Sun flux tube.

Title: Magnetic structures of an emerging flux region in the solar
    photosphere and chromosphere
Authors: Xu, Z.; Lagg, A.; Solanki, S. K.
Bibcode: 2010A&A...520A..77X
Altcode:
  <BR /> Aims: We investigate the vector magnetic field and Doppler
  velocity in the photosphere and upper chromosphere of a young
  emerging flux region of the sun close to disk center. <BR /> Methods:
  Spectropolarimetric scans of a young active region made using the
  second generation Tenerife Infrared Polarimeter (TIP II) on the German
  Vacuum Tower Telescope (VTT) are analyzed. The scanned area contained
  multiple sunspots and an emerging flux region. An inversion based on
  the Milne-Eddington approximation was performed on the full Stokes
  vector of the chromospheric He I 10 830 Å and the photospheric Si I
  10 827.1 Å lines. This provided the magnetic vector and line-of-sight
  velocity at each spatial point in both atmospheric layers. <BR />
  Results: A clear difference is seen between the complex magnetic
  structure of the emerging flux region (EFR) in the photosphere and
  the much simpler structure in the upper chromosphere. The upper
  chromospheric structure is consistent with a set of emerging loops
  following elongated dark structures seen in the He I 10 830 Å triplet,
  similar to arch filament systems (AFS), while in the photosphere we
  infer the presence of U-loops within the emergence zone. Nonetheless, in
  general the upper chromospheric field has a similar linear relationship
  between inclination angle and field strength as the photospheric field:
  the field is weak (≈300 G) and horizontal in the emergence zone,
  but strong (up to 850 G) and more vertical near its edges. The field
  strength decreases from the photosphere to the upper chromosphere
  by approximately 0.1-0.2 G km<SUP>-1</SUP> (or even less) within the
  emergence zone and by 0.3-0.6 G km<SUP>-1</SUP> in sunspots located
  at its edge. We reconstructed the magnetic field in 3D based on the
  chromospheric vector field under the assumption that the He I 10 830 Å
  triplet forms along the magnetic field loops. The reconstructed loops
  are quite flat with supersonic downflows at both footpoints. Arguments
  and evidence for an enhanced formation height of He I 10 830 Å in
  arch-filaments seen in this line are provided, which support the
  validity of the reconstructed loops. <BR /> Conclusions: The main
  chromospheric properties of EFRs previously deduced for a single region
  NOAA 9451 are shown to be valid for another region as well, suggesting
  that the main original results may have a wider application. The main
  exception is that only the first region displayed a current sheet in
  the chromosphere. We propose a scenario in which the relatively complex
  photospheric structure evolves into the simpler chromospheric one.

Title: GREGOR telescope: start of commissioning
Authors: Volkmer, R.; von der Lühe, O.; Denker, C.; Solanki, S.;
   Balthasar, H.; Berkefeld, T.; Caligari, P.; Collados, M.; Halbgewachs,
   C.; Heidecke, F.; Hofmann, A.; Klvana, M.; Kneer, F.; Lagg, A.; Popow,
   E.; Schmidt, D.; Schmidt, W.; Sobotka, M.; Soltau, D.; Strassmeier, K.
Bibcode: 2010SPIE.7733E..0KV
Altcode: 2010SPIE.7733E..18V
  With the integration of a 1-meter Cesic primary mirror the GREGOR
  telescope pre-commissioning started. This is the first time, that
  the entire light path has seen sunlight. The pre-commissioning period
  includes testing of the main optics, adaptive optics, cooling system,
  and pointing system. This time was also used to install a near-infrared
  grating spectro-polarimeter and a 2D-spectropolarimeter for the visible
  range as first-light science instruments. As soon as the final 1.5
  meter primary mirror is installed, commissioning will be completed,
  and an extended phase of science verification will follow. In the near
  future, GREGOR will be equipped with a multi-conjugate adaptive optics
  system that is presently under development at KIS.

Title: GREGOR solar telescope: Design and status
Authors: Volkmer, R.; von der Lühe, O.; Denker, C.; Solanki, S. K.;
   Balthasar, H.; Berkefeld, T.; Caligari, P.; Collados, M.; Fischer, A.;
   Halbgewachs, C.; Heidecke, F.; Hofmann, A.; Klvaňa, M.; Kneer, F.;
   Lagg, A.; Popow, E.; Schmidt, D.; Schmidt, W.; Sobotka, M.; Soltau,
   D.; Strassmeier, K. G.
Bibcode: 2010AN....331..624V
Altcode:
  The integration and verification phase of the GREGOR telescope
  reached an important milestone with the installation of the
  interim 1 m SolarLite primary mirror. This was the first time
  that the entire light path had seen sunlight. Since then extensive
  testing of the telescope and its subsystems has been carried out. The
  integration and verification phase will culminate with the delivery and
  installation of the final 1.5 m Zerodur primary mirror in the summer of
  2010. Observatory level tests and science verification will commence in
  the second half of 2010 and in 2011. This phase includes testing of the
  main optics, adaptive optics, cooling and pointing systems. In addition,
  assuming the viewpoint of a typical user, various observational modes
  of the GREGOR Fabry-Pérot Interferometer (GFPI), the Grating Infrared
  Spectrograph (GRIS), and high-speed camera systems will be tested to
  evaluate if they match the expectations and science requirements. This
  ensures that GREGOR will provide high-quality observations with its
  combination of (multi-conjugate) adaptive optics and advanced post-focus
  instruments. Routine observations are expected for 2012.

Title: The calibration of the Cassini-Huygens CAPS Electron
    Spectrometer
Authors: Lewis, G. R.; Arridge, C. S.; Linder, D. R.; Gilbert, L. K.;
   Kataria, D. O.; Coates, A. J.; Persoon, A.; Collinson, G. A.; André,
   N.; Schippers, P.; Wahlund, J.; Morooka, M.; Jones, G. H.; Rymer,
   A. M.; Young, D. T.; Mitchell, D. G.; Lagg, A.; Livi, S. A.
Bibcode: 2010P&SS...58..427L
Altcode:
  We present the two-stage method used to calibrate the electron
  spectrometer (ELS), part of the plasma spectrometer (CAPS) on board
  the Cassini spacecraft currently in orbit around Saturn. The CAPS-ELS
  is a top-hat electrostatic analyser designed to measure electron
  fluxes between 0.5 eV and 26 keV. The on-ground calibration method
  described here includes the production of photoelectrons, which are
  energised and passed into the CAPS-ELS in a purpose designed calibration
  facility. Knowledge of the intensity of these incident electrons and
  the subsequent instrument output provides an on-ground calibrated
  geometric factor. Comparative studies of physical quantities such as
  plasma density and electron differential flux calculated using on-ground
  calibration factor with the quantities deduced from the wave experiment
  and high energy electron detector provide in-flight calibration. The
  results of this are presented together with a comparison of the
  experimentally calibrated values with simulated calibration values.

Title: Nonlinear force-free modelling: influence of inaccuracies in
    the measured magnetic vector
Authors: Wiegelmann, T.; Yelles Chaouche, L.; Solanki, S. K.; Lagg, A.
Bibcode: 2010A&A...511A...4W
Altcode: 2009arXiv0912.3002W
  Context. Solar magnetic fields are regularly extrapolated into the
  corona starting from photospheric magnetic measurements that can
  be affected by significant uncertainty. <BR /> Aims: We study how
  inaccuracies introduced into the maps of the photospheric magnetic
  vector by the inversion of ideal and noisy Stokes parameters influence
  the extrapolation of nonlinear force-free magnetic fields. <BR />
  Methods: We compute nonlinear force-free magnetic fields based on
  simulated vector magnetograms, by the inversion of Stokes profiles
  that were computed by a 3-D radiation MHD simulation snapshot. These
  extrapolations are compared with extrapolations that originate directly
  in the field in the MHD simulations, which is our reference. We
  investigate how line formation and instrumental effects such as noise,
  limited spatial resolution, and the effect of employing a filter
  instrument influence the resulting magnetic field structure. The
  comparison is performed qualitatively by visually inspecting the
  magnetic field distribution and quantitatively by different metrics. <BR
  /> Results: The reconstructed field is most accurate if ideal Stokes
  data are inverted and becomes less accurate if instrumental effects
  and noise are included. The results demonstrate that the nonlinear
  force-free field extrapolation method tested here is relatively
  insensitive to the effects of noise in measured polarization spectra
  at levels consistent with present-day instruments. <BR /> Conclusions:
  Our results show that we can reconstruct the coronal magnetic field as
  a nonlinear force-free field from realistic photospheric measurements
  with an accuracy of a few percent, at least in the absence of sunspots.

Title: Temperatures of small scale magnetic structures in deep solar
    photospheric layers
Authors: Oklay, Nilda; Gandorfer, Achim; Lagg, Andreas; Solanki,
   Sami K.; Bianda, Michele; Ramelli, Renzo
Bibcode: 2010cosp...38.2857O
Altcode: 2010cosp.meet.2857O
  With current solar instrumentation, small scale magnetic
  structures still remain unresolved. Nevertheless, it is possible
  to retrieve information about these unresolved magnetic structures
  via spectropolarimetry. For this reason, IRSOL (Istituto Ricerche
  Solari Locarno) facility is used to obtain simultaneously recorded
  spectra of Stokes I and Stokes V/I of CI (5380.3 A), FeI (5379.6 A,
  5383.4 A) and TiII (5381.0 A) lines on an active region using the
  ZIMPOL II (Zurich Imaging Polarimeter II) instrument. We used Stokes V
  amplitude ratios technique to investigate temperatures of unresolved
  magnetic features down to deep photospheric layers. Atmospheric
  parameters are obtained from the inversions done with the SPINOR code
  (Stokes-Profile-INversion-O-Routines). Then the results are compared
  with the results from the realistic MHD simulations obtained from
  MURaM code (MPS/University of Chicago radiative MHD). Comparisons of
  the results from observations, inversions and numerical simulations
  show a good agreement, which confirms the usage of this technique as
  a temperature diagnostic tool.

Title: How do inaccuracies and unresolved structures in the measured
    solar photospheric magnetic vector influence the accuracy of coronal
    magnetic field models?
Authors: Wiegelmann, Thomas; Yelles, Lotfi; Solanki, Sami; Lagg,
   Andreas
Bibcode: 2010cosp...38.2827W
Altcode: 2010cosp.meet.2827W
  Solar magnetic fields are usually extrapolated into the corona
  starting from photospheric mag-netic measurements that can suffer from
  significant uncertainties caused by the presence of unresolved fine
  structures due to a limited spatial resolution and by the limited
  polarimet-ric accuracy and spectral resolution. We investigate
  how these inaccuracies in the measured photospheric magnetic field
  vector influence the accuracy of the extrapolated coronal mag-netic
  field. We compare non-linear force-free coronal magnetic field
  extrapolations from a 3-D radiation MHD simulation snapshot with
  corresponding extrapolations from synthetic vector magnetograms. The
  synthetic magnetograms contain instrumental effects such as noise,
  limited spatial and spectral resolution and the effect of employing a
  filter instrument. The parameters are chosen in particular to mimic the
  effects of the Hinode/SOT and the future Solar Orbiter PHI instruments,
  respectively. We discuss, how photospheric structures, which are
  inherent in the MHD snapshot, but not resolved in the photospheric
  magnetic field measurements, influence the quality of the computed
  coronal magnetic field model.

Title: Relation between the Sunrise photospheric magnetic field and
    the Ca II H bright features
Authors: Jafarzadeh, Shahin; Hirzberger, J.; Feller, A.; Lagg, A.;
   Solanki, S. K.; Pietarila, A.; Danilovic, S.; Riethmueller, T.;
   Barthol, P.; Berkefeld, T.; Gandorfer, A.; Knülker, M.; Martínez
   Pillet, V.; Schmidt, W.; Schüssler, M.; Title, A.
Bibcode: 2010cosp...38.2856J
Altcode: 2010cosp.meet.2856J
  Recent observations from the Sunrise balloon-borne solar telescope
  have enabled us to reach an unprecedented high spatial resolution
  on the solar surface with the near-ultraviolet photo-spheric and
  chromospheric images as well as the magnetograms. We use these high
  resolution observations to investigate the structure of the solar
  upper photosphere and lower chromosphere as well as their temporal
  evolutions. We study the relation between the inter-granular Ca II
  397 nm bright structures in images obtained by the Sunrise Filter
  Imager (SuFI) and their corresponding photospheric vector magnetic
  field computed from the Imaging Magnetogram eXperiment (IMaX)
  observations. The targets under study are in a quiet Sun region and
  close to disc-centre.

Title: Energetic particles in Saturn's magnetosphere during the
    Cassini nominal mission (July 2004-July 2008)
Authors: Krupp, N.; Roussos, E.; Lagg, A.; Woch, J.; Müller, A. L.;
   Krimigis, S. M.; Mitchell, D. G.; Roelof, E. C.; Paranicas, C.;
   Carbary, J.; Jones, G. H.; Hamilton, D. C.; Livi, S.; Armstrong,
   T. P.; Dougherty, M. K.; Sergis, N.
Bibcode: 2009P&SS...57.1754K
Altcode:
  In July 2004 the Cassini spacecraft began its orbital tour in the
  Saturnian system and performed 74 orbits during the nominal mission
  (July 2004-July 2008) providing data from nearly all local times at
  various distances and latitudes relative to the planet. The particles
  and field instruments onboard the spacecraft were essentially operating
  continuously offering the possibility to study the global configuration
  and the dynamics of the second largest magnetosphere in our solar
  system extensively. One of those instruments aboard Cassini is the Low
  Energy Magnetospheric Measurement System (LEMMS), one of three particle
  detectors of the Magnetospheric Imaging Instrument (MIMI). MIMI/LEMMS
  measures the intensity, energy spectra and pitch angle distributions of
  energetic ions (E&gt;30keV) and electrons (E&gt;20keV) separately. The
  measured energetic particle distributions together with the measured
  magnetic field provide a very powerful tool to investigate the
  Saturnian magnetosphere in those regions covered by the Cassini
  orbits. This paper will give an overview of the energetic particle
  measurements of the MIMI/LEMMS sensor in the Saturnian system. In the
  first part of the paper synoptic maps will be shown where all the data
  are presented as a function of various trajectory parameters of the
  spacecraft. Secondly bi-directional electron distributions along the
  magnetic field direction will be described as a feature in the Saturnian
  system. Thirdly the particle parameters in the inner magnetosphere with
  absorption signatures of the various moons are presented. Fourthly it
  will be shown that the region around about 15 R<SUB>S</SUB> seems to
  be a characteristic region where depletion signatures in energetic
  particle distributions are very often observed. At the end of this
  work a 60 min intensity periodicity in the MIMI/LEMMS data is discussed.

Title: Simulation of a flux emergence event and comparison with
    observations by Hinode
Authors: Yelles Chaouche, L.; Cheung, M. C. M.; Solanki, S. K.;
   Schüssler, M.; Lagg, A.
Bibcode: 2009A&A...507L..53Y
Altcode: 2009arXiv0910.5737Y
  Aims: We study the observational signature of flux emergence in
  the photosphere using synthetic data from a 3D MHD simulation of the
  emergence of a twisted flux tube. <BR />Methods: Several stages in the
  emergence process are considered. At every stage we compute synthetic
  Stokes spectra of the two iron lines Fe I 6301.5 Å and Fe I 6302.5
  Å and degrade the data to the spatial and spectral resolution of
  Hinode's SOT/SP. Then, following observational practice, we apply
  Milne-Eddington-type inversions to the synthetic spectra in order
  to retrieve various atmospheric parameters and compare the results
  with recent Hinode observations. <BR />Results: During the emergence
  sequence, the spectral lines sample different parts of the rising
  flux tube, revealing its twisted structure. The horizontal component
  of the magnetic field retrieved from the simulations is close to the
  observed values. The flattening of the flux tube in the photosphere is
  caused by radiative cooling, which slows down the ascent of the tube
  to the upper solar atmosphere. Consistent with the observations, the
  rising magnetized plasma produces a blue shift of the spectral lines
  during a large part of the emergence sequence. <P />Figure 3 is only
  available in electronic form at http://www.aanda.org

Title: Internetwork Horizontal Magnetic Fields in the Quiet Sun
Chromosphere: Results from a Joint Hinode/VTT Study
Authors: Lagg, A.; Ishikawa, R.; Merenda, L.; Wiegelmann, T.; Tsuneta,
   S.; Solanki, S. K.
Bibcode: 2009ASPC..415..327L
Altcode:
  We present results from a joint Hinode/VTT campaign (May
  2008). Spectropolarimetric data of a quiet Sun super-granular network
  cell at a heliocentric angle of 28° in the He I 10830 Å line were
  analyzed using an inversion code incorporating Hanle and Zeeman effects
  (HeLIx^+) to retrieve magnetic field strength and direction in the upper
  chromosphere. Simultaneously recorded Hinode SOT/SP data reveal the
  photospheric magnetic field morphology, clearly showing magnetic flux
  concentrations in the internetwork. The photospheric magnetic field
  maps are used to feed potential field extrapolations similar to the
  work by Schrijver &amp; Title (2003). The extrapolated magnetic field
  structure is compared with the magnetic field configuration resulting
  from the He 10830 inversions. These inversions also reveal horizontal
  magnetic structures extending over a length of up to 20 Mm above the
  internetwork, indicative of the presence of a magnetic canopy. The
  photospheric magnetic flux concentrations in the internetwork are
  obviously not sufficiently strong to prevent the formation of a canopy
  at chromospheric heights.

Title: High-resolution spectro-polarimetry of a flaring sunspot
    penumbra
Authors: Hirzberger, J.; Riethmüller, T.; Lagg, A.; Solanki, S. K.;
   Kobel, P.
Bibcode: 2009A&A...505..771H
Altcode: 2009arXiv0908.3803H
  We present simultaneous photospheric and chromospheric observations
  of the trailing sunspot in NOAA 10904 during a weak flare eruption
  (GOES magnitude B7.8), obtained with the Swedish Solar Telescope
  (SST) in La Palma, Canary Islands. High-resolution Ca II H images
  show a typical two-ribbon structure that has been hitherto only
  known for larger flares, and the flare appears in a confined region
  that is discernible by a bright border. The underlying photosphere
  shows a disturbed penumbral structure with intersecting branches of
  penumbral filaments. High-resolution Doppler- and vector-magnetograms
  exhibit oppositely directed Evershed flows and magnetic field vectors
  in the individual penumbral branches, resulting in several regions
  of magnetic azimuth discontinuity and several islands where the
  vertical magnetic field is reversed. The discontinuity regions are
  co-spatial with the locations of the onset of the flare ribbons. From
  the results, we conclude that the confined flare region is detached
  from the global magnetic field structure by a separatrix marked by the
  bright border visible in C II H. We further conclude that the islands
  of reversed vertical field appear because of flux emergence and that
  the strong magnetic shear appearing in the regions of magnetic azimuth
  discontinuity triggers the flare. <P />Movies are only available in
  electronic form at http://www.aanda.org

Title: Full Magnetic Field Vector of an Emerging Flux Region
Authors: Xu, Z.; Lagg, A.; Solanki, S. K.
Bibcode: 2009ASPC..405..223X
Altcode:
  We present maps of the full magnetic field vector of an emerging flux
  region in both the photosphere and chromosphere. The magnetic and
  velocity structure of freshly emerged loops is determined.

Title: A summary of observational records on periodicities above
    the rotational period in the Jovian magnetosphere
Authors: Kronberg, E. A.; Woch, J.; Krupp, N.; Lagg, A.
Bibcode: 2009AnGeo..27.2565K
Altcode:
  The Jovian magnetosphere is a very dynamic system. The plasma
  mass-loading from the moon Io and the fast planetary rotation lead
  to regular release of mass from the Jovian magnetosphere and to
  a change of the magnetic topology. These regular variations, most
  commonly on several (2.5-4) days scale, were derived from various
  data sets obtained by different spacecraft missions and instruments
  ranging from auroral images to in situ measurements of magnetospheric
  particles. Specifically, ion measurements from the Galileo spacecraft
  represent the periodicities, very distinctively, namely the
  periodic thinning of the plasma sheet and subsequent dipolarization,
  and explosive mass release occurring mainly during the transition
  between these two phases. We present a review of these periodicities,
  particularly concentrating on those observed in energetic particle
  data. The most distinct periodicities are observed for ions of sulfur
  and oxygen. The periodic topological change of the Jovian magnetosphere,
  the associated mass-release process and auroral signatures can be
  interpreted as a global magnetospheric instability with analogies to
  the two step concept of terrestrial substorms. Different views on the
  triggering mechanism of this magnetospheric instability are discussed.

Title: The Three-Dimensional Structure of Magnetic Fields and Electric
    Currents in an Active Region
Authors: Deng, Na; Choudhary, D.; Lagg, A.; Jing, J.; Wang, H.
Bibcode: 2009SPD....40.0904D
Altcode:
  Active Region NOAA 9661 consisting of various magnetic features (alpha
  spot, delta spot, pores, and plages) was observed simultaneously
  in three spectral lines (FeI 630.25, 630.15, and MgI 517.27) using
  full Stokes spectro-polarimetry with Advanced Stokes Polarimeter at
  NSO/SP. The formation heights of the three spectral lines span from
  photosphere to the low chromosphere. The magnetic field vectors are
  inverted from Stokes parameters using advanced inversion codes. In
  particular, HeLIx code is used to invert MgI's observation because
  it is dedicated for chromospheric Stokes inversion. The inverted
  magnetic field vectors in multiple atmospheric layers enable us to
  derive the three dimensional structure of the magnetic fields, electric
  current densities, current helicities, and their height gradients. <P
  />Acknowledgments: <P />This work is supported by NASA under grants
  NNX08AQ32G and NNX08AQ89G, and by NSF under grants ATM 05-48952 and
  ATM 07-16950.

Title: Coupling from the Photosphere to the Chromosphere and the
    Corona
Authors: Wedemeyer-Böhm, S.; Lagg, A.; Nordlund, Å.
Bibcode: 2009SSRv..144..317W
Altcode: 2008SSRv..tmp..171W; 2008arXiv0809.0987W
  The atmosphere of the Sun is characterized by a complex interplay of
  competing physical processes: convection, radiation, conduction, and
  magnetic fields. The most obvious imprint of the solar convection
  and its overshooting in the low atmosphere is the granulation
  pattern. Beside this dominating scale there is a more or less smooth
  distribution of spatial scales, both towards smaller and larger
  scales, making the Sun essentially a multi-scale object. Convection and
  overshooting give the photosphere its face but also act as drivers for
  the layers above, namely the chromosphere and corona. The magnetic field
  configuration effectively couples the atmospheric layers on a multitude
  of spatial scales, for instance in the form of loops that are anchored
  in the convection zone and continue through the atmosphere up into
  the chromosphere and corona. The magnetic field is also an important
  structuring agent for the small, granulation-size scales, although
  (hydrodynamic) shock waves also play an important role—especially in
  the internetwork atmosphere where mostly weak fields prevail. Based on
  recent results from observations and numerical simulations, we attempt
  to present a comprehensive picture of the atmosphere of the quiet Sun
  as a highly intermittent and dynamic system.

Title: Zeeman Broadening in Cool Stars
Authors: Anderson, Richard I.; Reiners, Ansgar; Solanki, Sami K.;
   Lagg, Andreas
Bibcode: 2009AIPC.1094..708A
Altcode: 2009csss...15..708A
  We investigate detectability of magnetic fields by Zeeman broadening
  of well-isolated spectral lines in F, G and K type stars. Data of
  unprecedented quality were taken with CES<SUP>1</SUP> mounted on the 3.6
  m ESO telescope at La Silla, Chile, in three campaigns in the optical
  range between 5770 Å and 6280 Å, each with a wavelength coverage
  of roughly 40 Å. We use the SPINOR/STOPRO (cf. Frutiger et al. [1])
  package developed by ETH<SUP>2</SUP> and MPS<SUP>3</SUP> to perform
  spectral line inversion via χ<SUP>2</SUP> minimization. Starting from
  constraints given by previous measurements of stellar parameters,
  we fit a number of extracted spectral lines. Eventually, our goal
  is to determine the product of the magnetic field strength B and the
  surface filling factor, B×f. <P />Our work is in progress and thus
  no final measurements can be presented at this stage.

Title: Coupling from the Photosphere to the Chromosphere and the
    Corona
Authors: Wedemeyer-Böhm, S.; Lagg, A.; Nordlund, Å.
Bibcode: 2009odsm.book..317W
Altcode:
  The atmosphere of the Sun is characterized by a complex interplay of
  competing physical processes: convection, radiation, conduction, and
  magnetic fields. The most obvious imprint of the solar convection
  and its overshooting in the low atmosphere is the granulation
  pattern. Beside this dominating scale there is a more or less smooth
  distribution of spatial scales, both towards smaller and larger
  scales, making the Sun essentially a multi-scale object. Convection and
  overshooting give the photosphere its face but also act as drivers for
  the layers above, namely the chromosphere and corona. The magnetic field
  configuration effectively couples the atmospheric layers on a multitude
  of spatial scales, for instance in the form of loops that are anchored
  in the convection zone and continue through the atmosphere up into
  the chromosphere and corona. The magnetic field is also an important
  structuring agent for the small, granulation-size scales, although
  (hydrodynamic) shock waves also play an important role—especially in
  the internetwork atmosphere where mostly weak fields prevail. Based on
  recent results from observations and numerical simulations, we attempt
  to present a comprehensive picture of the atmosphere of the quiet Sun
  as a highly intermittent and dynamic system.

Title: CRISP Spectropolarimetric Imaging of Penumbral Fine Structure
Authors: Scharmer, G. B.; Narayan, G.; Hillberg, T.; de la Cruz
   Rodriguez, J.; Löfdahl, M. G.; Kiselman, D.; Sütterlin, P.; van
   Noort, M.; Lagg, A.
Bibcode: 2008ApJ...689L..69S
Altcode: 2008arXiv0806.1638S
  We discuss penumbral fine structure in a small part of a pore,
  observed with the CRISP imaging spectropolarimeter at the Swedish
  1-m Solar Telescope (SST), close to its diffraction limit of
  0.16''. Milne-Eddington inversions applied to these Stokes data
  reveal large variations of field strength and inclination angle over
  dark-cored penumbral intrusions and a dark-cored light bridge. The
  mid-outer part of this penumbra structure shows ~0.3'' wide spines,
  separated by ~1.6'' (1200 km) and associated with 30° inclination
  variations. Between these spines, there are no small-scale magnetic
  structures that easily can be identified with individual flux tubes. A
  structure with nearly 10° more vertical and weaker magnetic field is
  seen midway between two spines. This structure is cospatial with the
  brightest penumbral filament, possibly indicating the location of a
  convective upflow from below.

Title: Mass release process in the Jovian magnetosphere: Statistics
    on particle burst parameters
Authors: Kronberg, E. A.; Woch, J.; Krupp, N.; Lagg, A.
Bibcode: 2008JGRA..11310202K
Altcode:
  The Jovian magnetosphere undergoes periodic reconfiguration processes
  mainly driven by the fast planetary rotation and mass loading from the
  moon Io. These reconfiguration processes of the Jovian magnetosphere
  are associated with the release of plasmoids discernible as ion flow
  bursts associated with bipolar magnetic signatures. We investigate
  these plasma flows statistically using data from the Energetic Particles
  Detector and from the magnetometer on board Galileo. The plasma flows
  are observed in different magnetospheric regions: the current sheet
  center, the plasma sheet boundary layers, and the lobe. We show that
  the bulk velocity of all species is the same for most of the magnetic
  field bipolar signatures associated with these plasma flows. The average
  speed of the observed plasmoids in the plasma sheet associated with
  the ion flow bursts is between 350 and 500 km s<SUP>-1</SUP>, and
  the duration of the events is between 10 and 20 min. The associated
  plasmoid length is correspondingly ∼9 R<SUB>J</SUB>. The plasmoids
  are moving approximately with Alfvénic speed. The convection electric
  field during the plasmoid release is about an order of magnitude higher
  than the ambient value of the Jovian convection electric field.

Title: Loop Morphology and Flows and their Relation to the Magnetic
    Field
Authors: Teriaca, L.; Wiegelmann, T.; Lagg, A.; Solanki, S. K.; Curdt,
   W.; Sekii, T.
Bibcode: 2008ASPC..397..196T
Altcode:
  In November 2006 we obtained several rasters of a large sunspot
  and its trailing region using the SUMER spectrometer on SOHO. The
  observations consist of spectroheliograms in the continuum around
  142 nm and in several spectral lines formed between 80000 K and
  0.6 MK, covering the temperature range from the chromosphere to
  the lower corona. The observed profiles provide LOS velocity and
  Doppler width maps. TRACE images in the EUV passbands and in the 160
  nm continuum provide a clear picture of the coronal loops and the
  chromosphere near their footpoints. The same target was also observed
  by all the instruments aboard Hinode and, in particular, by the SOT
  spectro-polarimeter measuring the photospheric magnetic vector. We
  combined SOT and MDI data (covering a larger FOV) to infer the coronal
  magnetic field of the active region by a nonlinear force-free field
  extrapolation. The observed radiance and velocity patterns at the
  various heights/temperatures throughout the solar atmosphere are
  compared with the field topology.

Title: The Magnetic Vector Structure of an Active Region Plage Field
Authors: Meling, M. H. M.; Lagg, A.; Solanki, S. K.
Bibcode: 2008ESPM...12.2.58M
Altcode:
  We present scans of the active region plage associated with NOAA 10953,
  recorded with the Tenerife Infrared Polarimeter 2 (TIP-2) mounted
  behind the German Vacuum Tower Telescope (VTT) on Tenerife and the
  SOT-SP instrument on-board the HINODE spacecraft. TIP-2 recorded the
  full Stokes vector close to the diffraction limit of the telescope over
  a 20 angstroem wavelength range containing six magnetically sensitive
  FeI lines in the infrared including the g=3 line FeI 15648.5. With
  these lines we use the advantage that the Zeeman splitting dominates
  over the Doppler broadening for kG fields. The iron lines used by
  HINODE are FeI 6301.501and FeI 6302.494. <P />We analyzed the data by
  applying a Milne-Eddington type inversion to it. In the context of a
  two-component model we found a bimodal distribution of field strengths,
  strong fields whose field strength distribution peaks at 1400 [G]
  and a weak field distribution, which may be associated with quiet sun
  regions bordering on the plage.

Title: SST/CRISP Magnetometry with Fe I 630.2 nm
Authors: Narayan, G.; Scharmer, G. B.; Hillberg, T.; Lofdahl, M.;
   van Noort, M.; Sutterlin, P.; Lagg, A.
Bibcode: 2008ESPM...122.120N
Altcode:
  We present recent full Stokes observations in the Fe I 630.2 nm
  line with CRISP, an imaging spectropolarimeter at the Swedish 1-m
  Solar Telescope (SST). The observations reach a spatial resolution
  of 0".16, close to the diffraction limit of the SST, representing
  a major improvement over any past ground based or space based
  spectropolarimetric data. We describe the data acquisition and reduction
  methods and present results of Milne-Eddington(ME) inversions applied
  on observations of plage.

Title: Magnetic Structure of a Filament during its Phase of Activity
Authors: Sasso, C.; Lagg, A.; Solanki, S. K.
Bibcode: 2008ESPM...12.2.19S
Altcode:
  We analyze and interpret spectropolarimetric observations of an active
  region filament located close to the solar disc center, during its
  phase of activity. The observations are obtained in the chromospheric
  He I lines at 1083.0 nm. We provide novel observational results on the
  magnetic field measurements in solar filaments to give constraints
  to the theoretical models of their support in the solar corona. Our
  main goal is to interpret the behavior of the atmospheric parameters
  retrieved from the spectropolarimetric data to give a picture of
  the magnetic structure of the observed filament. The analysis of the
  observed polarization of the He I 1083.0 nm multiplet in the filament,
  carried out by inverting the Stokes profiles, reveals the presence of
  different unresolved atmospheric components of the He lines, coexisting
  within the resolution element (1.2 arcsec). The different components,
  belonging to different magnetic field lines, show supersonic up-
  and downflows, sometimes within the same resolution element. The He
  blueshifted components belong to mostly transversal field lines in
  the body of the filament. These field lines are found to be curving
  upwards on both sides. This picture suggests the presence of dipped
  field lines that are moving upward, carrying with them the filament
  material. During this movement, we also observe filament material
  flowing down along field lines having the same polarity as the
  photospheric field (i.e. they have the opposite inclination with
  respect to the dipped field lines). These downflows are faster at the
  filament end points and can reach values close to 10 times the speed of
  sound. The field lines are found to be almost parallel to the filament
  axis in the plane perpendicular to the line of sight. We use the two
  main theoretical models of prominence support (dip or flux rope models)
  to interpret the results obtained.

Title: The intensity contrast of solar granulation: comparing Hinode
    SP results with MHD simulations
Authors: Danilovic, S.; Gandorfer, A.; Lagg, A.; Schüssler, M.;
   Solanki, S. K.; Vögler, A.; Katsukawa, Y.; Tsuneta, S.
Bibcode: 2008A&A...484L..17D
Altcode: 2008arXiv0804.4230D
  Context: The contrast of granulation is an important quantity
  characterizing solar surface convection. <BR />Aims: We compare the
  intensity contrast at 630 nm, observed using the Spectro-Polarimeter
  (SP) aboard the Hinode satellite, with the 3D radiative MHD simulations
  of Vögler &amp; Schüssler (2007, A&amp;A, 465, L43). <BR />Methods:
  A synthetic image from the simulation is degraded using a theoretical
  point-spread function of the optical system, and by considering other
  important effects. <BR />Results: The telescope aperture and the
  obscuration by the secondary mirror and its attachment spider, reduce
  the simulated contrast from 14.4% to 8.5%. A slight effective defocus
  of the instrument brings the simulated contrast down to 7.5%, close to
  the observed value of 7.0%. <BR />Conclusions: A proper consideration
  of the effects of the optical system and a slight defocus, lead to
  sufficient degradation of the synthetic image from the MHD simulation,
  such that the contrast reaches almost the observed value. The remaining
  small discrepancy can be ascribed to straylight and slight imperfections
  of the instrument, which are difficult to model. Hence, Hinode SP data
  are consistent with a granulation contrast which is predicted by 3D
  radiation MHD simulations.

Title: Multiheight Analysis of Asymmetric Stokes Profiles in a Solar
    Active Region
Authors: Deng, N.; Choudhary, D.; Solanki, S. K.; Lagg, A.
Bibcode: 2008AGUSMSP51D..06D
Altcode:
  Parameters characterizing Stokes asymmetries are derived from full
  Stokes I,Q,U,V spectra of FeI λλ 630.15, 630.25~nm line pair
  (formed at two different heights in the photosphere) and MgI b
  517.27~nm line (formed at lower chromosphere) in a solar active
  region near disc center. The spectropolarimetric observations were
  taken with the National Solar Observatory/High Altitude Observatory
  Advanced Stokes Polarimeter. The observed active region consists
  of a α sunspot, a δ sunspot, several pores and granulation. The
  line center shifts and bi-sectors derived from Stokes-I profiles
  describe the line-of-sight Doppler velocity and Stokes-I asymmetry,
  respectively. Stokes-V amplitude and area asymmetries are defined by
  the normalized difference of respective quantities between blue and
  red lobes of circular polarization profiles. The same can be derived
  from linear polarization profiles ([Q2+U2]1/2). The Stokes asymmetries
  are compared for different regions and at multiple heights. Neutral
  line regions of the δ spot and outer penumbral regions show distinct
  large Stokes asymmetries. Both Stokes-V amplitude and area asymmetries
  become larger from lower to higher atmosphere in neutral line regions
  that have strong transverse field and mixed polarities. The Stokes-V
  area asymmetry of outer edge of penumbrae changes from positive in
  the photosphere to negative in lower chromosphere. Detailed results
  and interpretation will be presented.

Title: The nature of running penumbral waves revealed
Authors: Bloomfield, D. S.; Lagg, A.; Solanki, S. K.
Bibcode: 2008IAUS..247...55B
Altcode: 2007IAUS..247...55B
  We seek to clarify the nature of running penumbral (RP) waves:
  are they chromospheric trans-sunspot waves or a visual pattern of
  upward-propagating waves? Full Stokes spectropolarimetric time series
  of the photospheric Sii10827 Å line and the chromospheric Hei10830 Å
  multiplet were inverted using a Milne-Eddington code. Spatial pixels
  were paired between the outer umbral/inner penumbral photosphere
  and the penumbral chromosphere using inclinations retrieved by the
  inversion and the dual-height pairings of line-of-sight velocity time
  series were studied for signatures of wave propagation using a Fourier
  phase difference analysis. The dispersion relation for radiatively
  cooling acoustic waves, modified to incorporate an inclined propagation
  direction, fits well the observed phase differences between the pairs
  of photospheric and chromospheric pixels. We have thus demonstrated
  that RP waves are in effect low-β slow-mode waves propagating along
  the magnetic field.

Title: Stratification of Sunspot Umbral Dots from Inversion of Stokes
    Profiles Recorded by Hinode
Authors: Riethmüller, T. L.; Solanki, S. K.; Lagg, A.
Bibcode: 2008ApJ...678L.157R
Altcode: 2008arXiv0805.4324R
  This work aims to constrain the physical nature of umbral dots (UDs)
  using high-resolution spectropolarimetry. Full Stokes spectra recorded
  by the spectropolarimeter on Hinode of 51 UDs in a sunspot close to the
  disk center are analyzed. The height dependence of the temperature,
  magnetic field vector, and line-of-sight velocity across each UD
  is obtained from an inversion of the Stokes vectors of the two Fe I
  lines at 630 nm. No difference is found at higher altitudes [-3 &lt;=
  log (τ<SUB>500</SUB>) &lt;= - 2] between the UDs and the diffuse
  umbral background. Below that level the difference rapidly increases,
  so that at the continuum formation level [log (τ<SUB>500</SUB>) = 0]
  we find on average a temperature enhancement of 570 K, a magnetic field
  weakening of 510 G, and upflows of 800 m s<SUP>-1</SUP> for peripheral
  UDs, whereas central UDs display an excess temperature of on average
  550 K, a field weakening of 480 G, and no significant upflows. The
  results for, in particular, the peripheral UDs, including cuts of
  magnetic vector and velocity through them, look remarkably similar to
  the output of recent radiation MHD simulations. They strongly suggest
  that UDs are produced by convective upwellings.

Title: The FeH F<SUP>4</SUP>Δ-X<SUP>4</SUP>Δ system. Creating a
    valuable diagnostic tool to explore solar and stellar magnetic fields
Authors: Afram, N.; Berdyugina, S. V.; Fluri, D. M.; Solanki, S. K.;
   Lagg, A.
Bibcode: 2008A&A...482..387A
Altcode:
  Context: Lines of diatomic molecules are ideal tools for studying
  cool stellar atmospheres and the internal structure of sunspots
  and starspots, given their temperature and pressure sensitivities,
  which are typically higher than in atomic lines. The Wing-Ford FeH
  F<SUP>4</SUP>Δ-X<SUP>4</SUP>Δ system represents such a diatomic
  molecule that is, in addition, highly sensitive to magnetic fields. The
  current theoretical description of those transitions that include the
  involved molecular constants, however, are only based on intensity
  measurements because polarimetric observations have not been available
  until now, which limits their diagnostic value. Furthermore, the theory
  has so far been optimized to reproduce energy levels and line strengths
  without taking magnetic sensitivities into account. <BR />Aims: The
  FeH F<SUP>4</SUP>Δ-X<SUP>4</SUP>Δ system is produced by transitions
  between two electronic states with the coupling of the angular momenta
  that is intermediate between limiting Hund's cases (a) and (b). Our goal
  is to investigate the diagnostic capabilities of the current theoretical
  description of the molecule FeH. <BR />Methods: Using the most precise
  available Hamiltonian, we carried out the perturbation calculation
  of the molecular Zeeman effect for this transition and computed the
  Landé factors of the energy levels and of transitions. We extracted
  Landé factors from a comparison of observed and calculated Stokes
  I and V profiles. Certain spectral lines, most frequently with high
  magnetic sensitivity, exhibited discrepancies between the theory and
  observations. We extended the theoretical model with a semi-empirical
  approach to obtain a diagnostic tool that is able to reproduce many
  of the interesting spectral lines. <BR />Results: We find that the
  current theory successfully reproduces the magnetic properties of
  a large number of lines in the FeH F<SUP>4</SUP>Δ-X<SUP>4</SUP>Δ
  system and that the modified Hamiltonian allows us to synthesize
  and successfully reproduce the most sensitive lines. Thus, our
  observations have provided valuable constraints for determining
  empirical molecular constants and Landé factors. <BR />Conclusions:
  The FeH F<SUP>4</SUP>Δ-X<SUP>4</SUP>Δ system is found to be a very
  sensitive magnetic diagnostic tool. Polarimetric data of these lines,
  in contrast to intensity measurements, provide us with more direct
  and detailed information to study the coolest parts of sunspot and
  starspot umbrae, as well as cool active dwarfs.

Title: Comparison of periodic substorms at Jupiter and Earth
Authors: Kronberg, E. A.; Woch, J.; Krupp, N.; Lagg, A.; Daly, P. W.;
   Korth, A.
Bibcode: 2008JGRA..113.4212K
Altcode:
  The Energetic Particles Detector and magnetometer measurements on
  Galileo showed that the Jovian magnetosphere undergoes reconfiguration
  processes which are very similar to the characteristics of a
  terrestrial substorm. At Jupiter the reconfiguration process occurs
  quasi-periodically with a repetition period of several days. In
  the terrestrial magnetosphere periodic substorms have been observed
  during magnetic storms. The comparison of the periodic magnetospheric
  disturbances at Jupiter and Earth shows that they are similar in dynamic
  features as well as in spatial distribution but have different energy
  sources. In the case of Earth, the well-established energy source is
  the solar wind. In the case of the Jovian magnetosphere, it is believed
  that internal energy is supplied by the fast planetary rotation and
  the moon Io which releases ∼1000 kg s<SUP>-1</SUP> of plasma into
  the magnetosphere. It is established that the energy accumulation and
  subsequent release lead to similar features in the magnetospheres of
  both planets. The particle data show periodic intensity fluctuations
  and plasma pressure variations. In addition, recurring signatures of
  stretching and dipolarization are observed in the magnetic field at
  the terrestrial and Jovian magnetospheres. Furthermore, the release
  process is associated with an intensification of auroral emissions. The
  typical phases for terrestrial substorms like growth, expansion and
  recovery are also found in the periodic substorms at Jupiter. As a
  lesson taken from the Jovian magnetosphere it is proposed that under
  certain conditions periodic magnetospheric substorms at Earth can be
  driven by mass-loading from the plasmasphere.

Title: The Dust Halo of Saturn’s Largest Icy Moon, Rhea
Authors: Jones, G. H.; Roussos, E.; Krupp, N.; Beckmann, U.;
   Coates, A. J.; Crary, F.; Dandouras, I.; Dikarev, V.; Dougherty,
   M. K.; Garnier, P.; Hansen, C. J.; Hendrix, A. R.; Hospodarsky,
   G. B.; Johnson, R. E.; Kempf, S.; Khurana, K. K.; Krimigis, S. M.;
   Krüger, H.; Kurth, W. S.; Lagg, A.; McAndrews, H. J.; Mitchell,
   D. G.; Paranicas, C.; Postberg, F.; Russell, C. T.; Saur, J.; Seiß,
   M.; Spahn, F.; Srama, R.; Strobel, D. F.; Tokar, R.; Wahlund, J. -E.;
   Wilson, R. J.; Woch, J.; Young, D.
Bibcode: 2008Sci...319.1380J
Altcode:
  Saturn’s moon Rhea had been considered massive enough to retain a
  thin, externally generated atmosphere capable of locally affecting
  Saturn’s magnetosphere. The Cassini spacecraft’s in situ
  observations reveal that energetic electrons are depleted in the
  moon’s vicinity. The absence of a substantial exosphere implies
  that Rhea’s magnetospheric interaction region, rather than being
  exclusively induced by sputtered gas and its products, likely contains
  solid material that can absorb magnetospheric particles. Combined
  observations from several instruments suggest that this material is
  in the form of grains and boulders up to several decimetres in size
  and orbits Rhea as an equatorial debris disk. Within this disk may
  reside denser, discrete rings or arcs of material.

Title: Energetic electron signatures of Saturn's smaller moons:
    Evidence of an arc of material at Methone
Authors: Roussos, E.; Jones, G. H.; Krupp, N.; Paranicas, C.; Mitchell,
   D. G.; Krimigis, S. M.; Woch, J.; Lagg, A.; Khurana, K.
Bibcode: 2008Icar..193..455R
Altcode:
  We present several energetic charged particle microsignatures of
  two Lagrange moons, Telesto and Helene, measured by the MIMI/LEMMS
  instrument. These small moons absorb charged particles but their
  effects are usually obscured by Tethys and Dione, the two larger
  saturnian satellites that occupy the same orbits. The scales and
  structures of these microsignatures are consistent with standard
  models for electron absorption from asteroid-sized moons in Saturn's
  radiation belts. In the context of these observations, we also examine
  the possibility that the 3 km Satellite Methone is responsible for
  two electron microsignatures detected by Cassini close to this moon's
  orbit. We infer that a previously undetected arc of material exists
  at Methone's orbit (R/2006 S5), we speculate how such a structure
  could form and what its physical characteristics and location could
  be. The origin of this arc could be linked to a possible presence of
  a faint ring produced by micrometeoroid impacts on Methone's surface,
  to E-ring dust clump formation at that distance or to temporary dust
  clouds produced by enceladian activity that spiral inwards under the
  effect of non-gravitational forces.

Title: The Nature of Running Penumbral Waves Revealed
Authors: Bloomfield, D. Shaun; Lagg, Andreas; Solanki, Sami K.
Bibcode: 2007ApJ...671.1005B
Altcode: 2007arXiv0709.3731B
  We seek to clarify the nature of running penumbral (RP) waves:
  are they chromospheric trans-sunspot waves or a visual pattern of
  upward-propagating waves? Full Stokes spectropolarimetric time series of
  the photospheric Si I λ10827 line and the chromospheric He I λ10830
  multiplet were inverted using a Milne-Eddington atmosphere. Spatial
  pixels were paired between the outer umbral/inner penumbral photosphere
  and the penumbral chromosphere using inclinations retrieved by the
  inversion and the dual-height pairings of line-of-sight velocity time
  series were studied for signatures of wave propagation using a Fourier
  phase difference analysis. The dispersion relation for radiatively
  cooling acoustic waves, modified to incorporate an inclined propagation
  direction, fits well the observed phase differences between the pairs
  of photospheric and chromospheric pixels. We have thus demonstrated
  that RP waves are in effect low-β slow-mode waves propagating along
  the magnetic field.

Title: Rhea's interaction with Saturn's magnetosphere
Authors: Jones, G. H.; Roussos, E.; Krupp, N.; Beckmann, U.; Coates,
   A. J.; Crary, F.; Dandouras, I.; Dikarev, V.; Dougherty, M. K.;
   Garnier, P.; Hansen, C. J.; Hendrix, A. R.; Hospodarsky, G. B.;
   Johnson, R. E.; Kempf, S.; Khurana, K.; Krimigis, S. M.; Krueger, H.;
   Kurth, W. S.; Lagg, A.; McAndrews, H. J.; Mitchell, D. G.; Paranicas,
   C.; Postberg, F.; Russell, C. T.; Saur, J.; Seiss, M.; Spahn, F.;
   Srama, R.; Strobel, D. F.; Tokar, R. L.; Wahlund, J.; Wilson, R. J.;
   Woch, J.; Young, D.
Bibcode: 2007AGUFM.P12B..05J
Altcode:
  The instruments aboard the Cassini orbiter continue to provide a
  wealth of invaluable information on plasma interactions at the icy
  moons of Saturn. 1528 km-wide Rhea is the largest of Saturn's icy
  satellites. Here, we present our analysis of data from the two closest
  flybys of this moon to date, in November 2005 and August 2007. Data from
  six Cassini instruments are presented; MIMI, CAPS, MAG, RPWS, UVIS,
  and CDA, covering the plasma, neutral gas, and dust environments of
  the moon. The complementary information provided by these instruments
  allows us to draw a picture of this moon's intriguing interaction
  with Saturn's magnetospheric plasma. We compare the results at Rhea
  to those obtained at other moons, and we present our arguments for the
  causes of variations observed in the magnetospheric electron population.

Title: Energetic charged particle absorption by Saturn's icy moons:
    future studies and new applications
Authors: Roussos, E.; Krupp, N.; Jones, G. H.; Paranicas, C.; Mitchell,
   D. G.; Krimigis, S. M.; Motschmann, U.; Lagg, A.; Woch, J.
Bibcode: 2007epsc.conf..905R
Altcode:
  Energetic charged particle absorption signatures by Saturn's large
  icy moons, rings and dust are an excellent tool for the study of
  the planet's magnetospheric dynamics and dust environment. After the
  first two years of the Cassini mission, relevant observations with the
  MIMI/LEMMS energetic electron sensors extended and updated the results
  from previous studies that used data from experiments on the Pioneer
  11 and the Voyager missions. The new results include values for the
  radial diffusion coefficients and their L-dependence, the observation
  of the non-axisymmetric structure of the electron drift shells, as
  well as the detection and the physical characterization of ring arcs
  at Methone's orbit and the G-ring. Furthermore, these results reveal
  that the information coded in charged particle absorption signatures
  is even greater than we could initially imagine: the highly variable
  lifetimes of electron microsignatures suggest a possible link with
  equally variable dynamic events, such as injections. The shape
  of the electron drift shells seems consistent with the effect of
  magnetospheric compression on the dayside, meaning that information
  about the magnetopause distance might be hidden in the absorption
  signature locations. The microsignature locations during high-latitude,
  close moon flybys, can also reveal the shape of the magnetic field lines
  and be used to ''calibrate" magnetic field models. Such observations
  could be crucial for the understanding of the magnetospheric and the
  space environment of Saturn.

Title: Modified p-modes in penumbral filaments?
Authors: Bloomfield, D. S.; Solanki, S. K.; Lagg, A.; Borrero, J. M.;
   Cally, P. S.
Bibcode: 2007A&A...469.1155B
Altcode: 2007arXiv0705.0481B
  Aims:The primary objective of this study is to search for and identify
  wave modes within a sunspot penumbra. <BR />Methods: Infrared
  spectropolarimetric time series data are inverted using a model
  comprising two atmospheric components in each spatial pixel. Fourier
  phase difference analysis is performed on the line-of-sight velocities
  retrieved from both components to determine time delays between the
  velocity signals. In addition, the vertical separation between the
  signals in the two components is calculated from the Stokes velocity
  response functions. <BR />Results: The inversion yields two atmospheric
  components, one permeated by a nearly horizontal magnetic field, the
  other with a less-inclined magnetic field. Time delays between the
  oscillations in the two components in the frequency range 2.5-4.5 mHz
  are combined with speeds of atmospheric wave modes to determine wave
  travel distances. These are compared to expected path lengths obtained
  from response functions of the observed spectral lines in the different
  atmospheric components. Fast-mode (i.e., modified p-mode) waves exhibit
  the best agreement with the observations when propagating toward the
  sunspot at an angle ~50° to the vertical.

Title: Electron microdiffusion in the Saturnian radiation belts:
    Cassini MIMI/LEMMS observations of energetic electron absorption by
    the icy moons
Authors: Roussos, E.; Jones, G. H.; Krupp, N.; Paranicas, C.; Mitchell,
   D. G.; Lagg, A.; Woch, J.; Motschmann, U.; Krimigis, S. M.; Dougherty,
   M. K.
Bibcode: 2007JGRA..112.6214R
Altcode: 2007JGRA..11206214R
  Since Saturn orbit insertion (SOI), Cassini has performed numerous
  crossings of Saturn's inner moons' L shells. The Low-Energy
  Magnetospheric Measurement System (LEMMS) has detected a large number
  of microsignatures in its lowest-energy electron channels (20-100 keV)
  as well as in the MeV energy range. We have catalogued and analyzed more
  than 70 microsignatures in the LEMMS data from the first 22 Cassini
  orbits and have correlated their evolution with electron diffusive
  processes. Our results on the L-dependence of the radial diffusion
  coefficients, D<SUB>LL</SUB>, show that radial microdiffusion driven
  by magnetic field impulses is the dominant mechanism to account for
  their refilling. The dependency of D<SUB>LL</SUB> from equatorial
  pitch angles also points toward this mechanism. The large scattering of
  the D<SUB>LL</SUB> values at Tethys and Dione suggest that these field
  impulses might be related to injections. Our analysis also supports the,
  inferred from pre-Cassini studies, filtering effect by the icy moons
  on radially diffusing electrons, which starts at the orbit of Dione,
  at 6.28 Saturn radii, R<SUB>s</SUB>. This is suggested primarily by
  the very low radial diffusion speeds and by the characteristics of four
  microsignatures attributed to the moons Mimas and Epimetheus that all
  seem to have been formed in energies between 1.6 and 3.5 MeV. Despite
  the low D<SUB>LL</SUB>, diffusing electrons can escape absorption and
  be transported in the inner magnetosphere due to nonaxisymmetric drift
  shells, which can be detected even along the orbit of Enceladus. We
  estimate that a significant contribution to the filtering comes from
  the core of the E ring. Our results also show that L displacements due
  to the nonaxisymmetric drift shells are orders of magnitude higher than
  the icy moon L shell variability due to the nonzero eccentricities and
  inclinations, and total plasma losses on the moon surfaces should be
  reevaluated. We also examine the energy dependence of D<SUB>LL</SUB> and
  we present a series of possible explanations for the faster depletion
  of microsignatures at MeV energies. Using the high-energy resolution
  PHA channels we assess that this faster depletion could result partly
  from an increase of D<SUB>LL</SUB> with energy. The larger passbands
  of the high-energy electron detectors could amplify the erosion of
  the microsignature signal.

Title: Energetic ion composition during reconfiguration events in
    the Jovian magnetotail
Authors: Radioti, A.; Woch, J.; Kronberg, E. A.; Krupp, N.; Lagg,
   A.; Glassmeier, K. -H.; Dougherty, M. K.
Bibcode: 2007JGRA..112.6221R
Altcode: 2007JGRA..11206221R
  On the basis of the first 15 orbits of the Galileo spacecraft
  the composition of the energetic ion population of the Jovian
  magnetosphere is studied on a global scale. Analyzing data from the
  energetic particles detector onboard Galileo, we study the relative ion
  abundance ratios of S/O, S/He, O/He and p/He at various energy/nucleon
  values. Prominent enhancements of S/O, S/He, and O/He abundance ratios
  are observed in the predawn sector and are associated with substorm-like
  events in the Jovian magnetotail. During these reconfiguration
  events, frequent small-scale variations of the south-north component
  of the magnetic field are present. Acceleration by such magnetic
  field variations is examined as a possible mechanism for particle
  energization in that region. When the timescale of the magnetic field
  variation is comparable to the particle gyro period, the particle is
  accelerated by the induced electric field. It is shown that, during
  the Jovian substorm-like events, the heavier ions are more efficiently
  energized than the lighter leading to the observed ion abundances. Ion
  composition measurements in other parts of the magnetosphere have shown
  quasiperiodic 3-day modulations suggesting that the internally driven
  processes affect the ion composition in the whole magnetosphere.

Title: Observations of Running Waves in a Sunspot Chromosphere
Authors: Bloomfield, D. S.; Lagg, A.; Solanki, S. K.
Bibcode: 2007ASPC..368..239B
Altcode: 2007astro.ph..2056B
  Spectropolarimetric time series data of the primary spot of active
  region NOAA 9448 were obtained in the Si I 10827 Å line and the He I
  10830 Å multiplet with the Tenerife Infrared Polarimeter. Throughout
  the time series the spectrograph slit was fixed over a region covering
  umbra, a light bridge, penumbra, and quiet sun. We present speeds
  of running penumbral waves in the chromosphere, their relation to
  both photospheric and chromospheric umbral oscillations, and their
  dependence on the magnetic field topology.

Title: Tenerife Infrared Polarimeter II
Authors: Collados, M.; Lagg, A.; Díaz Garcí A, J. J.; Hernández
   Suárez, E.; López López, R.; Páez Mañá, E.; Solanki, S. K.
Bibcode: 2007ASPC..368..611C
Altcode:
  Since May 2005 the Tenerife Infrared Polarimeter II (TIP-II) has been
  operational at the Vacuum Tower Telescope on Tenerife. The core of the
  polarimeter is a 1024×1020 pixel infrared camera allowing for high
  precision measurements of the full Stokes vector with a pixel size of
  0.18 arcsec, corresponding to the diffraction limit of the telescope at
  1 μm. The polarimeter is able to reach a polarimetric accuracy of a few
  times 10<SUP>-4</SUP>, covering a wavelength range of 1 to 1.8 μm. With
  an upgrade in July 2006, the slit size has been increased to 77 arcsec
  allowing most active regions to be covered with a single scan. Here
  we present the technical details of the polarimeter and the camera. We
  also show some data illustrating the power of this new instrumentation.

Title: A possible intrinsic mechanism for the quasi-periodic dynamics
    of the Jovian magnetosphere
Authors: Kronberg, E. A.; Glassmeier, K. -H.; Woch, J.; Krupp, N.;
   Lagg, A.; Dougherty, M. K.
Bibcode: 2007JGRA..112.5203K
Altcode: 2007JGRA..11205203K
  Most regions of the Jovian magnetosphere covered by the Galileo
  spacecraft measurements undergo quasi-periodic modulations with a time
  period of several Earth days. These modulations appear in various field
  and particle properties. Most prominent are periodically recurring ion
  flow bursts associated with disturbances in the meridional component
  of the magnetic field in the Jovian magnetotail or variations of
  the energy spectral shape of the particle distribution associated
  with the stretching and dipolarization of the magnetic field. Each
  individual cycle of these modulations is believed to represent a
  global reconfiguration of the Jovian magnetosphere. We present a
  simple conceptual model for these periodic processes assuming (1)
  ion mass loading from internal plasma sources and (2) fast planetary
  rotation causing magnetotail field line stretching due to centrifugal
  forces. This leads to a magnetotail configuration favoring magnetic
  reconnection. Magnetic reconnection causes plasmoid formation and
  release as well as dipolarization of field lines connected to the
  planet. Continued mass loading leads again to a stretching of the tail
  field lines. Our model shows that the suggested intrinsic mechanism
  can explain the observed periodicities of several days in Jovian
  substorm-like processes.

Title: Full-Stokes Observations and Analysis of He I 10830 Å in a
    Flaring Region
Authors: Sasso, C.; Lagg, A.; Solanki, S. K.; Aznar Cuadrado, R.;
   Collados, M.
Bibcode: 2007ASPC..368..467S
Altcode:
  We present observations of the full Stokes vector in a flaring
  region, taken in the chromospheric He I 10830 Å multiplet. The data
  were recorded with the new Tenerife Infrared Polarimeter (TIP 2)
  at the German Vacuum Tower Telescope (VTT) during May 2005. The He
  profiles during the flare are extraordinary, showing extremely broad
  Stokes I absorption and very complex and spatially variable Stokes V
  signatures. We give first results on the line-of-sight velocities and
  the magnetic field vector values in the chromosphere for one observed
  Stokes profile by applying an inversion code to the He I lines.

Title: Dynamics of the Jovian Magnetosphere
Authors: Krupp, N.; Vasyliunas, V. M.; Woch, J.; Lagg, A.; Khurana,
   K. K.; Kivelson, M. G.; Mauk, B. H.; Roelof, E. C.; Williams, D. J.;
   Krimigis, S. M.; Kurth, W. S.; Frank, L. A.; Patterson, W. R.
Bibcode: 2007jupi.book..617K
Altcode:
  No abstract at ADS

Title: The Configuration of Jupiter's Magnetosphere
Authors: Khurana, K. K.; Kivelson, M. G.; Vasyliunas, V. M.; Krupp,
   N.; Woch, J.; Lagg, A.; Mauk, B. H.; Kurth, W. S.
Bibcode: 2007jupi.book..593K
Altcode:
  No abstract at ADS

Title: Supersonic downflows in the vicinity of a growing
    pore. Evidence of unresolved magnetic fine structure at chromospheric
    heights
Authors: Lagg, A.; Woch, J.; Solanki, S. K.; Krupp, N.
Bibcode: 2007A&A...462.1147L
Altcode:
  Aims:The velocity and magnetic fine structure of the chromosphere at
  the leg of an emerging magnetic loop is investigated at a location
  of supersonic downflows. <BR />Methods: We analyze a time series of
  spectropolarimetric data in the He i 1083 nm triplet covering a time
  interval of ≈70 min. The temporal evolution as well as the topology
  of the magnetic field in the downflow region are investigated. We
  apply an inversion technique based on a genetic algorithm using the
  Milne-Eddington approach. The technique is very reliable and robust in
  retrieving maps of the velocity and the magnetic field vector for both
  atmospheric components separately. <BR />Results: We observe redshifts
  corresponding to a downflow speed of up to 40 km s<SUP>-1</SUP> in the
  vicinity of a growing pore. These supersonic downflows always coexist
  with a second atmospheric component almost at rest (slow component)
  within the same resolution element. The redshifted component is more
  inclined to the solar normal than the slow component and has a different
  field strength. <BR />Conclusions: .We interpret this downflow as a
  consequence of the draining of the rising loops. The different magnetic
  field orientation of the redshifted and the slow component give rise to
  two possible interpretations: an uncombed structure of the chromosphere,
  similar to the differently inclined flux-tubes in the penumbra of
  a sunspot, or a cloud-like structure containing gas at different
  velocities in two separate height layers of the solar atmosphere.

Title: Recent advances in measuring chromospheric magnetic fields
    in the He I 10830 Å line
Authors: Lagg, A.
Bibcode: 2007AdSpR..39.1734L
Altcode:
  During the last decade advances in instrumentation, atomic physics and
  modeling have greatly improved the access to the chromospheric magnetic
  field vector. High sensitivity polarimeters like the Tenerife Infrared
  Polarimeter (TIP2, VTT) or the Spectro-Polarimeter for Infrared and
  Optical Regions (SPINOR, HAO) lead to reliable Zeeman measurements
  using the He I 10830 Å triplet. The simultaneously measured Si I
  10827 Å line provides additional information on the structure of
  the underlying photosphere. Theoretical modeling of the Hanle and the
  Paschen-Back effect helped to significantly improve the analysis of
  polarization measurements in the He I triplet, allowing to directly
  visualize the magnetic structure of spicules, polar prominences and
  active regions. Here, I will summarize the results of chromospheric
  magnetic field measurements using this interesting triplet obtained
  in the last couple of years and discuss the great potential it has
  to further uncover the complex structure of the chromosphere and its
  coupling to the photosphere.

Title: T he Performance Of The SOLO-VIM Instrument: Effects Of
    Instrumental Noise And Lossy Data Compression
Authors: Lagg, A.; Yelles, L.; Hirzberger, J.; Woch, J.; Solanki, S. K.
Bibcode: 2007ESASP.641E..69L
Altcode:
  Spectropolarimetric observations in photospheric lines reveal a
  wealth of information on physical parameters of the solar atmosphere
  like magnetic field strength and di rection or the line-of sight
  velocity. These observations require the measurement of the four Stokes
  parameters at a sample of N wavelength positions around the core of the
  spectral line, resulting in 4N images for one observation. The Visible
  light Imager and Magnetograph (VIM) instrument on board Solar Orbiter
  is capable of performing these measurements. However, the data rate
  required to transfer all 4N images with the required cadence is well
  beyond the telemetry limit. Here we use realistic, three-dimensional
  MHD simulations in order to simulate science data provided by VIM which
  are then used to test various compression techniques. We conclude that
  lossy data compression and instrumental noise have similar effects on
  the output data.

Title: S imulations Of Science Data Of The Solo-VIM Instrument
Authors: Yelles, L.; Hirzberger, J.; Lagg, A.; Woch, J.; Solanki,
   S. K.; Vögler, A.
Bibcode: 2007ESASP.641E..34Y
Altcode:
  The SolO-VIM instrument will be a two-dimensional full-Stokes
  spectro-polarimeter which will provide diffraction-limited
  vector-magnetograms, Dopplergrams, and continuum images of the solar
  photosphere. The instrument's performance depends on various parameters
  such as aperture diameter, filter characteristics, spectral- line
  sampling, and orbital position. Here we compute Stokes profiles in
  realistic 3D MHD simulations. These synthetic data are then degraded to
  match the output ex- pected from the VIM instrument, and subsequently
  inverted using a Milne-Eddington atmosphere. We present parameter
  studies in order to set up minimum require- ments on limitations of
  VIM's capabilities.

Title: Velocity distribution of chromospheric downflows
Authors: Aznar Cuadrado, R.; Solanki, S. K.; Lagg, A.
Bibcode: 2007msfa.conf..173A
Altcode:
  Infrared spectropolarimetric observations were obtained with the
  Tenerife Infrared Polarimeter (TIP) at the German Vacuum Tower
  Telescope (VTT) of the Spanish observatory of Izana, Tenerife. We
  present the velocity distributions of a large dataset composed of
  maps of the Stokes I, Q, U, and V profiles of active and quiet sun
  regions obtained in the chromospheric He I 1083.0 nm triplet. The
  line-of-sight velocities were determined by applying a multi-Gaussian
  fit to the intensity profiles. Single and double component fits were
  carried out for all datasets. We find that 18.7% of all observed
  pixels show strong downflows as evidenced by a second line profile
  component, generally shifted by more than 8 km s-1 relative to the rest
  wavelegth. The distribution of these strong down-flows displays two
  distinct populations. The slower one (near sonic and weakly supersonic
  flows) has line-of-sight velocities up to 17 km s-1 and is associated
  with moderate to strong magnetic signal (up to √(Q2 + U2 + V2)/Ic =
  0.08). Strongly supersonic downflows (reaching up to 60 km s-1) are
  found at places with weak to moderate magnetic signal, with √(Q2 +
  U2 + V2)/Ic values mainly between 0.01 and 0.03.

Title: Spectropolarimetry in the chromospheric He I 1083.0 nm
    multiplet
Authors: Sasso, C.; Lagg, A.; Solanki, S. K.
Bibcode: 2007waas.work...43S
Altcode:
  Spectropolarimetry in the He I 1083.0 nm multiplet has a great
  potential to obtain information on the magnetic field in the solar
  upper chromosphere. We apply an inversion technique to infrared
  spectropolarimetric observations, to retrieve the full magnetic vector
  and the line-of sight velocity. The observations, obtained with the
  Tenerife Infrared Polarimeter (TIP) II at the German Vacuum Tower
  Telescope (VTT), provide maps in the Stokes parameters I, Q, U and V.

Title: Modified p-modes in penumbral filaments
Authors: Bloomfield, D. S.; Lagg, A.; Solanki, S. K.; Borrero, J. M.
Bibcode: 2007msfa.conf..241B
Altcode:
  A time series analysis was performed on velocity signals in a sunspot
  penumbra to search for possible wave modes. The spectropolarimetric
  photospheric data obtained by the Tenerife Infrared Polarimeter were
  inverted using the SPINOR code. An atmospheric model comprising two
  magnetic components and one stray-light component gave an optimal fit
  to the data. Fourier phase difference analysis between line-of-sight
  velocities of both magnetic components provided time delays between
  the two atmospheres. These delays were combined with the speeds of
  atmospheric wave modes and compared to height separations derived from
  velocity response functions to determine the wave mode.

Title: Nonlinear Force-Free Magnetic Field Modelling For VIM On SO
Authors: Wiegelmann, T.; Solanki, S. K.; Yelles, L.; Lagg, A.
Bibcode: 2007ESASP.641E..19W
Altcode:
  The aim of this work is to investigate how photon noise and errors
  in the retrieval of solar magnetic parameters from measured Stokes
  profiles influences the extrapolartion of nonlinear force-free
  coronal magnetic fields from photospheric vector magnetograms. To
  do so we use a nonlinear force-free extrapolation code based on an
  optimization principle. The extrapolation methods has been extensively
  tested and applied to data from various telescopes. Here we apply the
  code artificial vector magnetograms obtained from 3-D radiation-MHD
  simulations. As a reference case we compute the coronal magnetic field
  from an ideal magnetogram and compare the result with more realistic
  magnetograms based on simulated Solar Orbiter/VIM-measurements. We
  investigate the effect of noise, ambiguities, spatial resolution,
  inversion mechanism, of Stokes profiles etc. We rate the quality of
  the reconstructed coronal magnetic field qualitatively by magnetic
  field line plots and quantitatively by a number of comparison metrices,
  e.g., the vector correlation with the exact solution and how accurate
  the free magnetic energy is computed. Not surprisingly, the instrument
  effects and noise influence the quality of the nonlinear force-free
  coronal magnetic field model. The extrapolations from realistic vector
  magnetograms show a reasonable agreement with the ideal reconstruction,
  however, and are in particular significantly better than extrapolations
  based on line-of-sight magnetograms only. High quality VIM data
  will thus allow reasonably accurate extrapolations that can serve
  as the basis for magnetic coupling science through a comparison with
  observations from EUS and EUI.

Title: Molecular Diagnostics of the Internal Structure of Starspots
    and Sunspots
Authors: Afram, N.; Berdyugina, S. V.; Fluri, D. M.; Solanki, S. K.;
   Lagg, A.; Petit, P.; Arnaud, J.
Bibcode: 2006ASPC..358..375A
Altcode:
  We have analyzed the usefulness of molecules as a diagnostic tool for
  studying solar and stellar magnetism with the molecular Zeeman and
  Paschen-Back effects. In the first part we concentrate on molecules
  that are observed in sunspots such as MgH and TiO. We present calculated
  molecular line profiles obtained by assuming magnetic fields of 2-3 kG
  and compare these synthetic Stokes profiles with spectro-polarimetric
  observations in sunspots. The good agreement between the theory and
  observations allows us to turn our attention in the second part to
  starspots to gain insight into their internal structure. We investigate
  the temperature range in which the selected molecules can serve as
  indicators for magnetic fields on highly active cool stars and compare
  synthetic Stokes profiles with our recent observations.

Title: Measuring the Magnetic Vector with the He I 10830 Å Line:
    A Rich New World
Authors: Solanki, S. K.; Lagg, A.; Aznar Cuadrado, R.; Orozco Suárez,
   D.; Collados, M.; Wiegelmann, T.; Woch, J.; Sasso, C.; Krupp, N.
Bibcode: 2006ASPC..358..431S
Altcode:
  The triplet of the He I transitions around 10830 Å not only shows a
  rich variety of Stokes profiles, but also allows the full magnetic
  vector in the upper chromosphere to be probed, thus revealing
  the magnetic structure of loops, current sheets, finely structured
  supersonic downflows, the chromospheric layers of sunspots (supporting
  the presence of uncombed fields in the penumbra), flares, and the
  quiet Sun. A very brief overview of some of the observations and
  results obtained so far is given.

Title: A New Spoke Formation Model
Authors: Jones, G. H.; Krupp, N.; Krueger, H.; Roussos, E.; Ip, W.;
   Mitchell, D. G.; Krimigis, S. M.; Woch, J.; Lagg, A.; Fraenz, M.;
   Dougherty, M. K.; Arridge, C. S.; McAndrews, H. J.
Bibcode: 2006AGUFM.P34A..06J
Altcode:
  A new model is proposed for the formation of spokes in Saturn's
  rings. We contend that they are formed by the electrostatic charging
  of sub-micron ring particles by magnetic field-aligned electron beams
  originating in Saturn's atmosphere. The existence of these beams has
  recently been confirmed by the MIMI instrument aboard Cassini. Although
  observed by MIMI outside the main ring system, the beams are also
  expected to occur closer to the planet. On striking the rings, the
  electrons charge the dust, causing the levitation of the fine grains
  above the main ring plane. A simulation of the proposed formation
  process provides strong supporting evidence for the validity of the
  process, explaining the spokes' formation locations, morphologies,
  and subsequent development as observed in Voyager images. The process
  can be tested using Cassini observations; we outline how the model's
  validity can be gauged.

Title: Icy Moon Absorption Signatures: Probes of Saturnian
    Magnetospheric Dynamics and Moon Activity
Authors: Roussos, E.; Krupp, N.; Jones, G. H.; Paranicas, C.; Mitchell,
   D. G.; Krimigis, S. M.; Motschmann, U.; Dougherty, M. K.; Lagg, A.;
   Woch, J.
Bibcode: 2006AGUFM.P51F..03R
Altcode:
  After the first flybys at the outer planets by the Pioneer and Voyager
  probes, it became evident that energetic charged particle absorption
  features in the radiation belts are important tracers of magnetospheric
  dynamical features and parameters. Absorption signatures are especially
  important for characterizing the Saturnian magnetosphere. Due to
  the spin and magnetic axes' near-alignment, losses of particles to
  the icy moon surfaces and rings are higher compared to the losses at
  other planetary magnetospheres. The refilling rate of these absorption
  features (termed "micorsignatures") can be associated with particle
  diffusion. In addition, as these microsignatures drift with the
  properties of the pre-depletion electrons, they provide us direct
  information on the drift shell structure in the radiation belts and
  the factors that influence their shape. The multiple icy moon L-shell
  crossings by the Cassini spacecraft during the first 2 years of the
  mission provided us with almost 100 electron absorption events by
  eight different moons, at various longitudinal separations from each
  one and at various electron energies. Their analysis seems to give a
  consistent picture of the electron diffusion source and puts aside a
  lot of inconsistencies that resulted from relevant Pioneer and Voyager
  studies. The presence of non-axisymmetric particle drift shells even
  down to the orbit of Enceladus (3.98 Rs), also revealed through this
  analysis, suggests either large ring current disturbances or the
  action of global or localized electric fields. Finally, despite these
  absorption signatures being observed far from the originating moons,
  they can give us hints on the nature of the local interaction between
  each moon and the magnetospheric plasma. It is, nevertheless, beyond
  any doubt that energetic charged particle absorption signatures are a
  very powerful tool that can be used to effectively probe a series of
  dynamical processes in the Saturnian magnetosphere.

Title: Supersonic Downflows in the Vicinity of a Solar Pore
Authors: Lagg, A.; Woch, J.; Solanki, S. K.; Gandorfer, A.
Bibcode: 2006ASPC..358..437L
Altcode:
  At the footpoints of magnetic arcades spanning over a site of flux
  emergence we observe strong redshifts in the He I triplet at 1083
  nm. These redshifts are associated with downflow speeds of up to
  40 km s<SUP>-1</SUP>. Within the spatial resolution of our data (1
  arcsec-2 arcsec) obtained with the Tenerife Infrared Polarimeter at
  the VTT we find an almost unshifted atmospheric component coexisting
  with the redshifted component. We were able to retrieve the magnetic
  field configuration in both the unshifted and the redshifted component
  simultaneously and infer an uncombed, fibril-like structure of the
  upper chromosphere. The supersonic downflow speeds are interpreted as
  a consequence of a significantly reduced pressure scale height above
  the pore, where the magnetic arcades are rooted. A temporal series of
  the fast downflow region reveals that the supersonic flow is maintained
  for more than one hour. Making use of the increased spatial resolution
  of the new TIP2 instrument we are working on reducing the upper limit
  on the size of the fibril-like flux channels in the upper chromosphere.

Title: Formation of Saturn's ring spokes by lightning-induced
    electron beams
Authors: Jones, G. H.; Krupp, N.; Krüger, H.; Roussos, E.; Ip,
   W. -H.; Mitchell, D. G.; Krimigis, S. M.; Woch, J.; Lagg, A.; Fränz,
   M.; Dougherty, M. K.; Arridge, C. S.; McAndrews, H. J.
Bibcode: 2006GeoRL..3321202J
Altcode:
  Spokes are near-linear markings sometimes visible on Saturn's
  rings. They are widely accepted as being electrostatically-levitated
  sheets of ~0.6 micron-radius charged grains. Previously-suggested causes
  of the grains' charging do not agree with all spoke characteristics,
  which include their rapid generation, localized formation primarily in
  Saturn's midnight-dawn sector, the seasonality of their apparitions,
  and, crucially, their morphologies. We contend that spokes are caused
  by lightning-induced electron beams striking the rings, at locations
  magnetically-connected to thunderstorms. This view is supported by
  a semi-quantitative spoke morphology simulation. Spokes' formation
  locations are further controlled by Saturn's ionospheric density,
  which reaches a near-dawn minimum where electron beams can most easily
  propagate to the rings. The beams may generate observed X-ray emission,
  supply particles to Saturn's radiation belts, and over time will modify
  the rings' constituents. Finally, we report Cassini MIMI instrument
  observations of an electron burst which displays some characteristics
  expected of a lightning-induced event.

Title: Correction to ``Ion abundance ratios in the Jovian
    magnetosphere''
Authors: Radioti, A.; Krupp, N.; Woch, J.; Lagg, A.; Glassmeier,
   K. -H.; Waldrop, L. S.
Bibcode: 2006JGRA..11110224R
Altcode:
  No abstract at ADS

Title: A New Spoke Formation Model
Authors: Jones, Geraint H.; Krupp, N.; Krueger, H.; Roussos, E.; Ip,
   W.; Mitchell, D. G.; Krimigis, S. M.; Woch, J.; Lagg, A.; Fraenz,
   M.; Dougherty, M. K.; Arridge, C. S.; McAndrews, H. J.
Bibcode: 2006DPS....38.4214J
Altcode: 2006BAAS...38..562J
  We propose a new model for the formation of spokes in Saturn's
  rings. The model involves the electrostatic charging of sub-micron
  dust grains in the rings by magnetic field-aligned electron beams. Such
  beams have recently been observed by the MIMI instrument aboard Cassini
  at 3.1 Saturn radii, outside the main ring system. It is reasonable to
  expect the beams to also occur closer to the planet. We contend that on
  striking the rings, the electron beams’ dust-charging effects cause
  the levitation of the fine grains above the main ring plane, forming
  the spokes. Using a semi-quantitative model, we explain the spokes’
  formation locations, their initial morphologies, and the subsequent
  development of their appearance as reported in studies based on Voyager
  observations. Controlling effects on the spokes’ locations are
  also proposed. We outline tests that can be carried out using Cassini
  datasets to gauge the validity of our proposed formation process. <P
  />MIMI/LEMMS work at MPS is financed by the German Bundesministerium
  für Bildung und Forschung, and by the Max Planck Gesellschaft.

Title: Milne-Eddington inversions of the He &lt;sf&gt;I&lt;/sf&gt;
10 830 Å Stokes profiles: influence of the Paschen-Back effect
Authors: Sasso, C.; Lagg, A.; Solanki, S. K.
Bibcode: 2006A&A...456..367S
Altcode: 2011arXiv1102.0898S
  Context: .The Paschen-Back effect influences the Zeeman sublevels
  of the He I multiplet at 10 830 Å, leading to changes in strength
  and in position of the Zeeman components of these lines.<BR /> Aims:
  .We illustrate the relevance of this effect using synthetic Stokes
  profiles of the He I 10 830 Å multiplet lines and investigate its
  influence on the inversion of polarimetric data.<BR /> Methods: .We
  invert data obtained with the Tenerife Infrared Polarimeter (TIP)
  at the German Vacuum Tower Telescope (VTT). We compare the results of
  inversions based on synthetic profiles calculated with and without the
  Paschen-Back effect being included.<BR /> Results: .We find that when
  taking into account the incomplete Paschen-Back effect, on average 16%
  higher field strength values are obtained. We also show that this effect
  is not the main cause for the area asymmetry exhibited by many He I
  10 830 Stokes V-profiles. This points to the importance of velocity
  and magnetic field gradients over the formation height range of these
  lines.<BR />

Title: Multi-component analysis of a flaring region in the
    chromospheric He I 1083.0 nm triplet
Authors: Sasso, C.; Lagg, A.; Solanki, S. K.
Bibcode: 2006IAUJD...3E..31S
Altcode:
  We present infrared spectropolarimetric observations of the solar active
  region NOAA 0763 obtained with the new Tenerife Infrared Polarimeter
  (TIP 2) at the German Vacuum Tower Telescope (VTT) during May 2005,
  taken in the chromospheric He I 1083.0 nm multiplet. The region was
  in the initial phase of a C2.0 flare. We observe up to 4 atmospheric
  components within the spatial resolution of our observations. The
  components are clearly separated in wavelength, the largest separation
  corresponding to downflow velocities of up to 64 km/s. We give
  preliminary results on the magnetic vector and the line-of sight
  velocity obtained by inverting the Stokes I, Q, U and V profiles of
  the He 1083.0 nm triplet.

Title: Flux Emergence In The Solar Photosphere - Diagnostics Based
    On 3-D Rradiation-MHD Simulations
Authors: Yelles Chaouche, L.; Cheung, M.; Lagg, A.; Solanki, S.
Bibcode: 2006IAUJD...3E..75Y
Altcode:
  We investigate flux tube emergence in the solar photosphere using a
  diagnostic procedure based on analyzing Stokes signals from different
  spectral lines calculated in 3-D radiation-MHD simulations. The
  simulations include the effects of radiative transport and partial
  ionization and cover layers both above and below the solar surface. The
  simulations consider the emergence of a twisted magnetic flux tube
  through the solar surface. We consider different stages in the emergence
  process, starting from the early appearance of the flux tube at the
  solar surface, and following the emergence process until the emerged
  flux looks similar to a normal bipolar region. At every stage we compute
  line profiles by numerically solving the Unno-Rachkovsky equations at
  every horizontal grid point. Then, following observational practice,
  we apply Milne-Eddington-type inversions to the synthetic spectra in
  order to retrieve different atmospheric parameters. We include the
  influence of spatial smearing on the deduced atmospheric parameters
  to identify signatures of different stages of flux emergence in the
  solar photosphere.

Title: Solar Coronal Magnetic Field Mapper
Authors: Solanki, S. K.; Raouafi, N. -E.; Gandorfer, A.; Schühle,
   U.; Lagg, A.
Bibcode: 2006ESASP.617E.160S
Altcode: 2006soho...17E.160S
  No abstract at ADS

Title: Planetary Rotation Modulation of Various Measured Plasma
Parameters in Saturns Magnetosphere: a Possible Mechanism
Authors: Mitchell, D. G.; Brandt, P. C.; Carbary, J. F.; Krimigis,
   S. M.; Mauk, B. E.; Paranicas, C. P.; Roelof, E. C.; Jones, G.;
   Krupp, N.; Lagg, A.; Gurnett, D. A.; Kurth, W. S.; Dougherty, M. K.;
   Southwood, D. J.; Saur, J.; Zarka, P.
Bibcode: 2006AGUSM.P44A..04M
Altcode:
  The period of Saturn kilometric radiation (SKR) modulation established
  by Voyagers 1 and 2 in 1980 and 1981 (10 hours, 39 minutes, 22.4 +/-
  7s) has been adopted by the International Astronomical Union as the
  official rotation period of Saturn. Other quantities seen to exhibit
  modulation at about the same period include the magnetic field,
  energetic electron spectral slope, and energetic neutral atom (ENA)
  emission. However first the Ulysses spacecraft, and later Cassini, have
  measured a significantly different the SKR period than the Voyagers
  (approximately 10 hours, 45minutes). This change is problematic,
  because if the field is truly locked to Saturns rotation, this would
  imply a huge change in angular momentum over a relatively short
  period. Furthermore, no consensus model has been accepted to explain
  how the effects of the rotation are communicated from the planetary body
  out to distances as large as over 20 Rs (Saturn radii). In this paper,
  we explore the possibility that the observed SKR period is not Saturns
  intrinsic rotation period, but rather stems from friction between
  the ionosphere and Saturns zonal wind flows. We suggest that the SKR
  location reflects a high conductivity anomaly in Saturns ionosphere,
  whereby rigid rotation is imposed on that part of the magnetosphere
  that connects via the magnetic field and field-aligned currents with
  this high conductivity anomaly (this is similar to the hypothesis of
  the camshaft model for the magnetic perturbation suggested by Espinosa
  et al., 2003). In that work, Espinosa et al. suggest that the high
  conductivity region exists because of a high order magnetic anomaly,
  that affects ionospheric conductivity locally. We extend that model
  to include a feed-back loop with the magnetosphere. In this scenario,
  a magnetospheric disturbance initially triggered by interaction with
  the field-aligned currents results in additional energy deposition in
  the ionosphere. This further increases the ionospheric conductivity,
  but more importantly ties the high conductivity region to the middle
  magnetospheric disturbance. The local zonal thermospheric winds,
  if they are in frictional equilibrium with the conducting ionosphere,
  will move the high conductivity region (and the rest of the ionosphere)
  at whatever velocity they are traveling. With the feedback between the
  magnetospheric heating and the ionospheric conductivity established, the
  field-aligned current remains rooted in the wind-convected ionosphere,
  and so the active (SKR) meridian will slowly drift away from the
  core-rooted magnetic anomaly. The process will be self-sustaining
  for a certain length of time, until it fizzles out (either because
  the magnetospheric instability is no longer sufficiently close to
  triggering, or because the source particle populations are depleted,
  or whatever). Some time later, when the magnetosphere has stored
  sufficient energy to prime the instability, it will go off again,
  again starting at the location of the magnetic anomaly. Espinosa,
  S. A., D. J. Southwood, and M. K. Dougherty, How can Saturn impose its
  rotation period in a noncorotating magnetosphere? J. Geophys. Res.,
  108(A2), 1086, doi:10.1029/2001JA005084, 2003

Title: On the fine structure of sunspot penumbrae. III. The vertical
    extension of penumbral filaments
Authors: Borrero, J. M.; Solanki, S. K.; Lagg, A.; Socas-Navarro,
   H.; Lites, B.
Bibcode: 2006A&A...450..383B
Altcode: 2005astro.ph.10586B
  In this paper we study the fine structure of the penumbra as inferred
  from the uncombed model (flux tube embedded in a magnetic surrounding)
  when applied to penumbral spectropolarimetric data from the neutral
  iron lines at 6300 Å. The inversion infers very similar radial
  dependences in the physical quantities (LOS velocity, magnetic field
  strength etc.) as those obtained from the inversion of the Fe I 1.56
  μm lines. In addition, the large Stokes V area asymmetry exhibited
  by the visible lines helps to constrain the size of the penumbral
  flux tubes. As we demonstrate here, the uncombed model is able to
  reproduce the area asymmetry with striking accuracy, returning flux
  tubes as thick as 100-300 kilometers in the vertical direction, in
  good agreement with previous investigations.

Title: Enceladus' Varying Imprint on the Magnetosphere of Saturn
Authors: Jones, G. H.; Roussos, E.; Krupp, N.; Paranicas, C.; Woch,
   J.; Lagg, A.; Mitchell, D. G.; Krimigis, S. M.; Dougherty, M. K.
Bibcode: 2006Sci...311.1412J
Altcode:
  The bombardment of Saturn's moon Enceladus by &gt;20-kiloelectron volt
  magnetospheric particles causes particle flux depletions in regions
  magnetically connected to its orbit. Irrespective of magnetospheric
  activity, proton depletions are persistent, whereas electron depletions
  are quickly erased by magnetospheric processes. Observations of these
  signatures by Cassini's Magnetospheric Imaging Instrument allow remote
  monitoring of Enceladus' gas and dust environments. This reveals
  substantial outgassing variability at the moon and suggests increased
  dust concentrations at its Lagrange points. The characteristics of
  the particle depletions additionally provide key radial diffusion
  coefficients for energetic electrons and an independent measure of
  the inner magnetosphere's rotation velocity.

Title: Anti-planetward auroral electron beams at Saturn
Authors: Saur, J.; Mauk, B. H.; Mitchell, D. G.; Krupp, N.; Khurana,
   K. K.; Livi, S.; Krimigis, S. M.; Newell, P. T.; Williams, D. J.;
   Brandt, P. C.; Lagg, A.; Roussos, E.; Dougherty, M. K.
Bibcode: 2006Natur.439..699S
Altcode:
  Strong discrete aurorae on Earth are excited by electrons, which are
  accelerated along magnetic field lines towards the planet. Surprisingly,
  electrons accelerated in the opposite direction have been recently
  observed. The mechanisms and significance of this anti-earthward
  acceleration are highly uncertain because only earthward acceleration
  was traditionally considered, and observations remain limited. It
  is also unclear whether upward acceleration of the electrons is a
  necessary part of the auroral process or simply a special feature
  of Earth's complex space environment. Here we report anti-planetward
  acceleration of electron beams in Saturn's magnetosphere along field
  lines that statistically map into regions of aurora. The energy spectrum
  of these beams is qualitatively similar to the ones observed at Earth,
  and the energy fluxes in the observed beams are comparable with the
  energies required to excite Saturn's aurora. These beams, along with
  the observations at Earth and the barely understood electron beams in
  Jupiter's magnetosphere, demonstrate that anti-planetward acceleration
  is a universal feature of aurorae. The energy contained in the beams
  shows that upward acceleration is an essential part of the overall
  auroral process.

Title: Icy moon absorption signatures reveal non-axisymmetric
drift shells in the Saturnian radiation belts: implications for a
    magnetospheric electric field?
Authors: Roussos, E.; Krupp, N.; Jones, G. H.; Paranicas, C.; Lagg,
   A.; Woch, J.; Mitchell, D. G.; Krimigis, S. M.; Dougherty, M. K.
Bibcode: 2006epsc.conf..545R
Altcode:
  Data collected during the first 22 orbits of Cassini by the MIMI/LEMMS
  experiment revealed a significant number of energetic electron
  absorption features (microsignatures) from the icy moons Enceladus,
  Tethys and Dione, between 3.8 and 7 Rs . As the absorption regions
  drift as the pre-depletion plasma, electron microsignatures can be
  used as drift-shell tracers. By organizing the observed location of the
  microsignatures with local time we find that electrons have the tendency
  to drift inward in the midnight section and outward in the noon to dusk
  sector. Displacements up to 0.5 Rs at Tethys and 0.9 Rs at Dione cannot
  only be the result of magnetopause and ring current disturbances. This
  suggests the presence of an electric field or other processes that
  cause significant deviations from drift shell axisymmetry, even down
  to 5 Rs . We investigate possible mechanisms that could account for
  these observations (such the possible influence of a dusk to dawn
  electric field). Irrespective of the mechanism responsible for the
  observed displacements, the non-axisymmetric drift shells could be in
  part responsible for plasma transport inside the L-shells of Dione and
  Tethys as the refilling of the electron microsignatures points to very
  slow radial diffusion for electrons.

Title: The Saturnian magnetosphere after two years of Cassini in
    situ results
Authors: Krupp, N.; Jones, G. H.; Roussos, E.; Lagg, A.; Mitchell,
   D. G.; Krimigis, S. M.; Arridge, C.; McAndrews, H.; Dougherty, M. K.;
   Kurth, W.
Bibcode: 2006epsc.conf..386K
Altcode:
  The Cassini spacecraft arrived at Saturn in July 2004. Since then the
  particles and fields instrument onboard have continuously monitoring the
  Saturnian magnetosphere for more than 30 orbits covering mostly the dawn
  and predawn regions. In this study we use energetic particle, magnetic
  field and plasma wave data obtained during the first two years in orbit
  to investigate the global structure of the Saturnian magnetosphere
  and its dynamics. On a global scale the Cassini data reveal a variety
  of spatial structures in the inner and outer magnetosphere as well as
  temporal variations in most of the derived properties. We will show
  local time, latitude and longitude variations of energetic particles
  and changes in the energy spectrum as well as correlations with other
  data sets. Highest intensities of energetic particles have been found
  in the radiation belts between 6 and 15 RS with a local time asymmetry
  between dawn and dusk. The outer magnetosphere beyond that distance
  sometimes show very pronounced dropouts in the magnetotail indicating
  dynamical processes in that part of the magnetosphere. Parameters
  from the plasma, magnetic field and plasma wave investigations show
  also an unexpected modulation at the planetary rotation period. The
  investigation of these modulations is key to understanding the dynamics
  of the Saturnian magnetosphere and will be discussed in the talk.

Title: Influence of the Paschen-Back effect on the results of
    polarimetric inversions of the He I 10830 Å triplet
Authors: Sasso, C.; Lagg, A.; Solanki, S. K.; Socas-Navarro, H.
Bibcode: 2006MSAIS...9..126S
Altcode:
  The He I triplet at 10830 Å has a great potential for determining the
  magnetic field vector in the upper chromosphere. The triplet is Zeeman
  sensitive (Landé factors 2.0, 1.75 and 1.25) and shows the signature of
  the Hanle effect under appropriate conditions. Additionally, the Zeeman
  sublevels are influenced by the Paschen-Back effect leading to changes
  in strength and in position of the Zeeman components of the transitions
  forming the triplet. In this work we calculate the influence of the
  Paschen-Back effect on the Stokes profiles and investigate its relevance
  to inversions on spectro-polarimetric data obtained with the Tenerife
  Infrared Polarimeter (TIP) at the German Vacuum Tower Telescope (VTT).

Title: Comparison periodic substorms at Jupiter and Earth
Authors: Kronberg, E. A.; Woch, J.; Krupp, N.; Lagg, A.; Glassmeier,
   K. -H.
Bibcode: 2006epsc.conf..483K
Altcode:
  The Energetic Particles Detector and magnetometer measurements on
  Galileo showed that the Jovian magnetosphere undergoes reconfiguration
  processes which are very similar to the characteristics of a
  terrestrial substorm. At Jupiter the reconfiguration process occurs
  quasi-periodically with a repetition period of several days. In the
  terrestrial magnetosphere periodic substorms have been occasionally
  observed. The comparison of these periodic magnetospheric disturbances
  shows that they are similar in spatial distribution as well as in
  dynamic features, in spite of that the energy sources are different. In
  the case of the Earth, the well established energy source is the solar
  wind. In the case of the Jovian magnetosphere, it is the internal
  energy supplied by mass loading of fast rotating flux tubes. The energy
  accumulation and release leads to similar features: in the particle
  data we observed periodic "sawtooth" intensity fluctuations and plasma
  pressure and bulk velocity variations. In the magnetic field reoccurring
  signatures of stretching and dipolarization are observed. Furthermore,
  the release process is associated with an intensification of auroral
  emissions. In both magnetospheres signatures of cross-tail and
  field-aligned current generations are found.

Title: The interaction of Rhea with Saturn's magnetosphere
Authors: Jones, G. H.; Roussos, E.; Krupp, N.; Lagg, A.; Woch, J.;
   Cassini MIMI Team
Bibcode: 2006epsc.conf..382J
Altcode:
  Rhea, a 1500km-wide icy satellite of Saturn, orbits the planet at
  8.7 Saturn radii. The Cassini spacecraft's single close approach
  to the moon to date occurred on November 26, 2005, approaching to
  within 500km of Rhea's surface. The LEMMS sensors of Cassini's MIMI
  instrument observed energetic (&gt;20keV) electrons and ions in the
  moon's vicinity. As expected, a significant depletion was observed
  in low energy electrons downstream of the moon in the magnetospheric
  corotation flow. This missing population constituted particles that
  struck Rhea, forming a wake downstream. In addition to this relatively
  well-understood feature, the LEMMS data revealed a wide, relatively
  shallow electron flux depletion extending for several Rhea radii both
  inbound and outbound. Energetic ions also changed their characteristics
  within this broad region - a volume of space much larger than expected
  for a magnetospheric interaction with an inert body. We present our
  interpretation of this perplexing interaction region.

Title: Comparison of the mass-release processes at Jupiter and Earth.
Authors: Kronberg, E. A.; Woch, J.; Krupp, N.; Lagg, A.; Glassmeier,
   K. -H.
Bibcode: 2006cosp...36.1712K
Altcode: 2006cosp.meet.1712K
  The study using Energetic Particles Detector and magnetometer
  measurements on Galileo discovered that the corotational flow inherent
  for the Jovian magnetosphere is disrupted by radially outward and
  inward particle bursts in the magnetotail These bursts are associated
  with transient bipolar south-north magnetic field distortions and
  were reffered to the reconfiguration events at Jupiter and they are
  very similar to terrestrial substorms in terms of the characteristic
  features The reconfiguration process in the magnetotail consists
  of a transition from a quiet loading state to a disturbed state In
  analogy with the terrestrial substorm process the initial loading
  phase resembles characteristics of the growth loading phase and the
  disturbed phase unloading resembles the expansion phase of terrestrial
  substorms The recovery phase of the Jovian reconfiguration process
  seems to be very short in relation to the other phases similar as in
  the terrestrial case A closer look at the substorm-like processes in
  the Jovian magnetosphere also reveals further features similar to the
  terrestrial substorms such as the onset of magnetic fluctuations on a
  time scale of an ion gyroperiod in the magnetotail plasma sheet boundary
  layer formation signatures of travelling compression regions and the
  formation of a post plasmoid plasma sheet The signatures of cross-tail
  and field-aligned current generations during the reconfiguration
  process e g potential drop reversed dispersion of ions and electrons
  timing of reconfiguration events support the substorm

Title: Particles and fields in Saturn's magnetosphere: Cassini
    results after 2 years in orbit
Authors: Krupp, N.; Jones, G. H.; Roussos, E.; Lagg, A.; Woch, J.;
   Mitchell, D. G.; Krimigis, S. M.; Arridge, C.; McAndrews, H.; Kurth, W.
Bibcode: 2006cosp...36.2071K
Altcode: 2006cosp.meet.2071K
  The Cassini spacecraft arrived at Saturn in July 2004 Since then the
  particles and fields instrument onboard have continuously monitoring
  the Kronian magnetosphere for more than 30 orbits In this study we use
  energetic particle and magnetic field data obtained during the first
  two years in orbit to investigate the global structure of the Saturnian
  magnetosphere and its dynamics On a global scale the Cassini data reveal
  a variety of spatial structures and temporal variations in Saturn s
  magnetosphere We will show local time latitude and longitude variations
  of energetic particles fluxes and changes in the energy spectrum as
  well as correlations with other instruments Highest intensities of
  energetic particles have been found between 6 and 15 RS with a local
  time asymmetry between dawn and dusk Parameters from the plasma magnetic
  field and plasma wave investigations show a very pronounced modulation
  at the planetary rotation period The investigation of these modulations
  is key to understanding the dynamics of the Saturnian magnetosphere

Title: Energetic particle composition during substorm-like events
    in the Jovian magnetosphere
Authors: Radioti, A.; Woch, J.; Kronberg, E.; Krupp, N.; Glassmeier,
   K. -H.; Lagg, A.
Bibcode: 2006cosp...36..660R
Altcode: 2006cosp.meet..660R
  Based on the first 15 orbits of the Galileo spacecraft the composition
  of the energetic ion population of the Jovian magnetosphere is studied
  on a global scale Analyzing data from the Energetic Particles Detector
  onboard Galileo we study the relative ion abundance ratios of S O S
  He O He and p He at various energy nucleon Prominent enhancements
  of S O S He and O He abundance ratios are observed in the predawn
  sector associated with substorm-like events in the magnetotail During
  these reconfiguration events frequent small-scale variations of the
  south-north component of the magnetic field are present Acceleration
  by such magnetic field variations is examined as a possible mechanism
  for particle energization in that region When the time scale of the
  magnetic field variation is comparable to the particle gyro period the
  particle is accelerated by the induced electric field It is shown that
  during the Jovian substorms sulfur and oxygen ions are more effectively
  energized than helium and protons generating the observed ion abundances

Title: Magnetic field measurements at different levels in the solar
    atmosphere and magnetic coupling
Authors: Solanki, S. K.; Lagg, A.
Bibcode: 2006cosp...36..916S
Altcode: 2006cosp.meet..916S
  The magnetic field couples the different layers of the solar atmosphere
  with each other To unravel this coupling we need to be able to
  measure the field at all the relevant levels Most measurements of
  the magnetic field refer to the photosphere where magnetographs
  and spectropolarimetry using the Zeeman effect have allowed the
  magnetic structure and its evolution to be studied Observations of
  the field at higher layers in the atmosphere are more rare although
  a number of techniques are available These include Zeeman-effect and
  Hanle effect based measurements in the chromosphere and the corona
  as well as radio observations of coronal magnetic field These direct
  measurements are complemented by magnetic field extrapolations starting
  from the photosphere A brief overview of results obtained by various
  techniques of magnetic field measurements is given and a more detailed
  discussion of the main results of recent measurements of the field in
  the photosphere and the upper chromosphere are presented

Title: The magnetospheric dynamics: Periodic substorms and Jupiter
    and Earth
Authors: Kronberg, E. A.; Woch, J.; Glassmeier, K. -H.; Krupp, N.;
   Lagg, A.
Bibcode: 2006cosp...36.1715K
Altcode: 2006cosp.meet.1715K
  The Jovian and terrestrial magnetospheres show both fundamental
  commonalities and differences in their dynamical behaviour The Jovian
  substorm-like process is different from the terrestrial one by the
  inherently periodic behavior The cycle of topological stretching
  dipolarization repeats every several days Storage of magnetic energy in
  the lobe region by interaction with the interplanetary medium seems not
  to be the prime driver of the reconfiguration process Rather the Jovian
  reconfiguration process is internally driven In order to confirm this
  a simple conceptual model for this periodic process was developed It
  assumes that the ion-mass loading from internal plasma sources and the
  fast planetary rotation causes magnetotail field line stretching due
  to centrifugal forces This leads to the development of a magnetotail
  configuration favoring magnetic reconnection It is established that
  the condition for the onset of a tearing mode instability is satisfied
  just before each disturbed period of the reconfiguration process This
  causes both plasmoid formation and their release with continuing mass
  loading leading to renewed stretching of tail field lines The model
  yields that the intrinsic time constant of the Jovian reconfiguration
  process depends primarily on internal parameters like the mass-loading
  rate and is affected by the external solar wind conditions This model
  shows that the suggested intrinsic mechanism can explain the observed
  periodicities of several days of the Jovian substorm-like process We
  compare the Jovian periodical mass release processes

Title: New insights into chromospheric structures from vector magnetic
    field measurements
Authors: Lagg, A.
Bibcode: 2006cosp...36..549L
Altcode: 2006cosp.meet..549L
  During the last decade advances in instrumentation atomic physics
  and modeling have greatly improved the access to the chromospheric
  magnetic field vector High sensitivity polarimeters like the Tenerife
  Infrared Polarimeter TIP2 VTT or the Spectro-Polarimeter for Infrared
  and Optical Regions SPINOR HAO lead to reliable Zeeman measurements
  using the He I 10830 nm triplet Theoretical modeling of the Hanle and
  the Paschen Back effect helped to significantly improve the analysis
  of polarization measurements in this triplet allowing to directly
  visualize the magnetic structure of spicules polar prominences and
  active regions In this presentation I will summarize the results of
  chromospheric magnetic field measurements using this interesting triplet
  obtained in the last couple of years and discuss the great potential
  it has to further uncover the complex structure of the chromosphere

Title: Temporal variability of the ion abundance ratios in the
    Jovian magnetosphere
Authors: Radioti, A.; Krupp, N.; Woch, J.; Lagg, A.; Glassmeier, K. -H.
Bibcode: 2006cosp...36..661R
Altcode: 2006cosp.meet..661R
  Galileo as the first orbiting spacecraft around Jupiter provides the
  opportunity to study globally and in an extended energy range the
  energetic particle composition of the Jovian magnetosphere Analyzing
  data from the Energetic Particles Detector onboard Galileo we study the
  relative ion abundance ratios of S O S He O He and p He at various
  energy nucleon The global coverage of the Galileo trajectories
  enables a quantitative comparison with results of previous missions
  and especially Voyager 2 for the same radial distance and local time
  The large discrepancies found are attributed to a strong energy
  dependence but also to secular variations Ion intensities exhibit
  strong time variations between the two missions Temporal variations do
  exist also on times scales of several weeks as shown by the analysis
  of consecutive Galileo orbits Large and small scale variations of the
  ion abundance ratios are related to the temporal variability of the
  Io torus and to solar wind changes Additionally time varying particle
  acceleration processes are discussed

Title: Low energy electron microsignatures at the orbit of Tethys:
    Cassini MIMI/LEMMS observations
Authors: Roussos, E.; Krupp, N.; Woch, J.; Lagg, A.; Jones, G. H.;
   Paranicas, C.; Mitchell, D. G.; Livi, S.; Krimigis, S. M.; Dougherty,
   M. K.; Armstrong, T.; Ip, W. -H.; Motschmann, U.
Bibcode: 2005GeoRL..3224107R
Altcode:
  We report on low energy electron microsignature observations by the
  Low Energy Magnetospheric Measurement System (LEMMS) in the vicinity
  of Tethys's L-shell, during the first seven orbits of the Cassini
  mission. Tethys, due to its large size, is the source of strong
  microsignatures. Shallower absorption features seen are the result
  of aged Tethys microsignatures rather than the effect of its small
  Lagrangian moons. Several remarkable observations are also discussed:
  the displacement of the microsignatures indicates that the drift shell
  deviation from axisymmetry is greater than previously expected. Midnight
  to dawn wakes have drifted toward the planet whereas noon to dusk ones
  have drifted outward, revealing possible magnetospheric convection
  effects. Double microsignatures seen for the first time, suggest
  low radial diffusion coefficients and point to dynamic events in the
  magnetosphere.

Title: Electron microsignatures from the Saturnian satellites:
    Cassini MIMI/LEMMS observations
Authors: Roussos, E.; Krupp, N.; Jones, G. H.; Lagg, A.; Woch, J.;
   Paranicas, C.; Mitchell, D. G.; Krimigis, S. M.; Dougherty, M. K.;
   Ip, W. H.; Armstrong, T. P.
Bibcode: 2005AGUFM.P43A0955R
Altcode:
  Since the Saturn Orbit Insertion in July 2004, Cassini has performed
  numerous crossings of Saturn's inner moons L-shells at various
  longitudinal distances from the moons. The Low Energy Magnetospheric
  Measurement System (LEMMS) has detected a significant number of
  absorption features, referred to as microsignatures, in the the lowest
  energy electron channels (20-200 keV). The detections occur mainly
  in the vicinity of Tethys and Dione L-shells, while microsignatures
  from Enceladus, Rhea and Mimas are less frequent. From the analysis
  of these features we present: (i) estimates of the radial diffusion
  coefficient in Saturn's radiation belts as a function of L and
  energy, including for the first time their dependence on local time,
  (ii) the region of influence that the electric fields and energetic
  events (e.g. injections) have on the electron drift shells and (iii)
  the implications for the unique interaction characteristics of each
  moon with Saturn's magnetospheric plasma. Data from the recent close
  flybys of Tethys, Dione and Rhea are also briefly discussed.

Title: Global Structure and Dynamics of the Kronian Magnetosphere:
    Cassini Results
Authors: Krupp, N.; Lagg, A.; Woch, J.; Jones, G. H.; Roussos, E.;
   Krimigis, S. M.; Livi, S.; Mitchell, D. G.; Roelof, E. C.; Paranicas,
   C.; Hamilton, D. C.; Armstrong, T. P.; Dougherty, M. K.
Bibcode: 2005AGUFM.P43A0949K
Altcode:
  Since July 2004 the Cassini spacecraft is in orbit around Saturn
  providing in-situ measurements of the Saturnian magnetosphere. Several
  magnetospheric regions could be identified including the intense
  radiation belts and ring current regions in the inner magnetosphere as
  well as the equatorial plasma sheet and the regions close to the outer
  boundaries of the magnetosphere from which the global structure as well
  as the dynamic of the Kronian magnetosphere can be studied. Using the
  energetic particle measurements from the MIMI instrument as well as the
  magnetic field measurements from the MAG instrument onboard Cassini
  we will discuss the derived pitch angle distributions, electron and
  ion energy spectra and periodicities in magnetic field components and
  particle parameters in various regions. Some of the results are (1)
  asymmetry in the particle fluxes between the day and night sector
  at comparable distances; (2) highly varying particle fluxes as a
  consequence of large-scale dynamic processes in the equatorial plasma
  sheet; (3) field-aligned bi-directional electron fluxes in the outer
  part of the Kronian magnetosphere with correlation to the Saturnian
  aurora; (4) variations of the magnetic field components and electron
  fluxes with the planetary rotation period pointing to a magnetic
  anomaly inside the planet or pointing to corotating structures in the
  Saturnian magnetotail; (5) injections and corotating structures in
  Saturn's magnetotail as a consequence of dynamical processes.

Title: Macrosignatures of the icy moons in the inner magnetosphere
    of Saturn
Authors: Jones, G. H.; Roussos, E.; Krupp, N.; Woch, J.; Lagg, A.;
   Paranicas, C.; Krimigis, S. M.; Mitchell, D. G.; Mauk, B. H.; Ip,
   W. -P.; Dougherty, M. K.
Bibcode: 2005AGUFM.P43A0958J
Altcode:
  The energetic particle population of the inner magnetosphere of
  Saturn is significantly affected by the presence of the planet's icy
  moons. Charged particles that strike the surfaces of these moons are
  removed from the magnetosphere, significantly reducing the fluxes of
  particles observed on crossing these moons' L-shells. The signatures
  have previously been separated into two classes: Microsignatures
  are temporary signatures in longitude and time observed in the
  charged-particle wakes of satellites. Macrosignatures are longitude-
  and time-averaged effects of absorbers on the radial distribution of
  particles. Here, we present an overview of the decreases in energetic
  particle fluxes observed at these moons' L-shells, as observed by the
  LEMMS portion of the MIMI instrument aboard Cassini. We concentrate
  on macrosignatures, particularly those at the L-shell of Enceladus,
  where a deep, persistent decrease in energetic protons is observed. We
  discuss these features' formation, and the possible contribution of
  E-ring material to the observed flux decreases. It has recently been
  suggested that charged particle bombardment leads to a conversion of
  water ice from a crystalline to an amorphous state. Here we discuss
  the particle evidence for persistent weathering of Enceladus's surface
  and the extent to which each charged species is likely involved in
  this process.

Title: Observation of the Spectrum and Angular Distribution of Trapped
Protons in Saturn's Inner Magnetosphere: Implications for Sources,
    Transport, and Loss
Authors: Armstrong, T.; Manweiler, J.; Krupp, N.; Lagg, A.; Krimigis,
   S.; Livi, S.; Mitchell, D.; Roelof, E.; Paranicas, C.; Hamilton, D.
Bibcode: 2005AGUFM.P43A0951A
Altcode:
  The Cassini MIMI investigation carried a set of solid state detectors
  designed in part to resolve the shape and magnitude a local minimum
  in the flux of energetic protons at about 10 MeV reported from the
  Voyager 2 flyby in 1981. Preliminary results from Cassini Saturn
  Orbit Injection (SOI) show that this reported feature of the proton
  spectrum has persisted throughout the region within Dione's orbit . We
  will report the fluxes, pitch angle distributions, and phase space
  densities along with our estimates of source and loss processes of
  Saturnian trapped protons. Further, we will attempt to reconcile our
  results with those from Voyagers 1 and 2 and Pioneer 11, especially
  regarding the inner "CRAND" source.

Title: Diagnostics of a Simulated Flux Tube Emergence
Authors: Yelles Chaouche, L.; Cheung, M.; Lagg, A.; Solanki, S.
Bibcode: 2005ESASP.600E..74Y
Altcode: 2005ESASP.600E..74C; 2005ESPM...11...74C; 2005dysu.confE..74C
  No abstract at ADS

Title: Influence of the Paschen-Back Effect on the Stokes Profiles
    of the he 10830 Å Triplet
Authors: Sasso, C.; Lagg, A.; Solanki, S. K.
Bibcode: 2005ESASP.596E..64S
Altcode: 2005ccmf.confE..64S
  No abstract at ADS

Title: Results from Chromospheric Magnetic Field Measurements
Authors: Lagg, A.
Bibcode: 2005ESASP.596E...6L
Altcode: 2005ccmf.confE...6L
  No abstract at ADS

Title: International Scientific Conference on Chromospheric and
    Coronal Magnetic Fields
Authors: Innes, D. E.; Lagg, A.; Solanki, S. A.
Bibcode: 2005ESASP.596E....I
Altcode: 2005ccmf.confE....I
  No abstract at ADS

Title: Photospheric and Chromospheric Magnetic Structure of a Sunspot
Authors: Orozco Suarez, D.; Lagg, A.; Solanki, S. K.
Bibcode: 2005ESASP.596E..59O
Altcode: 2005ccmf.confE..59O
  No abstract at ADS

Title: Magnetic Loops: a Comparison of Extrapolations from the
    Photosphere with Chromospheric Measurements
Authors: Wiegelmann, T.; Lagg, A.; Solanki, S.; Inhester, B.; Woch, J.
Bibcode: 2005ESASP.596E...7W
Altcode: 2005ccmf.confE...7W
  No abstract at ADS

Title: International Scientific Conference on Chromospheric and
    Coronal Magnetic Fields
Authors: Innes, D. E.; Lagg, A.; Solanki, S. A.
Bibcode: 2005ESASP.596.....I
Altcode: 2005ccmf.conf.....I
  No abstract at ADS

Title: Supersonic Downflows in the Solar Chromosphere are Very Common
Authors: Aznar Cuadrado, R.; Solanki, S. K.; Lagg, A.
Bibcode: 2005ESASP.596E..49A
Altcode: 2005ccmf.confE..49A
  No abstract at ADS

Title: Evidence of Enceladus and Tethys microsignatures
Authors: Paranicas, C.; Mitchell, D. G.; Livi, S.; Krimigis, S. M.;
   Roussos, E.; Krupp, N.; Woch, J.; Lagg, A.; Saur, J.; Turner, F. S.
Bibcode: 2005GeoRL..3220101P
Altcode:
  We present evidence of two icy satellite microsignatures in the Cassini
  LEMMS data. Just upstream of Enceladus, a deep and narrow decrease in
  the flux of several MeV electrons is consistent with a recent absorption
  by that moon. This microsignature is collocated with a deep depletion in
  the MeV proton flux. The proton feature is much wider than the satellite
  diameter, suggesting multiple interactions and/or losses to the E Ring
  and neutral gas. An observed increase in proton flux toward the planet
  suggests a possible inner magnetospheric source. A decrease in the
  low energy electron intensity downstream of Tethys is also consistent
  with a microsignature approximately the size of the satellite that has
  drifted slightly toward the planet near midnight. Modeling suggests
  that microsignatures near Tethys' orbit would persist for more than
  a complete rotation of Saturn and the radial diffusion coefficient is
  about 10<SUP>-9</SUP> R<SUB>S</SUB><SUP>2</SUP>/s.

Title: Dynamics of energetic particles and neutrals in Saturn's
variable magnetosphere: results from the MIMI investigation
Authors: Krimigis, S. M.; Mitchell, D. G.; Hamilton, D. C.; Krupp,
   N.; Livi, S.; Roelof, E. C.; Dandouras, J.; Mauk, B. H.; Brandt,
   P. C.; Paranicas, C. P.; Saur, J.; Armstrong, T. P.; Bolton, S.;
   Cheng, A. F.; Gloeckler, G.; Hill, M. E.; Hsieh, K. C.; Ip, W. H.;
   Lagg, A.; Lanzerotti, L. J.; McEntire, R. W.; Williams, D. J.
Bibcode: 2005DPS....37.0604K
Altcode: 2005BAAS...37Q.626K
  The Magnetospheric IMaging Instrument (MIMI) comprises three sensors:
  the Ion and Neutral Camera (INCA) provides images using energetic
  neutral atoms (ENA) and ions; the Charge-Energy-Mass-Spectrometer
  (CHEMS) determines the mass and charge state of ions; and the
  Low Energy Magnetospheric Measurement System (LEMMS) measures ion
  and electron distributions using a dual field-of-view telescope
  (Krimigis et al, Space Sci Rev,114, 2333-329, 2004). Measurements
  by MIMI after Saturn orbit insertion on 1 July 2004 have elucidated
  several new features of the planet's magnetosphere. These include: (1)
  A dynamical magnetosphere with an11-hour periodicity. (2) The first
  remotely-sensed radiation belt inside Saturn's D-ring. (3) Abundant
  water products in the magnetospheric plasma &gt; or = 10 kev/charge,
  but little nitrogen (N+/O+&lt;0.05); neutral gas is found to be a
  major mechanism for particle loss. (4) Injections of plasma in the
  ∼4-11Rs and also &gt;20Rs corotate with the planet and can last for
  several days. (5) Activity (possibly analogous to Earth's substorms)
  occurs in Saturn's magnetotail in the 20-40 Rs region during large
  magnetospheric disturbances; this has not been observed during quiet
  times. (6) Field-aligned electron beams occur in the dawn to early
  morning sector as close as ∼10 Rs, and map to latitudes of observed
  Saturn aurora. (7) A gas cloud around Titan with dimensions &gt; 1 Rs,
  with strong high ( 3200 km) altitude ENA emissions forms a continuous,
  asymmetric ``halo." (8) Titan's emission is centered on moon--hot plasma
  interaction with the exosphere; changing intensity depends on variable
  (x10-100) ion population and magnetic field orientation about Titan. (9)
  Upstream ion events have been measured to large (&lt;50 to &gt;
  800 Rs) distances; several are enriched in oxygen ions, suggesting a
  magnetospheric origin. The observations will be presented and discussed
  in the context of current models of Saturn's magnetosphere.

Title: The Saturnian plasma sheet as revealed by energetic particle
    measurements
Authors: Krupp, N.; Lagg, A.; Woch, J.; Krimigis, S. M.; Livi, S.;
   Mitchell, D. G.; Roelof, E. C.; Paranicas, C.; Mauk, B. H.; Hamilton,
   D. C.; Armstrong, T. P.; Dougherty, M. K.
Bibcode: 2005GeoRL..3220S03K
Altcode:
  Since July 2004 Cassini is in orbit around Saturn providing in-situ
  measurements of the Saturnian magnetosphere. One of the three sensors
  of the Magnetospheric Imaging Instrument (MIMI) is the Low Energy
  Magnetospheric Measurement System (LEMMS) that responds to energetic
  particles which can serve as indicators of key regions (Krimigis et al.,
  2005) and ongoing plasma processes in the magnetosphere. In this paper
  we identify and characterize, based on energetic particle and magnetic
  field measurements, the radiation belts, the plasma sheet, and the lobe
  region. The transition between plasma sheet and lobe region sometimes
  occurs very rapidly, and sometimes occurs with the period of Saturn's
  rotation. We explain the highly variable nature of the Saturnian plasma
  sheet as a combination of the geometry of the Cassini trajectory,
  together with the variable location of the boundary between open and
  closed field lines caused by a strong localized magnetic anomaly in
  the Saturnian field.

Title: Ion abundance ratios in the Jovian magnetosphere
Authors: Radioti, A.; Krupp, N.; Woch, J.; Lagg, A.; Glassmeier,
   K. -H.; Waldrop, L. S.
Bibcode: 2005JGRA..110.7225R
Altcode: 2005JGRA..11007225R
  Galileo, as the first orbiting spacecraft around Jupiter, provides
  the opportunity to study globally the composition of the energetic ion
  population in the equatorial plane of the Jovian magnetosphere. This
  enables us to derive the relative importance of the various sources and
  sinks of plasma and energetic particles in the largest magnetosphere of
  our solar system. In this paper we use data from the Energetic Particles
  Detector (EPD) on board Galileo and derive relative ion abundance
  ratio maps of S/O, S/He, O/He, and p/He. We extend the previous work
  in terms of global coverage, species, and energy range. In addition we
  compare them with previous results and especially with those derived on
  board Voyager 2. We found that the S/O abundance ratio is relatively
  constant throughout the magnetosphere decreasing slightly with radial
  distance. Within the error bars the S/O ratios could be reproduced. Only
  a minor energy dependence is observed for this ratio pointing to a
  common source for both ions. The S/He-, O/He-, and p/He-ratios decrease
  with increasing radial distance, furthering the notion that sulfur,
  oxygen, and protons originate mainly from a source within the Jovian
  system, in contrast with helium, which originates from the solar
  wind. A spectral kink observed at energies of several 100 keV/nuc
  for all species and most pronounced for helium explains the observed
  energy dependence of the ratios relative to helium. Differences in
  the abundance ratios up to more than one order of magnitude between
  sequential orbits are evidence of large temporal variations taking
  place in the Jovian magnetosphere. These variations and the strong
  energy dependence can explain the differences between the results
  derived from Galileo EPD measurements and those from Voyager data.

Title: On the fine structure of sunspot penumbrae. II. The nature
    of the Evershed flow
Authors: Borrero, J. M.; Lagg, A.; Solanki, S. K.; Collados, M.
Bibcode: 2005A&A...436..333B
Altcode: 2005astro.ph..3677B
  We investigate the fine structure of the sunspot penumbra by means of
  a model that allows for a flux tube in horizontal pressure balance
  with the magnetic background atmosphere in which it is embedded. We
  apply this model to spectropolarimetric observations of two neutral
  iron lines at 1.56 μm and invert several radial cuts in the penumbra
  of the same sunspot at two different heliocentric angles. In the inner
  part of the penumbra we find hot flux tubes that are somewhat inclined
  to the horizontal. They become gradually more horizontal and cooler
  with increasing radial distance. This is accompanied by an increase
  in the velocity of the plasma and a decrease of the gas pressure
  difference between flux tube and the background component. At large
  radial distances the flow speed exceeds the critical speed and evidence
  is found for the formation of a shock front. These results are in good
  agreement with simulations of the penumbral fine structure and provide
  strong support for the siphon flow as the physical mechanism driving
  the Evershed flow.

Title: Jovian plasma sheet morphology: particle and field observations
    by the Galileo spacecraft
Authors: Waldrop, L. S.; Fritz, T. A.; Kivelson, M. G.; Khurana, K.;
   Krupp, N.; Lagg, A.
Bibcode: 2005P&SS...53..681W
Altcode:
  We present results from an investigation of the plasma sheet
  encounter signatures observed in the Jovian magnetosphere by the
  Energetic Particles Detector (EPD) and Magnetometer (MAG) onboard the
  Galileo spacecraft. Maxima in ion flux were used to identify over 500
  spacecraft encounters with the plasma sheet between radial distances
  from Jupiter from 20 to 140 R<SUB>J</SUB> during the first 25 orbits
  (4 years of data). Typical signatures of plasma sheet encounters
  show a characteristic periodicity of either 5 or 10 hours that is
  attributed to an oscillation in the relative distance between the
  spacecraft and the plasma sheet that arises from the combination of
  planetary rotation and offset magnetic and rotational axes. However,
  the energetic particle and field data also display much variability,
  including instances of intense fluxes having little to no periodicity
  that persist for several Jovian rotation periods. Abrupt changes in
  the mean distance between the plasma sheet and the spacecraft are
  suggested to account for some of the transitions between typical flux
  periodicities associated with plasma sheet encounters. Additional
  changes in the plasma sheet thickness and/or amplitude of the plasma
  sheet displacement from the location of the spacecraft are required to
  explain the cases where the periodicity breaks down but fluxes remain
  high. These changes in plasma sheet characteristics do not display an
  obvious periodicity; however, the observations suggest that dawn/dusk
  asymmetries in both the structure of the plasma sheet and the frequency
  of anomalous plasma sheet encounters are present. Evidence of a thin,
  well-ordered plasma sheet is found out to 110 R<SUB>J</SUB> in the
  dawn and midnight local time sectors, while the dusk magnetosphere
  is characterized by a thicker, more disordered plasma sheet and has a
  potentially more pronounced response to an impulsive trigger. Temporal
  variations associated with changing solar wind conditions are suggested
  to account for the anomalous plasma sheet encounters there.

Title: How To Use Magnetic Field Information For Coronal Loop
    Identification
Authors: Wiegelmann, T.; Inhester, B.; Lagg, A.; Solanki, S. K.
Bibcode: 2005SoPh..228...67W
Altcode: 2008arXiv0801.4573W
  The structure of the solar corona is dominated by the magnetic field
  because the magnetic pressure is about four orders of magnitude
  higher than the plasma pressure. Due to the high conductivity the
  emitting coronal plasma (visible, e.g., in SOHO/EIT) outlines the
  magnetic field lines. The gradient of the emitting plasma structures
  is significantly lower parallel to the magnetic field lines than
  in the perpendicular direction. Consequently information regarding
  the coronal magnetic field can be used for the interpretation of
  coronal plasma structures. We extrapolate the coronal magnetic field
  from photospheric magnetic field measurements into the corona. The
  extrapolation method depends on assumptions regarding coronal currents,
  e.g., potential fields (current-free) or force-free fields (current
  parallel to magnetic field). As a next step we project the reconstructed
  3D magnetic field lines on an EIT-image and compare with the emitting
  plasma structures. Coronal loops are identified as closed magnetic
  field lines with a high emissivity in EIT and a small gradient of the
  emissivity along the magnetic field.

Title: Saturn's Dynamic Magnetosphere: Energetic Particles and
    Neutrals from the Magnetospheric Imaging Instrument (MIMI)
Authors: Krimigis, S. M.; Mitchell, D. G.; Hamilton, D. C.; Krupp, N.;
   Livi, S.; Roelof, E. C.; Dandouras, I.; Mauk, B. H.; Brandt, P. C.;
   Paranicas, C.; Saur, J.; Armstrong, T. P.; Bolton, S.; Cheng, A. F.;
   Gloeckler, G.; Hill, M. E.; Hsieh, K.; Ip, W.; Lagg, A.; Lanzerotti,
   L. J.; McEntire, R. W.; Williams, D. J.
Bibcode: 2005AGUSM.P14A..04K
Altcode:
  The MIMI investigation comprises three sensors: the Ion and Neutral
  Camera (INCA) provides images using energetic neutral atoms (ENA)
  and ions; the Charge-Energy-Mass-Spectrometer (CHEMS) determines
  the mass and charge state of ions; and the Low Energy Magnetospheric
  Measurement System (LEMMS) measures ion and electron distributions using
  a dual field-of-view telescope (Krimigis et al., 2004). Measurements
  by MIMI following Saturn orbit insertion on 1 July 2004 revealed:
  (1) a dynamical magnetosphere with a day-night asymmetry and an
  11-hour periodicity; (2) several water-product ions (O+, OH+, H2O+),
  but little N+; (3) inferred quantities of neutral gas sufficient to
  cause major losses in the trapped ions and electrons in the middle and
  inner magnetosphere; (4) a Titan exosphere that is a copious source of
  energetic neutral atoms (ENA); (5) a previously unknown radiation belt
  residing inward of the D-ring that is most likely the result of double
  charge-exchange between the main radiation belt and the upper layers
  of Saturn's exosphere. Finally, MIMI data show evidence of injections
  of plasma on the night-side of the planet, some substorm-like in
  the magnetotail and others in the 7-10 RS region that subsequently
  corotate with the planet for a number of days before dissipating. The
  observations will be presented and discussed in the context of current
  theoretical models of Saturn's magnetosphere. Krimigis, S. M., et al.,
  Magnetosphere Imaging Instrument (MIMI) on the Cassini Mission to
  Saturn/Titan, Space Sci. Rev., volume 114/1-4, pp 233-329, 2004.

Title: Comparing magnetic field extrapolations with measurements of
    magnetic loops
Authors: Wiegelmann, T.; Lagg, A.; Solanki, S. K.; Inhester, B.;
   Woch, J.
Bibcode: 2005A&A...433..701W
Altcode: 2008arXiv0801.4519W
  We compare magnetic field extrapolations from a photospheric magnetogram
  with the observationally inferred structure of magnetic loops in
  a newly developed active region. This is the first time that the
  reconstructed 3D-topology of the magnetic field is available to test
  the extrapolations. We compare the observations with potential fields,
  linear force-free fields and non-linear force-free fields. This
  comparison reveals that a potential field extrapolation is not
  suitable for a reconstruction of the magnetic field in this young,
  developing active region. The inclusion of field-line-parallel
  electric currents, the so called force-free approach, gives much better
  results. Furthermore, a non-linear force-free computation reproduces
  the observations better than the linear force-free approximation,
  although no free parameters are available in the former case.

Title: Overview of Results from the Cassini Magnetospheric Imaging
    Instrument (MIMI) During the First Year of Operations
Authors: Krimigis, S. M.; Mitchell, D. G.; Hamilton, D. C.; Krupp, N.;
   Livi, S.; Roelof, E. C.; Dandouras, J.; Mauk, B. H.; Brandt, J. P.;
   Paranicas, C.; Saur, J.; Armsrong, T. P.; Bolton, S.; Cheng, A. F.;
   Gloeckler, G.; Hsieh, K. C.; Ip, W. -H.; Lagg, A.; Lanzerotti, L. J.;
   McEntire, R. W.; Williams, D. J.
Bibcode: 2005LPI....36.1361K
Altcode:
  A high-level overview of MIMI results includes corotation of
  the magnetosphere, overwhelming presence of water-product ions,
  identification of a radiation belt inside the D-ring, and inferred
  presence of neutral gas absorbing ions and electrons inward of Dione's
  orbit.

Title: Mass release at Jupiter: Substorm-like processes in the
    Jovian magnetotail
Authors: Kronberg, E. A.; Woch, J.; Krupp, N.; Lagg, A.; Khurana,
   K. K.; Glassmeier, K. -H.
Bibcode: 2005JGRA..110.3211K
Altcode: 2005JGRA..11003211K
  The Jupiter orbiting spacecraft Galileo has provided evidence that
  the Jovian magnetotail is subject to a periodic process with typical
  timescales of several days by which the Jovian system is presumably
  releasing its excess iogenic mass. The mass release process resembles
  a terrestrial substorm in the sense of a global reconfiguration of the
  magnetotail. During the initial "loading" phase the plasma convection is
  at a moderate speed in the corotation direction and the Jovian plasma
  sheet appears to be in a stable configuration. In the release phase,
  reconnection through a thinned current sheet leads to radially inward
  and outward plasma flows and the ejection of plasmoids. Storage of
  magnetic energy in the lobe region seems not to be the prime driver
  of the reconfiguration process. Therefore the role of the solar
  wind as energy source is of less importance than for terrestrial
  substorms. Instead, it can be envisaged that plasma loading of fast
  rotating magnetic flux tubes and the associated centrifugal forces
  drive the reconfiguration process.

Title: Dynamics of Saturn's Magnetosphere from MIMI During Cassini's
    Orbital Insertion
Authors: Krimigis, S. M.; Mitchell, D. G.; Hamilton, D. C.; Krupp,
   N.; Livi, S.; Roelof, E. C.; Dandouras, J.; Armstrong, T. P.; Mauk,
   B. H.; Paranicas, C.; Brandt, P. C.; Bolton, S.; Cheng, A. F.; Choo,
   T.; Gloeckler, G.; Hayes, J.; Hsieh, K. C.; Ip, W. -H.; Jaskulek, S.;
   Keath, E. P.; Kirsch, E.; Kusterer, M.; Lagg, A.; Lanzerotti, L. J.;
   LaVallee, D.; Manweiler, J.; McEntire, R. W.; Rasmuss, W.; Saur, J.;
   Turner, F. S.; Williams, D. J.; Woch, J.
Bibcode: 2005Sci...307.1270K
Altcode:
  The Magnetospheric Imaging Instrument (MIMI) onboard the Cassini
  spacecraft observed the saturnian magnetosphere from January 2004
  until Saturn orbit insertion (SOI) on 1 July 2004. The MIMI sensors
  observed frequent energetic particle activity in interplanetary space
  for several months before SOI. When the imaging sensor was switched
  to its energetic neutral atom (ENA) operating mode on 20 February
  2004, at ~10<SUP>3</SUP> times Saturn's radius R<SUB>S</SUB> (0.43
  astronomical units), a weak but persistent signal was observed from the
  magnetosphere. About 10 days before SOI, the magnetosphere exhibited
  a day-night asymmetry that varied with an ~11-hour periodicity. Once
  Cassini entered the magnetosphere, in situ measurements showed
  high concentrations of H<SUP>+</SUP>, H<SUB>2</SUB><SUP>+</SUP>,
  O<SUP>+</SUP>, OH<SUP>+</SUP>, and H<SUB>2</SUB>O<SUP>+</SUP> and low
  concentrations of N<SUP>+</SUP>. The radial dependence of ion intensity
  profiles implies neutral gas densities sufficient to produce high loss
  rates of trapped ions from the middle and inner magnetosphere. ENA
  imaging has revealed a radiation belt that resides inward of the D
  ring and is probably the result of double charge exchange between the
  main radiation belt and the upper layers of Saturn's exosphere.

Title: Signature of Current Sheets as Seen by Tip at VTT in the HeI
    Multiplet at 1083.0 nm
Authors: Aznar Cuadrado, R.; Solanki, S. K.; Lagg, A.; Thomas, R. M.
Bibcode: 2004ESASP.575..593A
Altcode: 2004soho...15..593A
  No abstract at ADS

Title: Structure of Saturn's Magnetosphere as Revealed by Energetic
    Particles
Authors: Krupp, N.; Woch, J.; Lagg, A.; Lim, J.; Krimigis, S. M.;
   Mitchell, D. G.; Roelof, E. C.; Mauk, B. H.; Paranicas, C.; Livi,
   S.; Armstrong, T. P.; Dougherty, M. K.; Kurth, W. S.; Louarn, P.;
   Dandouras, I.; Hamilton, D. C.
Bibcode: 2004AGUFM.P54A..06K
Altcode:
  At the end of June/beginning of July 2004 Cassini entered the
  magnetosphere of Saturn, 24 years after the last encounter of a
  spacecraft with the planet in 1981. Cassini entered the magnetosphere
  at about 08:00 local time 15 degrees below the equatorial plane,
  crossed the ring plane at a distance of 158500 km from the planet
  and reached 80230 km during closest approach, much closer than the
  smallest distance of Voyager. We report on results from the Low Energy
  Magnetospheric Measurement System (LEMMS), one out of three detector
  systems of the Magnetospheric Imaging Instrument (MIMI). MIMI/LEMMS
  is designed to investigate the global configuration and topology
  of the Kronian magnetosphere and to study dynamical processes. Its
  double-ended sensor is able to detect energetic electrons (15 keV- 5
  MeV) and ions with energies above 30 keV separately. Several different
  regions inside the magnetosphere could be identified through changes
  and differences in the energetic particle characteristics: A lobe
  region with low ion and electron intensities, a plasma sheet region
  with higher intensities and very abrupt changes when the spacecraft
  enters/leaves the plasma sheet, the ring current region close to the
  planet with the highest measured intensities, and the region above the
  rings with extremely low particle intensities near background. Besides
  the very high intensities in the main radiation belts close to the
  planet and the very low intensities above the rings around closest
  approach results of MIMI/LEMMS observed the Kronian magnetosphere
  in a highly dynamic state indicated by so-called injection events and
  quasi-periodic fluctuations of the intensities with a period of about an
  hour. These periodicities have also been observed in magnetic field and
  plasma wave data on board Cassini. Preliminary analysis correlate these
  fluctuations with the motion of the plasma sheet of Saturn which either
  has a wavy surface or corrugated sheet structure within this period.

Title: Imaging of Saturn's magnetosphere and energetic particles
    obsered during Cassini's orbit insertion at Saturn
Authors: Krimigis, S. M.; Mitchell, D. G.; Hamilton, D. C.; Krupp,
   N.; Livi, S.; Roelof, E. C.; Dandouras, J.; Armstrong, T. P.; Mauk,
   B. H.; Paranicas, C.; Brandt, P.; Bolton, S.; Cheng, A. F.; Choo,
   T.; Gloeckler, G.; Hayes, J.; Hsieh, K. C.; Ip, W. -H.; Jaskulek, S.;
   Keath, E. P.; Kirsch, E.; Kusterer, M.; Lagg, A.; Lanzerotti, L. J.;
   LaVallee, D.; Manweiler, J.; McEntire, R. W.; Rasmuss, W.; Saur, J.;
   Turner, F. S.; Williams, D. J.
Bibcode: 2004DPS....36.0202K
Altcode: 2004BAAS...36.1067K
  The MIMI investigation comprises three sensors, the Ion and Neutral
  Camera (INCA), Charge-Energy-Mass-Spectrometer (CHEMS), and Low Energy
  Magnetospheric Measurement System (LEMMS) covering the energy ranges
  7 keV/nuc &lt; E &lt; 200 keV/nuc (ions/neutrals), 3 &lt; E &lt; 230
  keV/e (ions), and 0.02 &lt; E &lt;18 Mev (ions)/0.015 &lt; E &lt;1 Mev
  (electrons), respectively. Also, LEMMS measures high-energy electrons
  (E &gt; 3 Mev) and protons (1.6 &lt; E &lt; 160 Mev) from the back end
  of the dual field-of-view telescope. The Saturn observation sequences
  began in January, 2004 and culminated in Saturn Orbit Insertion (SOI)
  on July 1, 2004. The MIMI sensors observed substantial activity in
  interplanetary space for several months prior to SOI, including several
  interplanetary shocks associated with corotating interaction regions,
  as well as numerous increases most likely originating from particle
  streams in the vicinity of the Saturnian bow shock. When the INCA
  sensor was switched to its energetic neutral atom (ENA) operating
  mode on day 51, at ∼ 1000 RS (0.43 AU), a weak signal was observed
  denoting the presence of Saturn's magnetosphere. Results during SOI
  revealed a dynamical magnetosphere with a day-night asymmetry and an
  11-hour periodicity; several water-product ions (O+, OH+, H2O+), but
  no N+; a substantial gas cloud around Titan, but little evidence of
  a discernible torus; and sufficient (inferred) quantities of neutral
  gas that cause major losses to trapped ions in the middle and inner
  magnetosphere. Finally, INCA imaging has revealed a previously unknown
  radiation belt that resides inside the D-ring that is most likely
  the result of double charge-exchange between the main radiation belt
  and the upper layers of Saturn's exosphere. The observations will be
  presented and discussed in the context of current theoretical models.

Title: Energetic particle observations in the vicinity of Jupiter:
    Cassini MIMI/LEMMS results
Authors: Krupp, N.; Woch, J.; Lagg, A.; Livi, S.; Mitchell, D. G.;
   Krimigis, S. M.; Dougherty, M. K.; Hanlon, P. G.; Armstrong, T. P.;
   Espinosa, S. A.
Bibcode: 2004JGRA..109.9S10K
Altcode:
  We report on energetic particle measurements from the Low
  Energy Magnetospheric Measurement System (LEMMS) on board the
  Cassini spacecraft during the Jupiter flyby (October 2000 to April
  2001). Cassini passed Jupiter on its way to Saturn on the dusk flank of
  the magnetosphere and explored for the first time the dusk-to-midnight
  magnetosheath of the planet. The flyby period can be divided into
  three distinct regimes where energetic particle parameter changes
  are observed. The first period (October 2000 to 10 January 2001)
  covers the approach phase toward the planet, including bow shock
  crossings in and out of the magnetosheath as well as the closest
  approach. In this period, LEMMS responded on solar wind pressure
  pulses and recorded the passing of two interplanetary shocks. Hours
  before the first bow shock crossing, low-energy particle intensity
  increases were observed, possibly with Jovian origin. Before the
  closest approach approach to the planet two inbound and one outbound bow
  shock crossings have been observed. The second period (9-10 January)
  is the period where Cassini briefly entered the magnetosphere twice
  at about 200 R<SUB>J</SUB>. LEMMS data are only available during a
  large portion of the second encounter. Inside the magnetosphere the
  energetic electrons showed a bidirectional pitch angle distribution
  along the magnetic field, indicative of a closed magnetic field
  configuration predominantly in the north-south direction. In addition,
  quasi-periodic electron intensity variations with periods of ≈40
  min were observed. The third period (January to April 2001) covers the
  distances between 205 and 800 R<SUB>J</SUB>. The spacecraft was skimming
  along the bow shock boundary in the dusk-to-midnight sector. More than
  44 inbound and outbound bow shock crossings have been observed. The
  most interesting magnetosheath encounter occurred between day 19 and
  day 28 at distances between 300 and 400 R<SUB>J</SUB>. In that period,
  LEMMS observed strong intensification of MeV-electron fluxes to values
  similar to those measured inside the magnetosphere as reported by
  [2002]. Most of these increases in electrons were associated with
  sign changes in the north-south component of the magnetic field. We
  interpret these observations in terms of magnetic dayside reconnection
  and particle leakage through the duskside magnetosheath.

Title: Energetic ion characteristics and neutral gas interactions
    in Jupiter's magnetosphere
Authors: Mauk, B. H.; Mitchell, D. G.; McEntire, R. W.; Paranicas,
   C. P.; Roelof, E. C.; Williams, D. J.; Krimigis, S. M.; Lagg, A.
Bibcode: 2004JGRA..109.9S12M
Altcode:
  Spectra, integral moments, and composition (H, He, O, S) of
  energetic ions (50 keV to 50 MeV) are presented for selected Jupiter
  magnetospheric positions near the equator between radial distances of
  ∼6 to ∼46 Jupiter radii (R<SUB>J</SUB>), as revealed by analysis of
  the Galileo Energetic Particle Detector data. These characteristics are
  then used as the basis of interpreting and modeling reported signatures
  of energetic ion/neutral gas interactions within Jupiter's inner
  magnetosphere, particularly energetic neutral atom emissions measured
  during the Cassini spacecraft flyby of Jupiter. Key findings include
  the following: (1) sulfur ions significantly dominate the energetic
  (≥50 keV) ion density and pressure at all radial distances &gt;7
  R<SUB>J</SUB>; (2) protons dominate integral number and energy intensity
  planetward of 20-25 R<SUB>J</SUB>; (3) a distinct signature of local,
  equatorial acceleration of energetic protons is revealed between Io
  (5.9 R<SUB>J</SUB>) and Europa (9.4 R<SUB>J</SUB>); (4) significant
  spectral and compositional signatures of neutral gas interactions are
  also revealed between the orbits of Io and Europa; (5) a previously
  reported significant depletion of ring current ion populations between
  Io and Europa during the early-phase operation of Galileo (∼1995), as
  compared with observations obtained during the Voyager epoch (1979),
  has persisted and probably deepened during later Galileo phases
  (1999); and (6) detailed energetic neutral atom emission modeling,
  based on the in situ results reported here, further constrains recent
  estimates of the contents of the neutral gas torus of Europa.

Title: Thermal-magnetic relation in a sunspot and a map  of its
    Wilson depression
Authors: Mathew, S. K.; Solanki, S. K.; Lagg, A.; Collados, M.;
   Borrero, J. M.; Berdyugina, S.
Bibcode: 2004A&A...422..693M
Altcode:
  We present relations between thermal and magnetic quantities in a
  simple, isolated sunspot, as deduced from the inversion of 1.56 μm
  spectropolarimetric data. We used a combination of two infrared Fe I
  lines at 15 648.5 Å and 15 652.8 Å/ in the inversions. Due to the
  high Zeeman sensitivity of these lines, we can study this relationship
  in the entire sunspot. The relevant parameters were derived both as a
  function of location within the sunspot and of height in the atmosphere
  using an inversion technique based on response functions. In this paper
  we relate the magnetic vector with temperature. We find a non-linear
  relationship between the various components of the magnetic vector and
  temperature, which confirm the results from earlier investigations. We
  also computed the Wilson depression and the plasma β for the observed
  sunspot and compare our results with earlier findings.

Title: On the fine structure of sunspot penumbrae. I. A quantitative
    comparison of two semiempirical models with implications for the
    Evershed effect
Authors: Borrero, J. M.; Solanki, S. K.; Bellot Rubio, L. R.; Lagg,
   A.; Mathew, S. K.
Bibcode: 2004A&A...422.1093B
Altcode:
  Sunspot penumbrae exhibit prominent fine structure. Different
  interpretations of spectropolarimetric observations suggest different,
  sometimes contradictory, properties of this fine structure. In this
  paper we show that the results of inversions of penumbral infrared
  profiles based on one-component models with gradients of the atmospheric
  parameters and two-component models without gradients are compatible
  with each other. Our analysis reconciles the results of previous
  investigations and provides further support for the picture that sunspot
  penumbrae are composed of penumbral flux tubes embedded in a magnetic
  background. The magnetic field in the tubes is more horizontal and
  weaker than that of the background atmosphere. While the tubes carry
  most of the Evershed flow, the background is essentially at rest. We
  notice also that the magnetic field strength in the flux tubes drops
  much more slowly with radial distance than the background field. This
  finding is discussed as a possible driver for the Evershed flow.

Title: Energetic electrons in the inner part of the Jovian
    magnetosphere and their relation to auroral emissions
Authors: TomáS, A. T.; Woch, J.; Krupp, N.; Lagg, A.; Glassmeier,
   K. -H.; Kurth, W. S.
Bibcode: 2004JGRA..109.6203T
Altcode:
  The energetic particle distribution in the magnetosphere of
  Jupiter changes significantly between the inner and the middle
  magnetosphere. One of the most prominent changes is a transition
  of the electron pitch angle distribution (PAD) from a pancake to
  a bidirectional distribution. The transition is a persistent and
  localized feature defining a distinct spatial boundary between 10 and
  17 R<SUB>J</SUB>. We discuss the possible relation between the PAD
  boundary and some of the observed structures in the Jovian aurora. A
  comparison between the Hubble Space Telescope observations and the
  predicted ionospheric footprints of the PAD boundary indicates a good
  correlation, with a discrete belt of emissions equatorward of the main
  auroral oval. Furthermore, the precipitation energy flux associated with
  the energetic electron distribution at the PAD boundary is compatible
  with the brightness range of these auroral emissions.

Title: Charged Particle Losses near the Inner Galilean Satellites
Authors: Paranicas, C.; Lagg, A.; Krupp, N.; Woch, J.; Mauk, B. H.
Bibcode: 2004AGUSMSM51A..05P
Altcode:
  To study the losses of energetic charged particles in the inner
  magnetosphere of Jupiter, we have calculated proton phase space
  densities from the Galileo Energetic Particles Detector (EPD) data. The
  phase space density as a function of L shell is believed to obey a
  diffusion equation. In previous calculations, the phase space density
  in the inner magnetosphere has been shown to decrease inward toward
  the planet, suggesting sources at large distances, and losses due to
  satellite sweeping and other effects. The Galileo data reveal features
  indicating a loss process near the satellites Io and Europa. We also
  verify a region of strong loss just outside the orbital radius of
  Io. We will present loss rate estimates for the relevant physical
  processes within a diffusion context. These loss rate calculations,
  for instance, allow us to place an upper bound on the neutral gas
  distribution in radius (or L shell).

Title: Europa's Neutral Gas Torus
Authors: Mauk, B. H.; Mitchell, D. G.; McEntire, R. W.; Paranicas,
   C. P.; Roelof, E. C.; Williams, D. J.; Krimigis, S. M.; Lagg, A.
Bibcode: 2004AGUSMSA22A..03M
Altcode:
  In-situ energetic ion measurements from the Galileo spacecraft and
  remote energetic neutral atom (ENA) images from the Cassini spacecraft
  have been previously interpreted as revealing an unexpectedly massive
  torus of gas co-orbiting with Jupiter's moon Europa (Lagg et al.,
  2003; Mauk et al., 2003). Here we report on the results of detailed
  modeling of the ENA emission process from the Europa regions. Updates
  to the distribution and composition of the trapped energetic ion
  populations are included in the models, as are considerations of the
  partitioning of the gas products into multiple atomic and molecular
  species. Comparisons between the models and the Cassini observations
  reveal a torus with a total gas content equal to (0.5 +/- 0.2) E34 atoms
  plus molecules. This value is higher than, but within a factor of 3 of,
  an estimate inferred from a prediction of gas densities derived from
  Voyager plasma measurements and modeling of the interaction between the
  plasmas and the gases assumed to be emanating from Europa (Schreier
  et al., 1993). Lagg, A., N. Krupp, J. Woch, and D. J. Williams,
  Geophys. Res. Lett., 30, DOI 10.1029/2003GL017214, 2003. Mauk, B. H.,
  D. G. Mitchell, S. M. Krimigs, E. C. Roelof, and C. P. Paranicas,
  Nature, 241, 920, 2003. Schreier, S., A. Eviatar, V. M. Vasyliunas,
  and J. D. Richardson, J. Geophys. Res., 98, 21231, 1993.

Title: Changes of the energetic particles characteristics in the
inner part of the Jovian magnetosphere: a topological study
Authors: Tomás, A.; Woch, J.; Krupp, N.; Lagg, A.; Glassmeier,
   K. -H.; Dougherty, M. K.; Hanlon, P. G.
Bibcode: 2004P&SS...52..491T
Altcode:
  Based on 33 Galileo passages through the inner part of the Jovian
  magnetosphere, the properties of the energetic charged particle
  population are investigated. Pronounced changes in the particle
  intensities, and in their energy and pitch angle distributions (PADs)
  are generally observed. The good coverage in local time and radial
  distance provided by Galileo allowed to trace the location of the most
  distinct changes within the equatorial plane. Independent of local
  time they occur at distances between 10 and 30R<SUB>J</SUB>. Within
  this region particle intensities drop by several orders of magnitude
  and the energy spectra softens considerably. However, most prominent
  is a change of the electron PAD from a pancake or trapped (maximum at
  90°) to a distribution which maximises at different pitch angle values
  (bi-directional or butterfly distributions). The change occurs rapidly,
  usually within the time resolution of the measurements, giving rise to
  a sharp and distinct boundary. This boundary is located dependent on
  the orbit between 10 and 17R<SUB>J</SUB>. It does not exhibit striking
  local time dependencies, specifically a pronounced dawn-dusk asymmetry,
  with the exception of the boundary being slightly closer to the planet
  near noon compared to the other local times. The change in the electron
  pitch angle distribution occurs in a region where the magnetic field
  topology is still close to a dipolar field configuration. The softening
  of the particle energy spectra is collocated with the transition of the
  magnetic field from a dipolar to a current sheet topology. Possible
  connections to and implications for the Jovian high-latitude aurora
  are addressed.

Title: Retrieval of the full magnetic vector with the He I multiplet
    at 1083 nm. Maps of an emerging flux region
Authors: Lagg, A.; Woch, J.; Krupp, N.; Solanki, S. K.
Bibcode: 2004A&A...414.1109L
Altcode:
  A technique is presented to invert Stokes profiles of the He I 1083
  nm multiplet lines in order to obtain the full magnetic vector and the
  line-of-sight velocity. The technique makes use of spectropolarimetry
  connected with the Zeeman effect supplemented by a simple Hanle effect
  based diagnostic when appropriate. It takes into account effects
  like line saturation, magnetooptieffects, etc. and is coupled with a
  genetic algorithm, which ensures that the global minimum in a goodness
  of fit hypersurface is found. Tests using both artificial and real
  data demonstrated the robustness of the method. As an illustration
  maps of deduced parameters of an emerging flux region are shown and
  briefly discussed.

Title: Energetic Particles In The Vicinity Of Saturn: Cassini
    Mimi/Lemms Observations
Authors: Krupp, N.; Lagg, A.; Woch, J.; Krimigis, S. M.; Livi, S.;
   Mitchell, D. G.; Hamilton, D. C.; Armstrong, T. P.; Lanzerotti, L. J.
Bibcode: 2004cosp...35.2723K
Altcode: 2004cosp.meet.2723K
  The Cassini-Huygens mission, launched in 1997, finally reached Saturn in
  July 2004. One of the science goals of the mission is to investigate the
  magnetosphere of Saturn, the interaction of the magnetospheric plasma
  and energetic particle population with the rings, moons and the solar
  wind. The Low Energy Magnetospheric Measurement System LEMMS (one out
  of three sensors of the Magnetospheric Imaging Instrument MIMI onboard
  Cassini) is able to measure low- and high-energy electrons and ions
  separately in the energy range between 0.015 to 5 MeV for electrons
  and 0.03 to about 160 MeV for ions. The instrument is mounted on a
  programmable scan platform allowing measurements from all direction
  within the scan plane which most of the time will be perpendicular to
  the ecliptic. This configuration will allow a good coverage in pitch
  angles. We present details of the first results in the vicinity of
  Saturn in and outside of the Kronian magnetosphere during the approach
  phase and insertion phase until July 2004. We will discuss these
  results by comparing them with early Pioneer and Voyager measurements.

Title: Temporal evolution of chromospheric downflows
Authors: Lagg, Andreas; Woch, J.; Krupp, N.; Gandorfer, A.; Solanki,
   S. K.
Bibcode: 2004IAUS..223..279L
Altcode: 2005IAUS..223..279L
  At the footpoints of loops spanning a site of flux emergence, earlier
  investigated in the papers by Solanki et al. (2003) and Lagg et
  al. (2004), we find large redshifts in the He 1083 nm line coexisting
  with an almost unshifted component. The speed associated with these
  redshifts reaches values as high as 40 km/s. We interpret these
  downflows in the context of several models: the free-fall downflow of
  matter along vertical field lines (Schmidt et al. 2000), the redshift
  by downward propagating acoustic waves (Hansteen 1993) and the motion
  of condensation regions to either side of loop footpoints (Müller et
  al. 2003). We present the temporal evolution of these redshifts and
  reconstruct the magnetic field vector in these regions for both the
  redshifted and the unshifted atmospheric component.

Title: The structure and dynamics of the Jovian energetic particle
    distribution
Authors: Woch, J.; Krupp, N.; Lagg, A.; Tomás, A.
Bibcode: 2004AdSpR..33.2030W
Altcode:
  We review the recent progress made in unravelling the properties of
  the energetic particle population in the magnetosphere of Jupiter. The
  importance of the findings with respect to mechanisms driving the
  dynamics of the Jovian system is addressed. We concentrate on the
  implications of phase space density variations for particle loss and
  source mechanism. Systematic local time and radial dependencies observed
  in the characteristics of the energetic ion and electron distributions,
  specifically the particle pitch angle distributions and particle flow
  pattern are discussed. They possibly bear important information for
  disentangling those mechanisms responsible for driving the Jovian aurora
  and for identifying the magnetospheric source populations. Furthermore,
  we discuss transient particle events in the tail which point to the
  importance of reconnection for the tail dynamics.

Title: Long-term dynamics of the inner Jovian electron radiation belts
Authors: Sicard, A.; Bourdarie, S.; Krupp, N.; Lagg, A.; Boscher,
   D.; Santos-Costa, D.; Gerard, E.; Galopeau, P.; Bolton, S.; Sault,
   R.; Williams, D. J.
Bibcode: 2004AdSpR..33.2039S
Altcode:
  Long-term variations of total Jovian synchrotron emission are well
  known to vary slowly in time. Several hypotheses have been proposed
  to explain these variations, they can be solar wind driven and/or
  induced by the geometrical effect of the declination of the Earth in
  the jovicentric coordinates, D<SUB>E</SUB>. However, until now, not any
  of them have been definitely proved. We propose here to investigate,
  this long-term dynamics based on appropriate simulation from a 3D
  model, Salammbô-3D. This model has been developed to study spatial
  distribution of electrons in the inner Jovian radiation belts. We
  will carry out two different approaches, the first one being based on
  synchrotron simulation from the Salammbô code and the second one being
  based on GALILEO EPD measurements. Two-dimensional images of Jupiter
  synchrotron emission can be obtained from our model, for any geometrical
  configuration ( λ<SUB>III</SUB>(CML), D<SUB>E</SUB>). Comparisons show
  a good agreement between modeling results and VLA observations. With
  Salammbô-3D, we can also study long-term variations of total Jovian
  synchrotron emission. The role of the two geometrical factors,
  λ<SUB>III</SUB>(CML) and D<SUB>E</SUB>, will be analyzed. First, we
  will present beaming curves (evolution of Jovian synchrotron emission
  in terms of λ<SUB>III</SUB>(CML)), resulting from the simulation to
  validate the geometry of the system in the code. Then, the evolution
  of the non-thermal flux density of synchrotron emission, in terms
  of D<SUB>E</SUB>, joviographic declination of the Earth, will be
  studied. With the help of simulations resulting from Salammbô-3D,
  we will try to discriminate between geometrical induced variations
  and natural dynamics. On the other hand we will investigate on GALILEO
  EPD measurements from 1995 until now, restricted to 5-10 Rj, to find
  out any similarity with the long-term variations of non-thermal flux
  density of synchrotron emission.

Title: Microsignatures of satellite and ring absorption events
Authors: Ip, W. H.; Hsu, W. H.; Lagg, A.; Krupp, N.; Woch, J.; Livi,
   S.; Armstrong, T.; Krimigis, S. K.
Bibcode: 2004cosp...35.1517I
Altcode: 2004cosp.meet.1517I
  Energetic charged particles interact with particulate material
  in planetary magnetospheres by impact absorption and surface
  sputtering. This process is of fundamental importance in providing a
  source of neutral gas and ions of chemical composition different from
  that of the solar wind. At the same time, the absorption of the trapped
  charged particles will create dips in the corresponding intensity
  distribution. Such absorption features, sometimes of just a few tens to
  hundreds of km in dimension, could serve as a sensitive probe to the
  existence of unseen small satellites and rings. In this presentation
  we will first make a brief review of the previous observations and
  theoretical interpretations of microsignatures detected in the Saturnian
  magnetosphere by the Pioneer 11 and Voyager spacecraft. This is to be
  followed by an examination of the opportunityy provided by the Cassini
  mission in making a detailed census of small satellites and narrow
  ring arcs of transient nature by a combination of charged particle
  experiments and imaging devices.

Title: Dynamics of the Jovian magnetosphere
Authors: Krupp, N.; Vasyliunas, V. M.; Woch, J.; Lagg, A.; Khurana,
   K. K.; Kivelson, M. G.; Mauk, B. H.; Roelof, E. C.; Williams, D. J.;
   Krimigis, S. M.; Kurth, W. S.; Frank, L. A.; Paterson, W. R.
Bibcode: 2004jpsm.book..617K
Altcode:
  Radial transport; Short-term variations: plasma interchange, injection
  events, ULF waves in Jupiter's magnetosphere; Long-term variations:
  phenomena at the planetary spin period, plasmasheet dynamics;
  Boundary phenomena: variability of boundaries, boundary layers,
  boundary fluctuations, injection of particles into interplanetary space.

Title: The configuration of Jupiter's magnetosphere
Authors: Khurana, Krishan K.; Kivelson, Margaret G.; Vasyliunas,
   Vytenis M.; Krupp, Norbert; Woch, Joachim; Lagg, Andreas; Mauk,
   Barry H.; Kurth, William S.
Bibcode: 2004jpsm.book..593K
Altcode:
  The inner magnetosphere: internal magnetic field, plasma sources,
  radiation belts; The middle magnetosphere: current sheet morphology
  and structural models, thermal and energetic plasmas, magnetic field
  models of the current sheet, the structure of the middle magnetosphere,
  bend-back of the field and plasma outflow; The outer magnetosphere: the
  Chapman-Ferraro currents, magnetotail; Plasma diffusion and convection:
  how plasma moves outwards, observations; Plasma acceleration and heating
  in Jupiter's magnetosphere: ionization and charge exchange, adiabatic
  processes, reconnection and magnetotail processes, low-altitude and
  auroral processes; Local time asymmetries: influence of solar wind.

Title: Successful Measurement of the Full Magnetic Vector Near the
    Base of the Solar Corona
Authors: Solanki, S. K.; Lagg, A.; Woch, J.; Krupp, N.; Landi
   Degl'Innocenti, E.; Collados, M.
Bibcode: 2003AGUFMSH41D..05S
Altcode:
  The measurement of coronal fields has in the past generally been
  restricted to the field strength or to only some of the components of
  the magnetic vector. We present here a technique for measuring the full
  magnetic vector near the base of the solar corona. As an application
  we report on observations of a developing active region with ongoing
  magnetic flux emergence. The data allow the first measurement of the 3-D
  structure of magnetic loops. They also provide the first detection of an
  electric current sheet located near the base of the solar corona. Such
  current sheets or tangential discontinuities of the coronal magnetic
  field have long been thought to be a major source of coronal heating.

Title: Three dimensional structure of a regular sunspot from the
    inversion of IR Stokes profiles
Authors: Mathew, S. K.; Lagg, A.; Solanki, S. K.; Collados, M.;
   Borrero, J. M.; Berdyugina, S.; Krupp, N.; Woch, J.; Frutiger, C.
Bibcode: 2003A&A...410..695M
Altcode:
  The magnetic, thermal and velocity structure of a regular sunspot,
  observed close to solar disk center is presented. Spectropolarimetric
  data obtained with the Tenerife Infrared Polarimeter (TIP) in two
  infrared FeI lines at 15 648.5 Å and 15 652.8 Å are inverted
  employing a technique based on response functions to retrieve the
  atmospheric stratification at every point in the sunspot. In order
  to improve the results for the umbra, profiles of Zeeman split OH
  lines blending the FeI 15 652.8 Å are also consistently fit. Thus
  we obtain maps of temperature, line-of-sight velocity, magnetic
  field strength, inclination, and azimuth, as a function of both
  location within the sunspot and height in the atmosphere. We present
  these maps for an optical depth range between log tau<SUB>5</SUB> =
  0 and log tau<SUB>5</SUB> = -1.5, where these lines provide accurate
  results. We find decreasing magnetic field strength with increasing
  height all over the sunspot, with a particularly large vertical field
  gradient of ~ -4 G km<SUP>-1</SUP> in the umbra. We also observe the
  so called ``spine'' structures in the penumbra, i.e. extended radial
  features with a stronger and more vertical magnetic field than the
  surroundings. Also we found that the magnetic field zenith angle
  increases with height. From the velocity map it is clear that the
  Evershed flow avoids the spines and mostly concentrates in the more
  inclined intervening field. The field inclination at a few locations
  in the outer penumbra in lower layers goes beyond 90<SUP>o</SUP>. These
  locations coincide with the strongest flows in the velocity map.

Title: Three-dimensional magnetic field topology in a region of
    solar coronal heating
Authors: Solanki, S. K.; Lagg, A.; Woch, J.; Krupp, N.; Collados, M.
Bibcode: 2003Natur.425..692S
Altcode:
  Flares and X-ray jets on the Sun arise in active regions where magnetic
  flux emerges from the solar interior amd interacts with the ambient
  magnetic field. The interactions are believed to occur in electric
  current sheets separating regions of opposite magnetic polarity. The
  current sheets located in the corona or upper chromosphere have long
  been thought to act as an important source of coronal heating, requiring
  their location in the corona or upper chromosphere. The dynamics and
  energetics of these sheets are governed by a complex magnetic field
  structure that, until now, has been difficult to measure. Here we report
  the determination of the full magnetic vector in an interaction region
  near the base of the solar corona. The observations reveal two magnetic
  features that characterize young active regions on the Sun: a set of
  rising magnetic loops and a tangential discontinuity of the magnetic
  field direction, the latter being the observational signature of an
  electric current sheet. This provides strong support for coronal heating
  models based on the dissipation of magnetic energy at current sheets.

Title: Molecular Lines as Diagnostics of Solar and Stellar Magnetic
    Fields
Authors: Berdyugina, S. V.; Solanki, S. K.; Lagg, A.
Bibcode: 2003csss...12..210B
Altcode:
  Thanks to recent advances in theory we can now calculate molecular
  line profiles in the presence of magnetic fields with high accuracy,
  both in the Zeeman and Paschen-Back regimes (Berdyugina et al. 2000;
  Berdyugina &amp; Solanki 2001a). The synthetic Stokes profiles of
  various molecular species (e.g. TiO, OH, MgH, CN, FeH) have been
  compared with profiles observed in sunspots. The agreement between
  the theory and observations is remarkable. For example, the mutually
  opposite polarities of different OH lines are reproduced without
  invoking any free parameters, except the magnetic field strength and
  sunspot temperature. Introducing molecular lines into the inversion
  of sunspot spectra leads to significant improvements in the deduced
  magnetic field vector. Here we investigate how molecular lines can be
  used to deduce magnetic parameters of cool stars. We find that such
  lines are of great interest for measuring magnetic fields on cooler
  stars and in starspots.

Title: Quiet-Sun inter-network magnetic fields  observed in the
    infrared
Authors: Khomenko, E. V.; Collados, M.; Solanki, S. K.; Lagg, A.;
   Trujillo Bueno, J.
Bibcode: 2003A&A...408.1115K
Altcode:
  This paper presents the results of an investigation of the quiet Sun's
  magnetic field based on high-resolution infrared spectropolarimetric
  observations obtained with the Tenerife Infrared Polarimeter (TIP)
  at the German VTT of the Observatorio del Teide. We observed two very
  quiet regions at disc centre. The seeing was exceptionally good during
  both observing runs, being excellent during one of them. In both cases
  the network was intentionally avoided to the extent possible, to focus
  the analysis on the characteristics of the weak polarization signals
  of the inter-network regions. We find that the Stokes V profile of
  Fe I 15648 Å line in almost 50% of the pixels and Stokes Q and/or
  U in 20% of the pixels have a signal above 10<SUP>-3</SUP> (in units
  of continuum intensity I<SUB>c</SUB>), which is significantly above
  the noise level of 2-3 x 10<SUP>-4</SUP>. This implies that we detect
  fluxes as low as 2 x 10<SUP>15</SUP> Mx/px. We find evidence that we
  have detected most of the net flux that is in principle detectable at
  1<SUP>''</SUP> resolution with the Zeeman effect. The observed linear
  polarization resulting from the transverse Zeeman effect indicates that
  the magnetic fields have a broad range of inclinations, although most
  of the pixels show polarization signatures which imply an inclination
  of about 20<SUP>o</SUP>. Nearly 30% of the selected V-profiles have
  irregular shapes with 3 or more lobes, suggesting mixed polarities with
  different LOS velocity within the resolution element. The profiles are
  classified using a single value decomposition approach. The spatial
  distribution of the magnetic signal shows that profiles of different
  classes (having different velocities, splitting, asymmetries) are
  clustered together and form patches, close to the spatial resolution
  in size. Most of the field is found to be located in intergranular
  lanes. The statistical properties of the mainly inter-network field
  sampled by these observations are presented, showing that most of
  the observed fields are weak with relatively few kG features. The
  field strength distribution peaks at 350 G and has a FWHM of 300
  G. Other parameters, such as profile asymmetries, filling factors and
  line-of-sight velocities are also determined and discussed. <P />Based
  on observations with the German Vacuum Tower Telescope (VTT) operated by
  the Kiepenheuer-Institut für Sonnenphysik at the Spanish Observatorio
  del Teide of the Instituto de Astrofísica de Canarias (IAC).

Title: Infrared Polarimetry at the MPAe: The Solar Atmosphere from
    the Photosphere to the Upper Chromosphere
Authors: Lagg, Andreas; Woch, Joachim; Solanki, Sami K.; Mathew,
   Shibu; Borrero, Juan M.; Krupp, N.; Raouafi, N. E.
Bibcode: 2003ANS...324...29L
Altcode: 2003ANS...324..D04L
  No abstract at ADS

Title: In-situ observations of a neutral gas torus at Europa
Authors: Lagg, A.; Krupp, N.; Woch, J.; Williams, D. J.
Bibcode: 2003GeoRL..30.1556L
Altcode: 2003GeoRL..30k..10L
  A persistent pattern in the pitch angle distributions of energetic
  protons near the orbit of Europa has been observed with the Energetic
  Particles Detector (EPD) on board the Galileo spacecraft during each
  of the Europa orbit crossings in the last 7 years. The proton fluxes
  at energies larger than 220 keV peak at equatorial pitch angles of 90°
  whereas fluxes of lower energy protons (80-220 keV) at this pitch angle
  are depleted. We propose that a Jupiter-surrounding neutral gas torus
  in the vicinity of the orbit of Europa is responsible for the depletion
  of energetic particle fluxes by charge exchange collisions. In order
  to reproduce the observed depletion signature an average neutral number
  density of 20 to 50 cm<SUP>-3</SUP> is required.

Title: Velocity Profiles Of Energetic Particles In The Jovian
    Magnetosphere
Authors: Krupp, N.; Woch, J.; Lagg, A.
Bibcode: 2003EAEJA....10013K
Altcode:
  During the 34 orbits of the Galileo spacecraft around Jupiter in the
  years 1995--2003 the Energetic Particles Detector EPD measured angular
  distributions of energetic ions in Jupiter's equatorial plane. These
  distributions have been used to derive global velocity profiles of
  energetic ions. We present examples of these velocity profiles at
  different local times and radial distances and discuss local time
  asymmetries in Jupiter's magnetosphere.

Title: Changes of the energetic particle characteristics in the
    inner jovian magnetosphere and the relation to auroral features
Authors: Tomas, A.; Woch, J.; Krupp, N.; Lagg, A.; Glassmeier, K. -H.;
   Dougherty, M. K.; Hanlon, P. G.; Khurana, K. K.; Prange, R.
Bibcode: 2003EAEJA.....9357T
Altcode:
  Based on 33 Galileo passages through the inner part of the jovian
  magnetosphere the properties of the energetic charged particle
  population are investigated. Pronounced changes in the particle
  intensities, and in their energy and pitch angle distribution are
  generally observed. The good coverage in local time and radial
  distance provided by Galileo allowed to trace the location of the
  most distinct changes within the equatorial plane. Independent on
  local time they occur at distances between 10 R_J and 30 R_J. Within
  this region particle intensities drop by several orders of magnitude
  and the energy spectra softens considerably. However, most prominent
  is a change of the electron pitch angle distribution from a pancake
  or trapped to a bi-directional distribution with maxima close to
  0^0 and 180^0. The change occurs rapidly, usually within the time
  resolution of the measurements, giving rise to a sharp and distinct
  boundary. This boundary is located dependent on the orbit between 10
  and 17 R_J, and occurs in a region where the magnetic field topology
  is still close to a dipolar field configuration. In order to establish
  a relation to and implications for the jovian high-latitude aurora,
  the mentioned region was then mapped into the ionosphere of Jupiter,
  using the Khurana and the VIP4 model for the tracing of magnetic field
  lines. Estimation of the electron precipitation flux and a detailed
  comparison with HST observations suggest that the sharp pitch angle
  boundary is related to the transition between the belt of diffuse
  auroras and the main auroral oval of Jupiter.

Title: New Molecular Indicators of Sunspot Magnetic Fields: Infrared
    OH Lines
Authors: Berdyugina, S. V.; Solanki, S. K.; Lagg, A.
Bibcode: 2003ASPC..286..299B
Altcode: 2003ctmf.conf..299B
  No abstract at ADS

Title: Structure of a simple sunspot from the inversion of IR
    spectral data
Authors: Mathew, S. K.; Solanki, S. K.; Lagg, A.; Collados, M.;
   Berdyugina, S. V.; Frutiger, C.; Krupp, N.; Woch, J.
Bibcode: 2003AN....324..388M
Altcode:
  Analysis of spectral data of two neighboring infrared lines, Fe i
  15648.5 Å (g = 3) and Fe i 15652.9 Å (g_eff = 1.53) are carried out
  for a simple sunspot when it was near the solar disk center (mu = 0.92),
  to understand the basic structure of sunspot magnetic field. Inversions
  of Stokes profiles are carried out to derive different atmospheric
  parameters both as a function of location within the sunspot and height
  in the atmosphere. As a result of the inversion we have obtained maps
  of magnetic field strength, temperature, line-of-sight velocity, field
  inclination and azimuth for different optical depth layers between log
  (tau_ {5}) = 0 and log (tau_ {5}) = -2.0 . In this paper we present
  few results from our inversion for a layer averaged between log (tau_
  {5}) from 0.0 to -0.5.

Title: Modeling the Fine Structure of a Sunspot Penumbra through
    the Inversion of Stokes Profiles
Authors: Borrero, J. M.; Lagg, A.; Solanki, S. K.; Frutiger, C.;
   Collados, M.; Bellot Rubio, L. R.
Bibcode: 2003ASPC..286..235B
Altcode: 2003ctmf.conf..235B
  No abstract at ADS

Title: Thermal-magnetic relation of a sunspot as inferred from the
    inversion of 1.5 μm spectral data
Authors: Mathew, S. K.; Solanki, S. K.; Lagg, A.; Krupp, N.; Woch,
   J.; Collados, M.; Berdyugina, S.; Frutiger, C.
Bibcode: 2002ESASP.505..501M
Altcode: 2002IAUCo.188..501M; 2002solm.conf..501M
  We present the thermal-magnetic relation in a simple, isolated sunspot
  deduced from the inversion of 1.56 μm spectropolarimetric data. Due to
  the high Zeeman sensitivity of the g = 3, Fe I 1.5648 μm line, we can
  study this relationship in the entire sunspot. An inversion technique
  based on response functions is used to derive various parameters,
  both as a function of location within the sunspot and of height in the
  atmosphere. In this paper we attempt to relate field strength, vertical
  and radial field components and the field inclination with temperature.

Title: Statistical properties of magnetic fields in intranetwork
Authors: Khomenko, E. V.; Collados, M.; Lagg, A.; Solanki, S. K.;
   Trujillo Bueno, J.
Bibcode: 2002ESASP.505..445K
Altcode: 2002IAUCo.188..445K; 2002solm.conf..445K
  We report a study of the quiet sun's magnetic field based
  on high-resolution infrared spectropolarimetric observations
  (TIP/VTT). We find that in almost 50% of the pixels Stokes V and in 15%
  the Stokes Q and/or U profiles have a signal above 10<SUP>-3</SUP>. The
  statistical properties of the mainly intranetwork field sampled by these
  observations are presented, showing that most of the observed fields
  are weak (the field strength distribution peaks at 350 G and has a FWHM
  of 300 G) with very few kG features. The magnetized regions occupy a
  very small fill fractions (about 2%). The field changes properties on
  granular spatial scales and the size of the patches formed by similar
  profiles is close to 1". Most of the parameters of the observed
  polarization profiles show correlations with granulation parameters.

Title: Leakage of energetic particles from Jupiter's dusk
magnetosphere: Dual spacecraft observations
Authors: Krupp, N.; Woch, J.; Lagg, A.; Espinosa, S. A.; Livi, S.;
   Krimigis, S. M.; Mitchell, D. G.; Williams, D. J.; Cheng, A. F.; Mauk,
   B. H.; McEntire, R. W.; Armstrong, T. P.; Hamilton, D. C.; Gloeckler,
   G.; Dandouras, J.; Lanzerotti, L. J.
Bibcode: 2002GeoRL..29.1736K
Altcode: 2002GeoRL..29o..26K
  For the first time, two spacecraft, Galileo and Cassini, observed
  Jupiter's magnetosphere simultaneously for nearly half a year between
  October 2000 and March 2001. This provided an unprecedented opportunity
  to disentangle spatial and temporal aspects of the dynamics of the
  Jovian magnetosphere. In this paper we report new results on the source
  of the leakage of energetic particles (electrons with energy 15 keV
  to several MeV and ions with energy &gt; 30 keV) from the dusk side
  of the magnetosphere. The dual spacecraft measurements show clearly
  that magnetospheric particles leak directly into the interplanetary
  medium from the closed magnetosphere, and are the source for the
  ``upstream'' particle events [Baker et al., 1996; Zwickl et al., 1981;
  Krimigis, 1992; Haggerty and Armstrong, 1999; Anagnostopoulos et al.,
  1998] that have been reported from instruments during prior single
  spacecraft encounters with the planet. These events, consisting of
  high-energy particles of Jovian origin, have been observed throughout
  the heliosphere [Baker and Van Allen, 1976] and their propagation
  has recently been modelled [Fichtner et al., 2000; Ferreira et al.,
  2001]. Jupiter then is an important contributor to the interplanetary
  charged particle fluxes, especially within an astronomical unit of
  the planet.

Title: Particle bursts in the Jovian magnetosphere: Evidence for a
    near-Jupiter neutral line
Authors: Woch, Joachim; Krupp, Norbert; Lagg, Andreas
Bibcode: 2002GeoRL..29.1138W
Altcode: 2002GeoRL..29g..42W
  In the magnetosphere of Jupiter the plasma convection is driven
  by the planetary rotation up to considerable distances from the
  planet. However, at larger distances the rotational flow is often
  disrupted by explosive events, seen as jets of energetic particles
  propagating in the radial direction. These events are observed
  very frequently and can be regarded as an intrinsic property of the
  Jovian system. A statistical survey shows that the burst events are
  concentrated in the post-midnight tail region. Inward directed bursts
  dominate closer to the planet, outward directed bursts further away
  from the planet. The transition from mainly inward to mainly outward
  directed bursts defines the most probable location of a near-Jupiter
  neutral line. The findings corroborate early models which postulate that
  magnetic flux tubes heavily loaded with plasma originating from the moon
  Io will be stretched by the centrifugal forces up to such a degree that
  spontaneous reconnection sets in. This leads to acceleration of plasma
  and the release of plasmoids into interplanetary space. The process
  may also drive the recently observed auroral dawn storms at Jupiter.

Title: A nebula of gases from Io surrounding Jupiter
Authors: Krimigis, Stamatios M.; Mitchell, Donald G.; Hamilton, Douglas
   C.; Dandouras, Jannis; Armstrong, Thomas P.; Bolton, Scott J.; Cheng,
   Andrew F.; Gloeckler, George; Hsieh, K. C.; Keath, Edwin P.; Krupp,
   Norbert; Lagg, Andreas; Lanzerotti, Louis J.; Livi, Stefano; Mauk,
   Barry H.; McEntire, Richard W.; Roelof, Edmond C.; Wilken, Berend;
   Williams, Donald J.
Bibcode: 2002Natur.415..994K
Altcode:
  Several planetary missions have reported the presence of substantial
  numbers of energetic ions and electrons surrounding Jupiter;
  relativistic electrons are observable up to several astronomical units
  (AU) from the planet. A population of energetic (&gt;30keV) neutral
  particles also has been reported, but the instrumentation was not
  able to determine the mass or charge state of the particles, which
  were subsequently labelled energetic neutral atoms. Although images
  showing the presence of the trace element sodium were obtained,
  the source and identity of the neutral atoms-and their overall
  significance relative to the loss of charged particles from Jupiter's
  magnetosphere-were unknown. Here we report the discovery by the Cassini
  spacecraft of a fast (&gt;10<SUP>3</SUP>kms<SUP>-1</SUP>) and hot
  magnetospheric neutral wind extending more than 0.5AU from Jupiter,
  and the presence of energetic neutral atoms (both hot and cold) that
  have been accelerated by the electric field in the solar wind. We
  suggest that these atoms originate in volcanic gases from Io, undergo
  significant evolution through various electromagnetic interactions,
  escape Jupiter's magnetosphere and then populate the environment
  around the planet. Thus a `nebula' is created that extends outwards
  over hundreds of jovian radii.

Title: New Results of Energetic Particle Observations In The Duskside
    Jovian Magnetosphere
Authors: Krupp, N.; Woch, J.; Lagg, A.
Bibcode: 2002EGSGA..27.2855K
Altcode:
  We report on new results from in-situ energetic particle measurements
  in the vicin- ity of Jupiter observed during the last year 2001
  and the beginning of 2002 by the Energetic Particles Detector EPD
  onboard the Galileo spacecraft. We concentrate on so-called realtime
  data in and outside the Jovian magnetosphere from the outer dusk-
  side Jovian magnetosphere out the magnetopause location at about 100
  planetary radii (RJ). EPD, which measures electrons (15-884 keV),
  ions (30-3200 keV) and protons (80-1250 keV), Helium (27-1000 keV/n),
  Oxygen (12-562 keV/n), and Sulfur (16-310 keV/n) ions separately,
  has the capability to derive energy spectra, relative ion compo-
  sition and angular distributions. This allows us to investigate
  relative ion composition, acceleration mechanisms and particle motion
  in regions of the Jovian magnetosphere where nearly no other data are
  available. Preliminary results show that the Jovian mag- netosphere
  at a local time of 1700 LT was very active and dynamic in early 2002
  with very sharp boundary crossings around 80-100 RJ. The results will
  be discussed in the context of previous data sets at other local times
  and will be compared with MHD simulations

Title: The structure and dynamics of the Jovian energetic particle
    population
Authors: Woch, J.; Krupp, N.; Lagg, A.
Bibcode: 2002cosp...34E.936W
Altcode: 2002cosp.meetE.936W
  The comprehensive measurements performed by the Galileo spacecraft
  allowed for the first time to study in detail a planetary
  magnetosphere other than the Earth's one. The observations confirmed
  besides similarities the existence of significant differences. In
  contrast to the solar wind-controlled terrestrial magnetosphere,
  the plasma convection in the magnetosphere of Jupiter is driven by
  the fast planetary rotation up to considerable distances from the
  planet. Furthermore, strong internal plasma sources give rise to
  dynamical processes unknown from Earth. We will review the structure
  and dynamics of the Jovian system as deduced from energetic particle
  observations, focussing on the particle convection pattern, the
  formation of a near-Jupiter neutral line, substorm-like instabilities,
  and outer boundary layer processes. We will address their relevance
  for the high-latitude aurorae at Jupiter and discuss the relative
  importance of internal and solar wind energy sources.

Title: Particle Emission From The Earth and Jupiter Magnetospheres
    Measured By The Cassini-lemms-particle Detector
Authors: Kirsch, E.; Krupp, N.; Lagg, A.; Dougherty, M. K.; Krimigis,
   S. M.; Livi, S.; Armstrong, T. P.
Bibcode: 2002EGSGA..27.5423K
Altcode:
  The Cassini spacecraft passed the Earth in August 1999 and Jupiter in
  December 2000 on its way to planet Saturn. The Low Energy Magnetospheric
  Measurement System LEMMS (Ep &gt; 30 keV, Ee &gt; 15 keV) which is a
  part of the MIMI instrument ob- served particle bursts emitted from the
  Earth and Jupiter magnetospheres. We study the flux, energy and time
  behavior of such bursts and compare them for both planets. It will
  be discussed whether substorm or other effects are responsible for
  the particle acceleration and how the particles reach interplanetary
  magnetic field lines. We com- pare our results also with measurements
  obtained earlier by other Earth satellites and the Ulysses mission to
  planet Jupiter.

Title: Energetic particle measurements during the earth swing-by of
    the Cassini spacecraft in August 1999
Authors: Lagg, A.; Krupp, N.; Livi, S.; Woch, J.; Krimigis, S. M.;
   Dougherty, M. K.
Bibcode: 2001JGR...10630209L
Altcode:
  We report on energetic particle measurements from the Low-Energy
  Magnetospheric Measurement System (LEMMS) aboard the Cassini
  spacecraft during the Earth swing-by maneuver in August 1999. LEMMS
  is capable of identifying the energy and incidence direction of
  energetic ions and electrons with energies of a few tens of keV
  to several tens of MeV. Cassini flew by Earth with a velocity of
  16 kms<SUP>-1</SUP> or 9 Earth radii (R<SUB>E</SUB>) per hour,
  which means that the entire dayside magnetosphere was passed within
  1 hour. This fast flyby trajectory of the spacecraft provided a
  snapshot of the Earth's magnetosphere where key regions were passed
  within a few hours instead of typically tens of hours or days for
  orbiting spacecraft. The measurements provide a means to show the
  performance of the instrument's capabilities as well as to test models
  of energetic particle distributions within the Earth's magnetosphere
  [e.g. Sibeck et al., 1987]. Particle pitch angle distributions (PADs)
  on the inbound pass along the 1300 magnetic local time (MLT) meridian
  gradually changed from normal distributions (maximum at 90° pitch
  angle) to butterfly pitch angle distributions (maximum at intermediate
  pitch angles). Close to the plasmapause, LEMMS observed field-aligned
  bidirectional distributions. During the outbound pass through the inner
  magnetosphere at 0130 MLT, pitch angle distributions are generally
  close to isotropic. Shortly after a substorm onset, identified by
  ground-based observations and aboard the Polar spacecraft [Khan et al.,
  this issue], LEMMS observed an energy-time dispersed enhancement in
  the differential flux of low-energy electrons. We further address the
  question of whether signatures of the Earth magnetotail were observed
  at distances beyond 5000R<SUB>E</SUB> when Cassini passed through
  the Earth's downstream region. LEMMS measured a series of particle
  increases during that time. The angular distributions during these
  enhancements show that most of these particles did indeed arrive from
  the Earth's direction. Nevertheless, the lack of singly charged heavy
  ions does not allow for a definite identification of this event as a
  deep-tail encounter.

Title: Global flows of energetic ions in Jupiter's equatorial plane:
    First-order approximation
Authors: Krupp, N.; Lagg, A.; Livi, S.; Wilken, B.; Woch, J.; Roelof,
   E. C.; Williams, D. J.
Bibcode: 2001JGR...10626017K
Altcode:
  Galileo, as the first orbiting spacecraft in an outer planet's
  magnetosphere, provides the opportunity to study global energetic
  ion distributions in Jupiter's magnetosphere. We present directional
  anisotropies of energetic ion distributions measured by the Galileo
  Energetic Particles Detector (EPD). The EPD measurements of proton
  (80-1050 keV), oxygen (26-562 keV/nucleon), and sulfur (16-310
  keV/nucleon) distributions cover a wide energy range. Spatially,
  the data set includes measurements from 6 to 142 Jovian radii
  (R<SUB>J</SUB>) and covers all local times inside the Jovian
  magnetosphere. For each species a single detector head scans almost
  the entire sky (~4π sr), producing the three-dimensional angular
  distributions from which the anisotropies are derived. Consequently,
  the resulting anisotropy estimates are both global and robust. Such
  anisotropies, generally produced by convective flow, ion intensity
  gradients, and field-aligned components, have long been used to
  estimate flow velocities and to locate spatial boundaries within
  magnetospheres. They can therefore provide vital information on
  magnetospheric circulation and dynamics. We find that the EPD
  measured anisotropies in the Jovian magnetosphere are dominated by
  a component in the corotational direction punctuated by episodic
  radial components, both inward and outward. Under the assumption
  that anisotropies are produced predominantly by convective flow, we
  derive flow velocities of protons, oxygen ions, and sulfur ions. The
  validity of that approach is supported by the fact that these three
  independently derived flow velocities agree, to a large extent, in
  this approximation. Thus, for the first time, we are able to derive
  the global flow pattern in a magnetosphere of an outer planet. In
  a comparison between the first-order EPD flow velocities and those
  predicted by a magnetohydrodynamic (MHD) simulation of the Jovian
  magnetosphere, we find that qualitatively the directions appear similar,
  although no firm evidence of steady outflow of ions has been observed
  at distances covered by Galileo. A first rough comparison indicates
  that the measured first-order flow velocities are higher by at least
  a factor of 1.5 than the MHD simulation results.

Title: Observations in Jupiter's Vicinity with the Magnetospheric
    Imaging Instrument (MIMI) During Cassini/Huygens Flyby (October
    2000-March 2001)
Authors: Krimigis, S. M.; Mitchell, D. G.; Hamilton, D. G.; Livi,
   S.; Armstrong, T. P.; Cheng, A. F.; Dandouras, J.; Gloeckler, G.;
   Hsieh, K. C.; Ip, W. H.; Keath, E. P.; Kirsch, E.; Krupp, N.; Lagg,
   A.; Lanzerotti, L. J.; Mauk, B. H.; McEntire, R. W.; Roelof, E. C.;
   Wilken, B.; Williams, D. J.
Bibcode: 2001AGUSM...P51A11K
Altcode:
  The MIMI investigation comprises three sensors, the Ion and Neutral
  Camera (INCA), Charge-Energy-Mass-Spectrometer (CHEMS), and Low Energy
  Magnetospheric Measurement System (LEMMS) covering the energy ranges
  7 keV/nuc &lt;E&lt;3 Mev/nuc (ions/ &lt; 400 keV/nuc neutrals),
  3&lt;E&lt;230 keV/e (ions), and 0.02 &lt;E&lt;18 Mev (ions)/0.015
  &lt;E&lt;1 Mev (electrons), respectively. Also, LEMMS measures
  high-energy electrons (E&gt;3 Mev) and protons (1.6 &lt; E &lt; 160 Mev)
  from the back end of the dual field-of-view telescope. MIMI obtained
  data intermittently from October 2000 to March 2001 corresponding
  to distances of ~ 103RJ upstream to ~ 103RJ downstream of the
  planet. The first unambiguous image of Energetic Neutral Atoms (ENA)
  was seen at ~ 1155RJ upstream and occupied one pixel in INCA at ~
  3% statistics. The observed intensity in the range ~ 15 to 55 keV
  (hydrogen) corresponds to ~ 0.08 (cm2 s keV)-1 when scaled to 100
  RJ., i.e. similar to expectations based on Voyager 1 observations
  some 21 years earlier. Many images were obtained through, and past,
  closest approach (140 RJ; Mitchell et al, this AGU). In addition to
  ENA's, the CHEMS sensor detected several ion species of Jovian (O+,
  S+, SO2+, etc) and interstellar (He+) origin in the upstream medium
  that manifested themselves as pick-up and accelerated components,
  suggesting that cis-Jovian space is dominated by a nebula populated
  by volcanic gases from Io (Hamilton, et al, this AGU). Energetic
  electrons and ion events (LEMMS) were also present upstream and
  marked each crossing of the extended bow shock and magnetopause of the
  planet. While in the magnetosphere, field-aligned electron distributions
  provided unambiguous evidence of closed field lines to at least 200
  RJ downstream from Jupiter. Simultaneously, highly charged (S3+, S4+,
  O3+, O2+, etc) ions were seen, suggesting that plasma outflow in the
  dusk magnetotail is dominated by magnetospheric rather than solar wind
  plasma. Evidence that Jovian plasmas are present to at least ~ 850RJ
  downstream will be presented and implications discussed on overall
  outflow of magnetospheric plasma.

Title: Hot plasma heavy ion abundance in the inner Jovian
    magnetosphere (/&lt;10 R<SUB>j</SUB>)
Authors: Maclennan, C. G.; Lanzerotti, L. J.; Lagg, Andreas
Bibcode: 2001P&SS...49..275M
Altcode:
  Knowledge of the hot plasma components of the Jovian environment is
  important for several scientific problems, including the acceleration
  and transport of Jovian plasmas, the stability of the plasma sheet,
  and the bombardment, implantation, and sputtering of the surfaces of
  Jovian moons, especially Europa. The multiple flybys of the Jovian
  moon Europa during the Galileo mission have provided the opportunity to
  study the time and spatial dependence of the abundance of the dominant
  hot plasma (∼0.2-10 MeV/nucleon (n)) heavy ions in the innermost
  region of the Jovian magnetosphere (≲10 R<SUB>j</SUB>) . Reported
  here are measurements made by the CMS Δ E× E telescopes in the EPD
  instrument on the Galileo orbiter during the first six encounters with
  the moon Europa, data taken over a period of about 1.5 years. We use
  these measurements to study the hot plasma oxygen, sulfur, and sodium
  abundances near and inside the Europa orbit. The values we determine
  for these species in the energy range of 0.5-1.0 MeV/n are 0.67±0.05
  for the S/O abundance and 0.05±0.01 for the Na/O abundance, and are
  similar to previous determinations made by instruments on the Voyager
  (measurements in 1979) and Ulysses (measurements in 1992) spacecraft.

Title: Local time asymmetry of energetic ion anisotropies in the
    Jovian magnetosphere
Authors: Krupp, N.; Woch, J.; Lagg, A.; Roelof, E. C.; Williams,
   D. J.; Livi, S.; Wilken, B.
Bibcode: 2001P&SS...49..283K
Altcode:
  Since December 1995 the Galileo spacecraft is in orbit around
  Jupiter. Up to now the spacecraft performed 25 orbits through the Jovian
  system within nearly 4 years providing an excellent data coverage in
  local time specifically for distances r&lt;40 R<SUB>J</SUB>. We present
  first-order anisotropies measured in energetic ion distributions from
  the Energetic Particles Detector (EPD) onboard Galileo. In this paper,
  we concentrate on measurements in the inner Jovian magnetosphere
  at distances between 6 and 40 R<SUB>J</SUB>. Results from three
  different ion species show a pronounced local time asymmetry in the ion
  distributions at these distances especially between the dawn-prenoon
  and the dusk-premidnight sector of the magnetosphere. The predominantly
  first-order anisotropies in the co-rotation direction show larger
  amplitudes with radial outward components in the dawn sector whereas
  at dusk smaller anisotropies with small radial inward components
  are observed. Under the reasonable assumption that the anisotropies
  are primarily due to flow, we conclude that the flow pattern is
  asymmetric in local time. The flow in the dusk sector between 10 and
  40 R<SUB>J</SUB> is reduced compared to the dawn region.

Title: Energetic charged particles near Europa
Authors: Paranicas, C.; McEntire, R. W.; Cheng, A. F.; Lagg, A.;
   Williams, D. J.
Bibcode: 2000JGR...10516005P
Altcode:
  Galileo energetic particles detector (EPD) data are presented
  from several close encounters of the spacecraft with Jupiter's
  moon Europa. These data reveal significant decreases in electron
  and ion count rates very close to the moon and a few Europa
  radii downstream. The relation between count rate decreases and
  satellite absorption is analyzed because these particles sputter
  and chemically modify Europa's surface. Decreases on the plasma
  wake side of the satellite have radial extents comparable to
  satellite dimensions. Furthermore, some energetic particle wakes
  are shifted toward Jupiter from predicted locations. At some wake
  locations, electron fluxes do not get above instrument background
  levels. Corresponding electrons are lost preferentially on Europa's
  trailing hemisphere. Upstream of Europa during the E12 encounter,
  deep decreases in energetic ion count rates are observed for some
  instrument look directions. These decreases are associated with
  satellite absorption because the E12 closest approach altitude is
  smaller than relevant ion gyroradii. Other E12 decreases, such as a
  ``bite-out'' corresponding to a peak in the measured magnetic field
  intensity, are associated with ``secondary'' drifts in the radial
  direction caused by the field gradient. Pitch angle distributions
  measured during the E15 encounter (when Galileo was in Europa's wake)
  show much higher fluxes of locally mirroring particles than would be
  expected in a simple absorption signature. We suggest that a fraction
  of the upstream population escapes absorption because of the pileup
  of magnetic flux on Europa's trailing hemisphere.

Title: Plasma sheet dynamics in the Jovian magnetotail: Signatures
    For substorm-like processes ?
Authors: Woch, J.; Krupp, N.; Khurana, K. K.; Kivelson, M. G.; Roux,
   A.; Perraut, S.; Louarn, P.; Lagg, A.; Williams, D. J.; Livi, S.;
   Wilken, B.
Bibcode: 1999GeoRL..26.2137W
Altcode:
  During Galileo's orbit G2 in 1996 the Energetic Particles Detector (EPD)
  onboard the spacecraft detected a number of particle bursts with large
  radial/antisunward anisotropies in the distant Jovian magnetotail [Krupp
  et al., 1998]. In this letter we focus on a detailed analysis of one of
  the bursts. Prior to the onset of the burst, particle intensities at low
  energies increase over several hours. This phase can be interpreted as
  a plasma loading phase. It ends after the onset of strong distortions in
  the magnetic field with a bipolar excursion of the north-south component
  being the most prominent feature. The subsequent plasma sheet encounters
  show that the plasma sheet has thinned considerably. Accelerated/heated
  ion beams first from the Jovian direction and then later from the tail
  direction are seen at the plasma sheet and lobe interfaces and intense
  radio and plasma wave emissions are detected. The event is tentatively
  interpreted as a dynamical process, where the Jovian magnetotail is
  internally driven unstable by mass loading of magnetic flux tubes.

Title: Determination of the neutral number density in the Io torus
    from Galileo-EPD measurements
Authors: Lagg, A.; Krupp, N.; Woch, J.; Livi, S.; Wilken, B.; Williams,
   D. J.
Bibcode: 1998GeoRL..25.4039L
Altcode:
  During the GALILEO spacecraft encounter with Io in December 1995, the
  Energetic Particles Detector (EPD) [Williams et al., 1992] measured
  pitch angle distributions with high spatial and temporal resolution. All
  ion and electron channels show a depletion of field-aligned particles
  due to the interaction of trapped particles with the ionosphere /
  atmosphere of Jupiter. The medium nuclei channels, containing mainly
  sulphur and oxygen ions, show a second minimum for particles moving
  perpendicular to the magnetic field direction. This observation
  indicates that charge exchange between the singly-charged energetic
  ions and neutral atoms in the Io torus represents an important loss
  mechanism for energetic ions within the Io torus regions. Additionally,
  knowing the cross-sections of the involved charge exchange reactions
  it is possible to calculate the average neutral number density in
  the Io torus. The obtained result of ≈35 cm<SUP>-3</SUP> is in good
  agreement with density estimations using ground based measurements.

Title: Energetic particle bursts in the predawn Jovian magnetotail
Authors: Krupp, N.; Woch, J.; Lagg, A.; Wilken, B.; Livi, S.; Williams,
   D. J.
Bibcode: 1998GeoRL..25.1249K
Altcode:
  From September to October 1996 the Galileo spacecraft crossed through
  the distant predawn tail region of the Jovian magnetosphere. The
  Energetic Particles Detector (EPD) onboard Galileo recorded a series of
  energetic particle flow bursts in the region beyond 80 R<SUB>J</SUB>
  to the apojove at 113 R<SUB>J</SUB>. The events are similar in nature
  to an event observed with the hot plasma instrument (LECP) onboard
  Voyager 2. The individual events last for several hours and cover the
  whole energy range from 15 keV to 55 MeV. The majority of them show
  considerable intensity increases which are most prominent for heavy
  ions. The events exhibit high radially outward directed anisotropies
  suggesting strongly collimated radial outflowing ion beams. The
  Voyager event was observed beyond the corotation boundary within a
  magnetospheric boundary layer termed the magnetospheric wind region and
  consequently it was assumed that the underlying process is connected
  with a boundary layer instability. However, the Galileo observations
  show the bursts being embedded in a general corotation flow. It is
  thus suggested that the flow bursts are driven by an internal plasma
  sheet process possibly associated with a major re-configuration of
  the Jovian magnetotail. A series of five very prominent flow bursts
  observed near apojove of the orbit occurred quasi-periodically with a
  repetition period of about 2.6±0.2 days which is presumably related
  to an internal time constant of the Jovian magnetotail.

Title: Quasi-periodic modulations of the Jovian magnetotail
Authors: Woch, J.; Krupp, N.; Lagg, A.; Wilken, B.; Livi, S.; Williams,
   D. J.
Bibcode: 1998GeoRL..25.1253W
Altcode:
  Measurements with the Energetic Particles Detector (EPD) on Galileo
  orbit C9 in the Jovian magnetotail revealed the existence of distinct
  quasi-periodic variations of energetic ion intensities which are
  superimposed on the well-known 10-hour modulations due to the planetary
  rotation. The intensity variations are associated with changes of the
  particle energy spectra and the plasma flow pattern. They are clearly
  of temporal nature and not the consequence of the spacecraft passing
  through periodically separated spatial structures. The modulation period
  is about 3 days. The oscillations are most pronounced throughout the
  middle magnetotail regime (20 to 80 R<SUB>J</SUB>), however, seem to
  persist even in the deep tail region. The amplitude of the modulation is
  dependent on the particle energy. The highest energies measured (about
  1 MeV) show the strongest variations. Energetic particle features with
  similar periodicity are observed on other Galileo orbits as well. The
  cause of these modulations is unclear; however, it may be speculated
  that they correspond to a quasi-periodic transition between two basic
  states of the Jovian magnetotail which occur with a time constant
  inherent to the Jovian magnetosphere.

Title: Galileo-measured depletion of near-Io hot ring current plasmas
    since the Voyager epoch
Authors: Mauk, B. H.; McEntire, R. W.; Williams, D. J.; Lagg, A.;
   Roelof, E. C.; Krimigis, S. M.; Armstrong, T. P.; Fritz, T. A.;
   Lanzerotti, L. J.; Roederer, J. G.; Wilken, B.
Bibcode: 1998JGR...103.4715M
Altcode:
  The first mass-discriminated, hot ion distribution moments (pressure,
  energy intensity) are determined for hot &gt;50-keV ions in Jupiter's
  inner magnetosphere at the outer edge of Io's plasma torus by using
  the Galileo energetic particle detector (EPD) data. These hot plasmas
  were significantly depleted during the Galileo encounter in 1995 as
  compared with the Voyager epoch of 1979. The depletion of the hot ions
  is apparently caused by enhanced charge exchange losses of hot ions,
  perhaps associated with enhanced emissions of neutral gases from the
  volcanoes of Io. Such neutral gas enhancements could simultaneously
  explain increases, reported elsewhere, in the densities of the cooler Io
  torus plasmas. The hot plasma changes may explain why radial transport
  interchange turbulence has been observed by Galileo in the Io torus
  regions, whereas such turbulence was not apparent during the Voyager
  encounters in 1979. The hot ion depletion could also play a role
  in explaining the apparent differences between the Jovian auroral
  configuration observed in recent years by the Hubble space telescope
  and ground observers and the configuration observed by Voyager. This
  possibility is much less certain, however.

Title: The Energetic Particles Detector (EPD) aboard the Galileo
Spacecraft: First Results in the Jovian Magnetosphere
Authors: Krupp, N.; Lagg, A.; Livi, S.; Wilken, B.; Woch, J.; Williams,
   D. J.
Bibcode: 1997ASSL..220..319K
Altcode: 1997tgms.conf..319K
  No abstract at ADS

