Author name code: degroof
ADS astronomy entries on 2022-09-14
author:"De Groof, Anik" 
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Title: Solar Orbiter's first close encounter with the Sun: preparation
    of the coordinated science campaigns
Authors: de Groof, Anik; Müller, Daniel; Zouganelis, Yannis; Walsh,
   Andrew; Williams, David
Bibcode: 2022cosp...44.1537D
Altcode:
  After a Cruise Phase of 21 months, Solar Orbiter entered its first
  scientific orbit on 27 November 2021 after a Gravity Assist Manoeuvre
  (GAM) by the Earth. The spacecraft entered a highly elliptical orbit
  that will bring it up to its first close perihelion on 17 March 2022,
  at 0.32AU from the Sun. In the following years, further GAMs by Venus
  will lead it even closer to the Sun and also out of the ecliptic
  plane. Solar Orbiter's main goal is to study the connection between
  the solar activity close to the star's surface and its effects as seen
  in the heliosphere, the bubble-like region of space under the Sun's
  influence including all solar planets. Therefore, its main scientific
  goals can only be achieved by coordinated observations of both the
  6 remote-sensing telescopes onboard, observing the dynamic Sun, and
  the 4 in-situ instruments measuring the effects in the solar wind
  surrounding the spacecraft. This coordination takes careful planning
  and optimisation of the mission resources, in order to fully exploit
  the capabilities of this exciting mission. In this contribution,
  we present the science operations as planned for the first year of
  Nominal mission phase, i.e. the first two orbits. By the time of the
  COSPAR meeting, Solar Orbiter will have made its first close encounter
  and most of the data from the perihelion will have arrived!

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: Coordination of the in situ payload of Solar Orbiter
Authors: Walsh, A. P.; Horbury, T. S.; Maksimovic, M.; Owen, C. J.;
   Rodríguez-Pacheco, J.; Wimmer-Schweingruber, R. F.; Zouganelis,
   I.; Anekallu, C.; Bonnin, X.; Bruno, R.; Carrasco Blázquez, I.;
   Cernuda, I.; Chust, T.; De Groof, A.; Espinosa Lara, F.; Fazakerley,
   A. N.; Gilbert, H. R.; Gómez-Herrero, R.; Ho, G. C.; Krucker,
   S.; Lepri, S. T.; Lewis, G. R.; Livi, S.; Louarn, P.; Müller, D.;
   Nieves-Chinchilla, T.; O'Brien, H.; Osuna, P.; Plasson, P.; Raines,
   J. M.; Rouillard, A. P.; St Cyr, O. C.; Sánchez, L.; Soucek, J.;
   Varsani, A.; Verscharen, D.; Watson, C. J.; Watson, G.; Williams, D. R.
Bibcode: 2020A&A...642A...5W
Altcode:
  Solar Orbiter's in situ coordination working group met frequently
  during the development of the mission with the goal of ensuring
  that its in situ payload has the necessary level of coordination to
  maximise science return. Here we present the results of that work,
  namely how the design of each of the in situ instruments (EPD, MAG,
  RPW, SWA) was guided by the need for coordination, the importance of
  time synchronisation, and how science operations will be conducted
  in a coordinated way. We discuss the mechanisms by which instrument
  sampling schemes are aligned such that complementary measurements
  will be made simultaneously by different instruments, and how burst
  modes are scheduled to allow a maximum overlap of burst intervals
  between the four instruments (telemetry constraints mean different
  instruments can spend different amounts of time in burst mode). We
  also explain how onboard autonomy, inter-instrument communication,
  and selective data downlink will be used to maximise the number of
  transient events that will be studied using high-resolution modes of
  all the instruments. Finally, we briefly address coordination between
  Solar Orbiter's in situ payload and other missions.

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 Solar Orbiter SPICE instrument. An extreme UV imaging
    spectrometer
Authors: SPICE Consortium; Anderson, M.; Appourchaux, T.; Auchère, F.;
   Aznar Cuadrado, R.; Barbay, J.; Baudin, F.; Beardsley, S.; Bocchialini,
   K.; Borgo, B.; Bruzzi, D.; Buchlin, E.; Burton, G.; Büchel, V.;
   Caldwell, M.; Caminade, S.; Carlsson, M.; Curdt, W.; Davenne, J.;
   Davila, J.; Deforest, C. E.; Del Zanna, G.; Drummond, D.; Dubau,
   J.; Dumesnil, C.; Dunn, G.; Eccleston, P.; Fludra, A.; Fredvik, T.;
   Gabriel, A.; Giunta, A.; Gottwald, A.; Griffin, D.; Grundy, T.; Guest,
   S.; Gyo, M.; Haberreiter, M.; Hansteen, V.; Harrison, R.; Hassler,
   D. M.; Haugan, S. V. H.; Howe, C.; Janvier, M.; Klein, R.; Koller,
   S.; Kucera, T. A.; Kouliche, D.; Marsch, E.; Marshall, A.; Marshall,
   G.; Matthews, S. A.; McQuirk, C.; Meining, S.; Mercier, C.; Morris,
   N.; Morse, T.; Munro, G.; Parenti, S.; Pastor-Santos, C.; Peter, H.;
   Pfiffner, D.; Phelan, P.; Philippon, A.; Richards, A.; Rogers, K.;
   Sawyer, C.; Schlatter, P.; Schmutz, W.; Schühle, U.; Shaughnessy,
   B.; Sidher, S.; Solanki, S. K.; Speight, R.; Spescha, M.; Szwec, N.;
   Tamiatto, C.; Teriaca, L.; Thompson, W.; Tosh, I.; Tustain, S.; Vial,
   J. -C.; Walls, B.; Waltham, N.; Wimmer-Schweingruber, R.; Woodward,
   S.; Young, P.; de Groof, A.; Pacros, A.; Williams, D.; Müller, D.
Bibcode: 2020A&A...642A..14S
Altcode: 2019arXiv190901183A; 2019arXiv190901183S
  <BR /> Aims: The Spectral Imaging of the Coronal Environment (SPICE)
  instrument is a high-resolution imaging spectrometer operating at
  extreme ultraviolet wavelengths. In this paper, we present the concept,
  design, and pre-launch performance of this facility instrument on the
  ESA/NASA Solar Orbiter mission. <BR /> Methods: The goal of this paper
  is to give prospective users a better understanding of the possible
  types of observations, the data acquisition, and the sources that
  contribute to the instrument's signal. <BR /> Results: The paper
  discusses the science objectives, with a focus on the SPICE-specific
  aspects, before presenting the instrument's design, including optical,
  mechanical, thermal, and electronics aspects. This is followed by a
  characterisation and calibration of the instrument's performance. The
  paper concludes with descriptions of the operations concept and data
  processing. <BR /> Conclusions: The performance measurements of the
  various instrument parameters meet the requirements derived from the
  mission's science objectives. The SPICE instrument is ready to perform
  measurements that will provide vital contributions to the scientific
  success of the Solar Orbiter mission.

Title: Understanding the origins of the heliosphere: integrating
    observations and measurements from Parker Solar Probe, Solar Orbiter,
    and other space- and ground-based observatories
Authors: Velli, M.; Harra, L. K.; Vourlidas, A.; Schwadron,
   N.; Panasenco, O.; Liewer, P. C.; Müller, D.; Zouganelis, I.;
   St Cyr, O. C.; Gilbert, H.; Nieves-Chinchilla, T.; 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.; Wimmer-Schweingruber, R. F.; Bale, S.; Kasper,
   J.; McComas, D. J.; Raouafi, N.; Martinez-Pillet, V.; Walsh, A. P.;
   De Groof, A.; Williams, D.
Bibcode: 2020A&A...642A...4V
Altcode:
  Context. The launch of Parker Solar Probe (PSP) in 2018, followed
  by Solar Orbiter (SO) in February 2020, has opened a new window in
  the exploration of solar magnetic activity and the origin of the
  heliosphere. These missions, together with other space observatories
  dedicated to solar observations, such as the Solar Dynamics Observatory,
  Hinode, IRIS, STEREO, and SOHO, with complementary in situ observations
  from WIND and ACE, and ground based multi-wavelength observations
  including the DKIST observatory that has just seen first light,
  promise to revolutionize our understanding of the solar atmosphere
  and of solar activity, from the generation and emergence of the Sun's
  magnetic field to the creation of the solar wind and the acceleration of
  solar energetic particles. <BR /> Aims: Here we describe the scientific
  objectives of the PSP and SO missions, and highlight the potential for
  discovery arising from synergistic observations. Here we put particular
  emphasis on how the combined remote sensing and in situ observations of
  SO, that bracket the outer coronal and inner heliospheric observations
  by PSP, may provide a reconstruction of the solar wind and magnetic
  field expansion from the Sun out to beyond the orbit of Mercury in the
  first phases of the mission. In the later, out-of-ecliptic portions of
  the SO mission, the solar surface magnetic field measurements from SO
  and the multi-point white-light observations from both PSP and SO will
  shed light on the dynamic, intermittent solar wind escaping from helmet
  streamers, pseudo-streamers, and the confined coronal plasma, and on
  solar energetic particle transport. <BR /> Methods: Joint measurements
  during PSP-SO alignments, and magnetic connections along the same
  flux tube complemented by alignments with Earth, dual PSP-Earth,
  and SO-Earth, as well as with STEREO-A, SOHO, and BepiColumbo will
  allow a better understanding of the in situ evolution of solar-wind
  plasma flows and the full three-dimensional distribution of the
  solar wind from a purely observational point of view. Spectroscopic
  observations of the corona, and optical and radio observations,
  combined with direct in situ observations of the accelerating solar
  wind will provide a new foundation for understanding the fundamental
  physical processes leading to the energy transformations from solar
  photospheric flows and magnetic fields into the hot coronal plasma
  and magnetic fields and finally into the bulk kinetic energy of the
  solar wind and solar energetic particles. <BR /> Results: We discuss
  the initial PSP observations, which already provide a compelling
  rationale for new measurement campaigns by SO, along with ground-
  and space-based assets within the synergistic context described above.

Title: The Solar Orbiter mission. Science overview
Authors: Müller, D.; St. Cyr, O. C.; Zouganelis, I.; Gilbert, H. R.;
   Marsden, R.; Nieves-Chinchilla, T.; Antonucci, E.; Auchère, F.;
   Berghmans, D.; Horbury, T. S.; Howard, R. A.; Krucker, S.; Maksimovic,
   M.; Owen, C. J.; Rochus, P.; Rodriguez-Pacheco, J.; Romoli, M.;
   Solanki, S. K.; Bruno, R.; Carlsson, M.; Fludra, A.; Harra, L.;
   Hassler, D. M.; Livi, S.; Louarn, P.; Peter, H.; Schühle, U.;
   Teriaca, L.; del Toro Iniesta, J. C.; Wimmer-Schweingruber, R. F.;
   Marsch, E.; Velli, M.; De Groof, A.; Walsh, A.; Williams, D.
Bibcode: 2020A&A...642A...1M
Altcode: 2020arXiv200900861M
  <BR /> Aims: Solar Orbiter, the first mission of ESA's Cosmic Vision
  2015-2025 programme and a mission of international collaboration between
  ESA and NASA, will explore the Sun and heliosphere from close up and
  out of the ecliptic plane. It was launched on 10 February 2020 04:03
  UTC from Cape Canaveral and aims to address key questions of solar and
  heliospheric physics pertaining to how the Sun creates and controls
  the Heliosphere, and why solar activity changes with time. To answer
  these, the mission carries six remote-sensing instruments to observe
  the Sun and the solar corona, and four in-situ instruments to measure
  the solar wind, energetic particles, and electromagnetic fields. In
  this paper, we describe the science objectives of the mission, and how
  these will be addressed by the joint observations of the instruments
  onboard. <BR /> Methods: The paper first summarises the mission-level
  science objectives, followed by an overview of the spacecraft and
  payload. We report the observables and performance figures of each
  instrument, as well as the trajectory design. This is followed by a
  summary of the science operations concept. The paper concludes with a
  more detailed description of the science objectives. <BR /> Results:
  Solar Orbiter will combine in-situ measurements in the heliosphere
  with high-resolution remote-sensing observations of the Sun to address
  fundamental questions of solar and heliospheric physics. The performance
  of the Solar Orbiter payload meets the requirements derived from the
  mission's science objectives. Its science return will be augmented
  further by coordinated observations with other space missions and
  ground-based observatories. <P />ARRAY(0x207ce98)

Title: Solar Orbiter's Science Activity Plan: Translating Questions
    into Action
Authors: Zouganelis, Y.; Mueller, D.; De Groof, A.; Walsh, A. P.;
   Williams, D.
Bibcode: 2019AGUFMSH21D3315Z
Altcode:
  Solar Orbiter is a mission, scheduled for launch in February 2020,
  with as main goal to observe solar activity from close by, both in and
  out of the ecliptic, and to link it to the solar wind as sensed by its
  in-situ sensors. The payload consists of 6 remote-sensing and 4 in-situ
  instrument suites, which will have to coordinate their operations in
  order to address the four mission objectives: (1) What drives the solar
  wind and where does the heliospheric 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? We have to consider, however, that
  each orbit around the Sun has different characteristics, including the
  relative positions of the Earth and spacecraft (affecting downlink
  rates and communications blackouts), trajectory events (such as
  gravitational assist manoeuvres), and the phase of the solar activity
  cycle. Furthermore, each orbit's science telemetry will be downloaded
  during the next, so orbits cannot be planned individually. So how
  will those science questions be translated into an actual plan of
  observations that will fit into the mission? First, the component
  questions are broken down into answerable questions along with the
  observations they need from the payload. Then, in order to address this,
  the so-called Science Activity Plan (SAP) has been developed. The
  SAP groups together objectives that require similar observations
  into Solar Orbiter Observing Plans (SOOPs), resulting in a strategic,
  top-level view of the optimal opportunities for science observations
  across the mission lifetime, allowing all four mission objectives to
  be addressed. In this presentation, we introduce Solar Orbiter's SAP
  through a series of examples and the strategy being followed.

Title: An Unusual Widespread Solar Energetic Particle Event
Authors: Rodriguez-Garcia, L.; Gomez-Herrero, R.; Zouganelis, Y.;
   Rodriguez-Pacheco, J.; Dresing, N.; Williams, D.; De Groof, A.
Bibcode: 2019AGUFMSH23C3355R
Altcode:
  Over the course of several hours, a Solar Energetic Particle (SEP) event
  was observed by the twin spacecraft of the Solar TErrestrial RElations
  Observatory (STEREO A and B), by several near-Earth spacecraft like the
  SOlar and Heliospheric Observatory (SOHO), and by the MErcury Surface,
  Space ENvironment, GEochemistry and Ranging (MESSENGER) in orbit around
  Mercury. These multiple observation points covered a considerable
  angular span of 222 degrees in the ecliptic plane. The widespread SEP
  event was associated with a halo Coronal Mass Ejection (CME) passing
  through the SOHO/ Large Angle and Spectrometric Coronagraph ( LASCO)
  field of view, with a plane-of-sky speed of 877 km/s. The CME was
  accompanied by type III and type II radio bursts but, surprisingly ,
  in spite of the 360 degree remote-sensing coverage of the solar disk
  at different wavelengths, no major solar flare was observed. The SEP
  event showed a very gradual rise of particle intensities at STEREO-A,
  STEREO-B and the Earth, and the particle onset at STEREO-B and the
  Earth were delayed by several hours with respect to the estimated
  lift-off time of the CME. Unexpectedly, this was also the case for
  STEREO-A, relatively well connected to the source. However, MESSENGER,
  located closer to the Sun and slightly better connected to the source
  than STEREO-A, observed a clear electron increase with much shorter
  temporal delay. It is remarkable that all the spacecraft-observed
  electron increases approach relativistic energies and proton increases
  reach energies beyond 50 MeV. To disentangle the possible scenarios for
  particle acceleration and propagation during this unusual widespread
  SEP event, particles anisotropies, onset-timing dispersion and act ive
  r egion m agnetic foot-point separation are discussed. To understand
  their possible effect on the SEP interplanetary propagation conditions,
  the identification and 3D geometric characterisation of the CME, as
  well as of previously ejected Interplanetary Coronal Mass Ejections
  (ICME) and shocks, are analysed. Different physical scenarios explaining
  the wide spread of the SEP such as, a wide coronal shock, cross-field
  diffusion and particle confinement in the interplanetary medium are
  discussed and compared with the observational signatures.

Title: Solar Orbiter Science Operations: Not A Typical Heliophysics
    Mission
Authors: Walsh, A. P.; De Groof, A.; Williams, D.; Sánchez, L.;
   Zouganelis, Y.
Bibcode: 2019AGUFMSH21D3314W
Altcode:
  ESA's Solar Orbiter is scheduled for launch in February 2020, and will
  approach the Sun to a distance of 0.28 AU, in an orbit progressively
  more inclined to the Ecliptic plane. Solar Orbiter will provide
  landmark new views of a star, up-close, often observing its poles,
  while measuring the coupling of the solar phenomena and features to
  the relatively pristine solar wind that it will measure in situ. The
  unique orbit of the spacecraft and the arrangement and composition of
  its scientific payload impose unique constraints on how scientific
  operations can be conducted. These operations involve long- to very
  short-term planning in carefully arranged steps, which have much more
  in common with planetary encounter missions than preceding heliophysics
  missions. In this presentation, we explain the details of how science
  observations will be arranged and conducted, often very far from Earth,
  and how data from the mission will be returned and distributed.

Title: The Energy Spectrum of the Solar Wind Core
Authors: Walsh, A. P.; Toledo Redondo, S.; Osuna, P.; Zouganelis,
   Y.; Masson, A.; De Groof, A.; Perrone, D.; Roberts, O. W.; Taylor, M.
Bibcode: 2017AGUFMSH23D2685W
Altcode:
  The solar wind electron distribution is typically characterised
  as having three components, a broadly isotropic core at the lowest
  energies, an isotropic halo at higher energies and a field-aligned
  strahl at energies similar to those of the halo. Historically,
  the core has been described by a Maxwellian distribution function
  while the halo and strahl are known to be suprathermal and have been
  described using kappa functions. We use high energy resolution Cluster
  PEACE measurements to re-examine the spectral shape of the observed
  distributions at core energies and find that, at least some of the time,
  a kappa function better describes them than a Maxwellian. During these
  times, no spectral break is found at typical halo energies. We discuss
  the causes and implications of this in the context of Solar Orbiter
  and Parker Solar Probe.

Title: Performances of swap on-board PROBA-2
Authors: Halain, J. -P.; Berghmans, D.; Defise, J. -F.; Rochus, P.;
   Nicula, B.; de Groof, A.; Seaton, D.
Bibcode: 2017SPIE10565E..0SH
Altcode:
  The PROBA2 mission has been launched on 2nd November2009 with a Rockot
  launcher to a Sunsynchronous orbit at an altitude of 725 km. Its
  nominal operation duration is two years with possible extension of
  2 years. PROBA2 is a small satellite developed under an ESA General
  Support Technology Program (GSTP) contract to perform an in-flight
  demonstration of new space technologies and support a scientific
  mission for a set of selected instruments. The mission is tracked by
  the ESA Redu Mission Operation Center.

Title: Solar Orbiter Science Operations: Not A Typical Heliophysics
    Mission
Authors: Williams, David R.; De Groof, Anik; Walsh, Andrew
Bibcode: 2017SPD....4811408W
Altcode:
  ESA’s Solar Orbiter is scheduled for launch in February 2019, and will
  approach the Sun to a distance of 0.28 AU, in an orbit progressively
  more inclined to the Ecliptic plane. Solar Orbiter will provide
  landmark new views of a star, up-close, often observing its poles,
  while measuring the coupling of the solar phenomena and features
  to the relatively pristine solar wind that it measure in situ. The
  unique orbit of the spacecraft and the arrangement and composition of
  its scientific payload impose unique constraints on how scientific
  operations can be conducted. These operations involve long- to very
  short-term planning in carefully arranged steps, which have much in
  common with planetary-encounter missions than preceding heliophysics
  missions. In this presentation, we explain the details of how science
  observations will be arranged and conducted, often very far from Earth,
  and how data from the mission will be returned and distributed.

Title: Solar signatures and eruption mechanism of the August 14,
    2010 coronal mass ejection (CME)
Authors: D'Huys, Elke; Seaton, Daniel B.; De Groof, Anik; Berghmans,
   David; Poedts, Stefaan
Bibcode: 2017JSWSC...7A...7D
Altcode: 2017arXiv170108814D
  On August 14, 2010 a wide-angled coronal mass ejection (CME) was
  observed. This solar eruption originated from a destabilized filament
  that connected two active regions and the unwinding of this filament
  gave the eruption an untwisting motion that drew the attention
  of many observers. In addition to the erupting filament and the
  associated CME, several other low-coronal signatures that typically
  indicate the occurrence of a solar eruption were associated with this
  event. However, contrary to what was expected, the fast CME (v &gt;
  900 km s<SUP>-1</SUP>) was accompanied by only a weak C4.4 flare. We
  investigate the various eruption signatures that were observed for this
  event and focus on the kinematic evolution of the filament in order to
  determine its eruption mechanism. Had this solar eruption occurred just
  a few days earlier, it could have been a significant event for space
  weather. The risk of underestimating the strength of this eruption based
  solely on the C4.4 flare illustrates the need to include all eruption
  signatures in event analyses in order to obtain a complete picture of
  a solar eruption and assess its possible space weather impact.

Title: Solar Wind Core Electrons: Kappa or Maxwellian?
Authors: Walsh, A. P.; Osuna, P.; Toledo Redondo, S.; Zouganelis, Y.;
   Masson, A.; De Groof, A.; Mueller, D.; Perrone, D.; Roberts, O. W.;
   Taylor, M. G.; Turc, L.
Bibcode: 2016AGUFMSH51D2608W
Altcode:
  Solar wind core electrons are typically considered to have a Maxwellian
  velocity distribution function. However, most measurements made of
  them to date don't have sufficient energy resolution to distinguish
  between a Maxwellian and a kappa distribution at low energies. Here
  we present a survey of solar wind electron velocity distribution
  functions observed by Cluster PEACE in its highest energy resolution
  mode, which is sufficient to distinguish between Maxwellian and kappa
  distributions for energies below 15eV. Initial results suggest that a
  kappa distribution better fits the data than a Maxwellian in all cases;
  in the majority of cases the difference in goodness of fit between a
  kappa and Maxwellian is small but in some cases, a kappa distribution
  fits the data significantly better.

Title: A virtual appliance as proxy pipeline for the Solar
    Orbiter/Metis coronagraph
Authors: Pancrazzi, M.; Straus, T.; Andretta, V.; Spadaro, D.; Haugan,
   S. V.; de Groof, A.; Carr, R.; Focardi, M.; Nicolini, G.; Landini,
   F.; Baccani, C.; Romoli, M.; Antonucci, E.
Bibcode: 2016SPIE.9913E..4LP
Altcode:
  Metis is the coronagraph on board Solar Orbiter, the ESA mission devoted
  to the study of the Sun that will be launched in October 2018. Metis is
  designed to perform imaging of the solar corona in the UV at 121.6 nm
  and in the visible range where it will accomplish polarimetry studies
  thanks to a variable retarder plate. Due to mission constraints, the
  telemetry downlink on the spacecraft will be limited and data will be
  downloaded with delays that could reach, in the worst case, several
  months. In order to have a quick overview on the ongoing operations
  and to check the safety of the 10 instruments on board, a high-priority
  downlink channel has been foreseen to download a restricted amount of
  data. These so-called Low Latency Data will be downloaded daily and,
  since they could trigger possible actions, they have to be quickly
  processed on ground as soon as they are delivered. To do so, a proper
  processing pipeline has to be developed by each instrument. This
  tool will then be integrated in a single system at the ESA Science
  Operation Center that will receive the downloaded data by the Mission
  Operation Center. This paper will provide a brief overview of the on
  board processing and data produced by Metis and it will describe the
  proxy-pipeline currently under development to deal with the Metis
  low-latency data.

Title: PROBA2/SWAP EUV images of the large-scale EUV corona up to 3
solar radii: Can we close the gap in coronal magnetic field structure
    between 1.3 and 2.5 solar radii?
Authors: De Groof, Anik; Seaton, Daniel B.; Rachmeler, Laurel;
   Berghmans, David
Bibcode: 2015TESS....140901D
Altcode:
  The EUV telescope PROBA2/SWAP has been observing the solar corona in
  a bandpass near 17.4 nm since February 2010. SWAP's wide field-of-view
  provides a unique and continuous view of the extended EUV corona up to
  2-3 solar radii. By carefully processing and combining multiple SWAP
  images, low-noise composites were produced that reveal large-scale,
  EUV-emitting, coronal structures. These extended structures appear
  mainly above or at the edges of active regions and typically curve
  towards the poles. As they persist for multiple Carrington rotations
  and cannot easily be related to white-light features, they give an
  interesting view on how the coronal magnetic field is structured
  between 1.3 and 2-3 solar radii, in the gap between SDO/AIA’s FOV
  and typical lower boundaries of coronagraph FOVs. With the help of
  magnetic field models, we analyse the geometry of the extended EUV
  structures in more detail and compare with sporadic EUV coronagraph
  measurements up to as close as 1.5Rs. The opportunities that Solar
  Orbiter’s future observations will bring are explored.

Title: SWAP Observations of the Long-term, Large-scale Evolution of
    the Extreme-ultraviolet Solar Corona
Authors: Seaton, Daniel B.; De Groof, Anik; Shearer, Paul; Berghmans,
   David; Nicula, Bogdan
Bibcode: 2013ApJ...777...72S
Altcode: 2013arXiv1309.1345S
  The Sun Watcher with Active Pixels and Image Processing (SWAP) EUV solar
  telescope on board the Project for On-Board Autonomy 2 spacecraft has
  been regularly observing the solar corona in a bandpass near 17.4 nm
  since 2010 February. With a field of view of 54 × 54 arcmin, SWAP
  provides the widest-field images of the EUV corona available from
  the perspective of the Earth. By carefully processing and combining
  multiple SWAP images, it is possible to produce low-noise composites
  that reveal the structure of the EUV corona to relatively large
  heights. A particularly important step in this processing was to remove
  instrumental stray light from the images by determining and deconvolving
  SWAP's point-spread function from the observations. In this paper,
  we use the resulting images to conduct the first-ever study of the
  evolution of the large-scale structure of the corona observed in the
  EUV over a three year period that includes the complete rise phase of
  solar cycle 24. Of particular note is the persistence over many solar
  rotations of bright, diffuse features composed of open magnetic fields
  that overlie polar crown filaments and extend to large heights above
  the solar surface. These features appear to be related to coronal fans,
  which have previously been observed in white-light coronagraph images
  and, at low heights, in the EUV. We also discuss the evolution of the
  corona at different heights above the solar surface and the evolution
  of the corona over the course of the solar cycle by hemisphere.

Title: The SWAP EUV Imaging Telescope Part I: Instrument Overview
    and Pre-Flight Testing
Authors: Seaton, D. B.; Berghmans, D.; Nicula, B.; Halain, J. -P.; De
   Groof, A.; Thibert, T.; Bloomfield, D. S.; Raftery, C. L.; Gallagher,
   P. T.; Auchère, F.; Defise, J. -M.; D'Huys, E.; Lecat, J. -H.; Mazy,
   E.; Rochus, P.; Rossi, L.; Schühle, U.; Slemzin, V.; Yalim, M. S.;
   Zender, J.
Bibcode: 2013SoPh..286...43S
Altcode: 2012SoPh..tmp..217S; 2012arXiv1208.4631S
  The Sun Watcher with Active Pixels and Image Processing (SWAP) is
  an EUV solar telescope onboard ESA's Project for Onboard Autonomy 2
  (PROBA2) mission launched on 2 November 2009. SWAP has a spectral
  bandpass centered on 17.4 nm and provides images of the low solar
  corona over a 54×54 arcmin field-of-view with 3.2 arcsec pixels and
  an imaging cadence of about two minutes. SWAP is designed to monitor
  all space-weather-relevant events and features in the low solar
  corona. Given the limited resources of the PROBA2 microsatellite,
  the SWAP telescope is designed with various innovative technologies,
  including an off-axis optical design and a CMOS-APS detector. This
  article provides reference documentation for users of the SWAP image
  data.

Title: Preface
Authors: Berghmans, D.; De Groof, A.; Dominique, M.; Hochedez, J. -F.;
   Leibacher, J. W.
Bibcode: 2013SoPh..286....1B
Altcode:
  No abstract at ADS

Title: SoFAST: Automated Flare Detection with the PROBA2/SWAP
    EUV Imager
Authors: Bonte, K.; Berghmans, D.; De Groof, A.; Steed, K.; Poedts, S.
Bibcode: 2013SoPh..286..185B
Altcode: 2012SoPh..tmp..288B
  The Sun Watcher with Active Pixels and Image Processing (SWAP)
  EUV imager onboard PROBA2 provides a non-stop stream of coronal
  extreme-ultraviolet (EUV) images at a cadence of typically 130
  seconds. These images show the solar drivers of space-weather, such
  as flares and erupting filaments. We have developed a software tool
  that automatically processes the images and localises and identifies
  flares. On one hand, the output of this software tool is intended
  as a service to the Space Weather Segment of ESA's Space Situational
  Awareness (SSA) program. On the other hand, we consider the PROBA2/SWAP
  images as a model for the data from the Extreme Ultraviolet Imager (EUI)
  instrument prepared for the future Solar Orbiter mission, where onboard
  intelligence is required for prioritising data within the challenging
  telemetry quota. In this article we present the concept of the software,
  the first statistics on its effectiveness and the online display in
  real time of its results. Our results indicate that it is not only
  possible to detect EUV flares automatically in an acquired dataset,
  but that quantifying a range of EUV dynamics is also possible. The
  method is based on thresholding of macropixelled image sequences. The
  robustness and simplicity of the algorithm is a clear advantage for
  future onboard use.

Title: The Projects for Onboard Autonomy (PROBA2) Science Centre:
    Sun Watcher Using APS Detectors and Image Processing (SWAP) and
    Large-Yield Radiometer (LYRA) Science Operations and Data Products
Authors: Zender, J.; Berghmans, D.; Bloomfield, D. S.; Cabanas Parada,
   C.; Dammasch, I.; De Groof, A.; D'Huys, E.; Dominique, M.; Gallagher,
   P.; Giordanengo, B.; Higgins, P. A.; Hochedez, J. -F.; Yalim, M. S.;
   Nicula, B.; Pylyser, E.; Sanchez-Duarte, L.; Schwehm, G.; Seaton,
   D. B.; Stanger, A.; Stegen, K.; Willems, S.
Bibcode: 2013SoPh..286...93Z
Altcode: 2012SoPh..tmp..142Z
  The PROBA2 Science Centre (P2SC) is a small-scale science operations
  centre supporting the Sun observation instruments onboard PROBA2:
  the EUV imager Sun Watcher using APS detectors and image Processing
  (SWAP) and Large-Yield Radiometer (LYRA). PROBA2 is one of ESA's
  small, low-cost Projects for Onboard Autonomy (PROBA) and part of
  ESA's In-Orbit Technology Demonstration Programme. The P2SC is hosted
  at the Royal Observatory of Belgium, co-located with both Principal
  Investigator teams. The P2SC tasks cover science planning, instrument
  commanding, instrument monitoring, data processing, support of outreach
  activities, and distribution of science data products. PROBA missions
  aim for a high degree of autonomy at mission and system level, including
  the science operations centre. The autonomy and flexibility of the P2SC
  is reached by a set of web-based interfaces allowing the operators as
  well as the instrument teams to monitor quasi-continuously the status of
  the operations, allowing a quick reaction to solar events. In addition,
  several new concepts are implemented at instrument, spacecraft, and
  ground-segment levels allowing a high degree of flexibility in the
  operations of the instruments. This article explains the key concepts
  of the P2SC, emphasising the automation and the flexibility achieved
  in the commanding as well as the data-processing chain.

Title: Temperature Response of the 171 Å Passband of the SWAP Imager
    on PROBA2, with a Comparison to TRACE, SOHO, STEREO, and SDO
Authors: Raftery, Claire L.; Bloomfield, D. Shaun; Gallagher, Peter
   T.; Seaton, Daniel B.; Berghmans, David; De Groof, Anik
Bibcode: 2013SoPh..286..111R
Altcode:
  We calculated the temperature response of the 171 Å passbands of
  the Sun Watcher using APS detectors and image Processing (SWAP)
  instrument onboard the PRoject for OnBoard Autonomy 2 (PROBA2)
  satellite. These results were compared to the temperature responses
  of the Extreme Ultraviolet Imaging Telescope (EIT) onboard the Solar
  and Heliospheric Observatory (SOHO), the Transition Region and Coronal
  Explorer (TRACE), the twin Extreme Ultraviolet Imagers (EUVI) onboard
  the Solar TErrestrial RElations Observatory (STEREO) A and B spacecraft,
  and the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics
  Observatory (SDO). Multiplying the wavelength-response functions
  for each instrument by a series of isothermal synthetic spectra and
  integrating over the range 165 - 195 Å produced temperature-response
  functions for the six instruments. Each temperature response was
  then multiplied by sample differential emission-measure functions
  for four different solar conditions. For any given plasma condition
  (e.g. quiet Sun, active region), it was found that the overall variation
  with temperature agreed remarkably well across the six instruments,
  although the wavelength responses for each instrument have some
  distinctly different features. Deviations were observed, however,
  when we compared the response of any one instrument to different solar
  conditions, particularly for the case of solar flares.

Title: The SWAP EUV Imaging Telescope. Part II: In-flight Performance
    and Calibration
Authors: Halain, J. -P.; Berghmans, D.; Seaton, D. B.; Nicula, B.;
   De Groof, A.; Mierla, M.; Mazzoli, A.; Defise, J. -M.; Rochus, P.
Bibcode: 2013SoPh..286...67H
Altcode: 2012SoPh..tmp..317H; 2012arXiv1210.3551H
  The Sun Watcher with Active Pixel System detector and Image
  Processing (SWAP) telescope was launched on 2 November 2009
  onboard the ESA PROBA2 technological mission and has acquired
  images of the solar corona every one to two minutes for more than
  two years. The most important technological developments included in
  SWAP are a radiation-resistant CMOS-APS detector and a novel onboard
  data-prioritization scheme. Although such detectors have been used
  previously in space, they have never been used for long-term scientific
  observations on orbit. Thus SWAP requires a careful calibration to
  guarantee the science return of the instrument. Since launch we have
  regularly monitored the evolution of SWAP's detector response in-flight
  to characterize both its performance and degradation over the course
  of the mission. These measurements are also used to reduce detector
  noise in calibrated images (by subtracting dark-current). Because
  accurate measurements of detector dark-current require large telescope
  off-points, we also monitored straylight levels in the instrument to
  ensure that these calibration measurements are not contaminated by
  residual signal from the Sun. Here we present the results of these
  tests and examine the variation of instrumental response and noise as
  a function of both time and temperature throughout the mission.

Title: PROBA2: Mission and Spacecraft Overview
Authors: Santandrea, S.; Gantois, K.; Strauch, K.; Teston, F.; Proba2
   Project Team; Tilmans, E.; Baijot, C.; Gerrits, D.; Proba2 Industry
   Team; de Groof, A.; Schwehm, G.; Zender, J.
Bibcode: 2013SoPh..286....5S
Altcode:
  Within the European Space Agency's (ESA) General Support and Technology
  Programme (GSTP), the Project for On-Board Autonomy (PROBA) missions
  provide a platform for in-orbit technology demonstration. Besides
  the technology demonstration goal, the satellites allow to provide
  services to, e.g., scientific communities. PROBA1 has been providing
  multi-spectral imaging data to the Earth observation community for a
  decade, and PROBA2 provides imaging and irradiance data from our Sun
  to the solar community. This article gives an overview of the PROBA2
  mission history and provides an introduction to the flight segment,
  the ground segment, and the payload operated onboard. Important aspects
  of the satellite's design, including onboard software autonomy and the
  functionality of the navigation and guidance, are discussed. PROBA2
  successfully proved again within the GSTP concept that it is possible
  to provide a fast and cost-efficient satellite design and to combine
  advanced technology objectives from industry with focussed objectives
  from the science community.

Title: Study of a Prominence Eruption using PROBA2/SWAP and
    STEREO/EUVI Data
Authors: Mierla, M.; Seaton, D. B.; Berghmans, D.; Chifu, I.; De Groof,
   A.; Inhester, B.; Rodriguez, L.; Stenborg, G.; Zhukov, A. N.
Bibcode: 2013SoPh..286..241M
Altcode: 2012SoPh..tmp...66M; 2012arXiv1203.6732M
  Observations of the early rise and propagation phases of solar eruptive
  prominences can provide clues about the forces acting on them through
  the behavior of their acceleration with height. We have analyzed such an
  event, observed on 13 April 2010 by SWAP on PROBA2 and EUVI on STEREO. A
  feature at the top of the erupting prominence was identified and tracked
  in images from the three spacecraft. The triangulation technique was
  used to derive the true direction of propagation of this feature. The
  reconstructed points were fitted with two mathematical models: i) a
  power-law polynomial function and ii) a cubic smoothing spline, in order
  to derive the accelerations. The first model is characterized by five
  degrees of freedom while the second one is characterized by ten degrees
  of freedom. The results show that the acceleration increases smoothly,
  and it is continuously increasing with height. We conclude that the
  prominence is not accelerated immediately by local reconnection,
  but rather is swept away as part of a large-scale relaxation of the
  coronal magnetic field.

Title: Solar TErrestrial Relations Observatory-A (STEREO-A) and
    PRoject for On-Board Autonomy 2 (PROBA2) Quadrature Observations of
    Reflections of Three EUV Waves from a Coronal Hole
Authors: Kienreich, I. W.; Muhr, N.; Veronig, A. M.; Berghmans, D.;
   De Groof, A.; Temmer, M.; Vršnak, B.; Seaton, D. B.
Bibcode: 2013SoPh..286..201K
Altcode: 2012SoPh..tmp..138K
  We investigate the interaction of three consecutive large-scale coronal
  waves with a polar coronal hole, simultaneously observed on-disk by the
  Solar TErrestrial Relations Observatory (STEREO)-A spacecraft and on
  the limb by the PRoject for On-Board Autonomy 2 (PROBA2) spacecraft on
  27 January 2011. All three extreme ultraviolet (EUV) waves originate
  from the same active region, NOAA 11149, positioned at N30E15 in the
  STEREO-A field of view and on the limb in PROBA2. For the three primary
  EUV waves, we derive starting velocities in the range of ≈ 310 km
  s<SUP>−1</SUP> for the weakest up to ≈ 500 km s<SUP>−1</SUP>
  for the strongest event. Each large-scale wave is reflected at the
  border of the extended coronal hole at the southern polar region. The
  average velocities of the reflected waves are found to be smaller than
  the mean velocities of their associated direct waves. However, the
  kinematical study also reveals that in each case the ending velocity
  of the primary wave matches the initial velocity of the reflected
  wave. In all three events, the primary and reflected waves obey the
  Huygens-Fresnel principle, as the incident angle with ≈ 10° to
  the normal is of the same magnitude as the angle of reflection. The
  correlation between the speed and the strength of the primary EUV waves,
  the homologous appearance of both the primary and the reflected waves,
  and in particular the EUV wave reflections themselves suggest that the
  observed EUV transients are indeed nonlinear large-amplitude MHD waves.

Title: Quasi-Periodic Pulsations during the onset of solar flares:
    multi-instrumental comparison
Authors: West, M. J.; Dolla, L.; Marque, C.; Seaton, D. B.; Van
   Doorsselaere, T.; Dominique, M.; Berghmans, D.; Cabanas, C.; De Groof,
   A.; Schmutz, W.; Verdini, A.; Zender, J.; Zhukov, A. N.
Bibcode: 2013enss.confE..82W
Altcode:
  Quasi-periodic pulsations have been observed in the rising phase of
  solar flares for many years. Observations have been made over a wide
  spectral range, extending from X-rays to radio wavelengths. The
  current generation of spacebourne instruments, especially SDO,
  EVE and ESP, have exceptionally high sampling rates and allow us
  to make more detailed observations of this phenomena. In this work,
  we compare short-period oscillations (around 10 s) observed in flare
  events by multiple instruments: the radiometer channels of SDO/EVE-ESP
  (soft X-ray, coronal and chromospheric passbands), the EUV channels of
  the radiometer PROBA2/LYRA, the RHESSI passbands and short-wavelength
  radio observations.

Title: Plasmoid Ejection at a Solar Total Eclipse
Authors: Koutchmy, S.; Bazin, C.; Berghmans, D.; De Groof, A.;
   Druckmüller, M.; Tavabi, E.; Engell, A.; Filippov, B.; Golub, L.;
   Lamy, Ph.; Linker, J.; Mikic, Z.; Mouette, J.; Nitschelm, Ch.; Seaton,
   D.; Slemzin, V.
Bibcode: 2012EAS....55..223K
Altcode:
  The existence of coronal plasmoids has been postulated for many years
  in order to supply material to streamers and possibly to the solar
  wind (SW). The W-L SoHO C2 Lasco coronagraph observations were made
  under the 2.2 solar radii (R0) occulting disk to look at the ultimate
  sources of the SW; EUV imagers are preferably devoted to the analysis
  of the corona on and very near the solar disk. Here, in addition to
  eclipse white-light (W-L) snapshots, we used the new SWAP space-borne
  imager designed for the systematic survey of coronal activity in the
  EUV lines near 17.4 nm, over a field of view (FOV) up to 2 R0. Using
  summed and co-aligned images, the corona can then be evaluated for the
  1st time up to the limit of this FOV. At the time of the July 11, 2010,
  solar total eclipse a 20h continuous run of observations was collected,
  including images taken during eclipse totality from several ground
  observing locations where W-L data were collected. A plasmoid-like
  off-limb event was followed using the SWAP summed

Title: STEREO-A and PROBA2 Quadrature Observations of Reflections
    of three EUV Waves from a Coronal Hole
Authors: Kienreich, Ines Waltraud; Muhr, Nicole; Veronig, Astrid;
   Berghmans, David; de Groof, Anik; Temmer, Manuela; Vršnak, Bojan;
   Seaton, Dan
Bibcode: 2012arXiv1204.6472K
Altcode: 2012arXiv1204.6472W
  We investigate the interaction of three consecutive large-scale coronal
  waves with a polar coronal hole, simultaneously observed on-disk by the
  Solar TErrestrial Relations Observatory (STEREO)-A spacecraft and on
  the limb by the PRoject for On-Board Autonomy 2 (PROBA2) spacecraft on
  January 27, 2011. All three extreme-ultraviolet(EUV) waves originate
  from the same active region NOAA 11149 positioned at N30E15 in the
  STEREO-A field-of-view and on the limb in PROBA2. We derive for the
  three primary EUV waves start velocities in the range of ~310 km/s for
  the weakest up to ~500 km/s for the strongest event. Each large-scale
  wave is reflected at the border of the extended coronal hole at the
  southern polar region. The average velocities of the reflected waves
  are found to be smaller than the mean velocities of their associated
  direct waves. However, the kinematical study also reveals that in each
  case the end velocity of the primary wave matches the initial velocity
  of the reflected wave. In all three events the primary and reflected
  waves obey the Huygens-Fresnel principle, as the incident angle with
  ~10° to the normal is of the same size as the angle of reflection. The
  correlation between the speed and the strength of the primary EUV waves,
  the homologous appearance of both the primary and the reflected waves,
  and in particular the EUV wave reflections themselves implicate that the
  observed EUV transients are indeed nonlinear large-amplitude MHD waves.

Title: Time Delays in Quasi-periodic Pulsations Observed during the
    X2.2 Solar Flare on 2011 February 15
Authors: Dolla, L.; Marqué, C.; Seaton, D. B.; Van Doorsselaere,
   T.; Dominique, M.; Berghmans, D.; Cabanas, C.; De Groof, A.; Schmutz,
   W.; Verdini, A.; West, M. J.; Zender, J.; Zhukov, A. N.
Bibcode: 2012ApJ...749L..16D
Altcode: 2012arXiv1203.6223D
  We report observations of quasi-periodic pulsations (QPPs) during the
  X2.2 flare of 2011 February 15, observed simultaneously in several
  wavebands. We focus on fluctuations on timescale 1-30 s and find
  different time lags between different wavebands. During the impulsive
  phase, the Reuven Ramaty High Energy Solar Spectroscopic Imager
  channels in the range 25-100 keV lead all the other channels. They
  are followed by the Nobeyama RadioPolarimeters at 9 and 17 GHz and the
  extreme-ultraviolet (EUV) channels of the Euv SpectroPhotometer (ESP)
  on board the Solar Dynamic Observatory. The zirconium and aluminum
  filter channels of the Large Yield Radiometer on board the Project for
  On-Board Autonomy satellite and the soft X-ray (SXR) channel of ESP
  follow. The largest lags occur in observations from the Geostationary
  Operational Environmental Satellite, where the channel at 1-8 Å leads
  the 0.5-4 Å channel by several seconds. The time lags between the
  first and last channels is up to ≈9 s. We identified at least two
  distinct time intervals during the flare impulsive phase, during which
  the QPPs were associated with two different sources in the Nobeyama
  RadioHeliograph at 17 GHz. The radio as well as the hard X-ray channels
  showed different lags during these two intervals. To our knowledge,
  this is the first time that time lags are reported between EUV and
  SXR fluctuations on these timescales. We discuss possible emission
  mechanisms and interpretations, including flare electron trapping.

Title: LYRA and SWAP, the two Solar Instruments on-board PROBA2
Authors: Dominique, M.; Berghmans, D.; Schmutz, W. K.; Dammasch, I.;
   De Groof, A.; Halain, J.; Hochedez, J.; Kretzschmar, M.; Seaton, D. B.
Bibcode: 2011AGUFMSH13B1949D
Altcode:
  PROBA2 (http://proba2.sidc.be) is an ESA micro-satellite that was
  launched in November 2009. Two instruments on-board, SWAP and LYRA, are
  devoted to solar observations. SWAP (PI: D. Berghmans) is an EUV imager
  observing the corona with a bandpass centered on 174 Å at a cadence of
  1-2 min. Its high contrast images, large FOV and flexible off-pointing
  capabilities make SWAP particularly well suited for the study of coronal
  eruptions. LYRA (PI: M. Dominique) is a UV-EUV radiometer observing
  in four spectral channels, chosen for their relevance in solar physics
  and aeronomy. Its very fast acquisition cadence (up to 100 Hz) allows
  scientists to perform detailed analysis of solar flares. We discuss
  the characteristics of both instruments, review their performance and
  evolution, and highlight their complementarity to other missions. We
  also present the data products that can be downloaded from the mission
  website and give an overview of the various investigations for which
  SWAP and LYRA data are currently used (CMEs, flares, solar variability,
  and many others).

Title: LYRA Observations of Two Oscillation Modes in a Single Flare
Authors: Van Doorsselaere, T.; De Groof, A.; Zender, J.; Berghmans,
   D.; Goossens, M.
Bibcode: 2011ApJ...740...90V
Altcode:
  We analyze light curves from the LYRA irradiance experiment on
  board PROBA2 during the flare of 2010 February 8. We see both long-
  and short-period oscillations during the flare. The long-period
  oscillation is interpreted in terms of standing slow sausage modes;
  the short-period oscillation is thought to be a standing fast sausage
  mode. The simultaneous presence of two oscillation modes in the same
  flaring structure allows for new coronal seismological applications. The
  periods are used to find seismological estimates of the plasma-β and
  the density contrast of the flaring loop. Also the wave mode number
  is estimated from the observed periods.

Title: Validation of CME Detection Software (CACTus) by Means of
    Simulated Data, and Analysis of Projection Effects on CME Velocity
    Measurements
Authors: Bonte, K.; Jacobs, C.; Robbrecht, E.; De Groof, A.; Berghmans,
   D.; Poedts, S.
Bibcode: 2011SoPh..270..253B
Altcode: 2011SoPh..tmp...52B; 2011SoPh..tmp...72B
  In the context of space weather forecasting, an automated detection
  of coronal mass ejections (CMEs) becomes more and more important
  for efficiently handling a large data flow which is expected from
  recently-launched and future solar missions. In this paper we validate
  the detection software package "CACTus" by applying the program to
  synthetic data from our 3D time-dependent CME simulations instead of
  observational data. The main strength of this study is that we know
  in advance what should be detected. We describe the sensitivities
  and strengths of automated detection, more specific for the CACTus
  program, resulting in a better understanding of CME detection on one
  hand and the calibration of the CACTus software on the other hand,
  suggesting possible improvements of the package. In addition, the
  simulation is an ideal tool to investigate projection effects on CME
  velocity measurements.

Title: First light of SWAP on-board PROBA2
Authors: Halain, Jean-Philippe; Berghmans, David; Defise, Jean-Marc;
   Renotte, Etienne; Thibert, Tanguy; Mazy, Emmanuel; Rochus, Pierre;
   Nicula, Bogdan; de Groof, Anik; Seaton, Dan; Schühle, Udo
Bibcode: 2010SPIE.7732E..0PH
Altcode: 2010SPIE.7732E..18H
  The SWAP telescope (Sun Watcher using Active Pixel System detector
  and Image Processing) is an instrument launched on 2nd November 2009
  on-board the ESA PROBA2 technological mission. SWAP is a space weather
  sentinel from a low Earth orbit, providing images at 174 nm of the
  solar corona. The instrument concept has been adapted to the PROBA2
  mini-satellite requirements (compactness, low power electronics and
  a-thermal opto-mechanical system). It also takes advantage of the
  platform pointing agility, on-board processor, Packetwire interface
  and autonomous operations. The key component of SWAP is a radiation
  resistant CMOS-APS detector combined with onboard compression and
  data prioritization. SWAP has been developed and qualified at the
  Centre Spatial de LiÃ¨ge (CSL) and calibrated at the PTBBessy
  facility. After launch, SWAP has provided its first images on 14th
  November 2009 and started its nominal, scientific phase in February
  2010, after 3 months of platform and payload commissioning. This
  paper summarizes the latest SWAP developments and qualifications,
  and presents the first light results.

Title: SWAP onboard PROBA2: An Innovative EUV Imager Designed for
    Space Weather
Authors: de Groof, A.; Berghmans, D.; Defise, J. M.; Nicula, B.;
   Schuehle, U.
Bibcode: 2008ESPM...122.116D
Altcode:
  PROBA2 (PRoject for OnBoard Autonomy) is an ESA micro-satellite
  that is being prepared for launch in 2009. Its primary goal is the
  demonstration of new technologies in the space environment. Furthermore,
  the satellite carries an ambitious suite of both in-situ and
  remote sensing instruments for monitoring space weather, despite
  the modest onboard resources. Both the spacecraft and the remote
  sensing instruments are mainly developed within Belgium. <P />One of
  the main instruments, SWAP (Sun Watcher with APS detectors and image
  Processing), is a compact EUV imager. It carries the first APS detector
  with an EUV sensitive scintillator coating to be flown in orbit. In
  addition to the new detector, the PROBA2/SWAP design is innovative
  in the sense that the instrument will make heavy use of on-board data
  processing and autonomous operations. These will range from automatic
  off-pointing and tracking of appropriate solar events, to pre-downlink
  data prioritisation, and feature and event recognition procedures. <P
  />We discuss the first results of the SWAP pre-flight calibration and
  the strengths and weaknesses of the instrument [2]. With a narrow
  spectral bandpass centred around 17.4nm, a FOV of 54 arcmin and an
  image cadence of 1 min, its design is ideal for monitoring most CME
  associated phenomena on the solar disk and close to the limb. <P />[1]
  Defise J., Halain J., Berghmans D., et al. 2007, In: Proc. SPIE, 6689,
  66890S <P />[2] De Groof A., Berghmans D., Nicula B., et al. 2008,
  Solar Phys. 249, 147-163

Title: CMOS-APS Detectors for Solar Physics: Lessons Learned during
    the SWAP Preflight Calibration
Authors: De Groof, A.; Berghmans, D.; Nicula, B.; Halain, J. -P.;
   Defise, J. -M.; Thibert, T.; Schühle, U.
Bibcode: 2008SoPh..249..147D
Altcode: 2008SoPh..tmp...62D
  CMOS-APS imaging detectors open new opportunities for remote sensing
  in solar physics beyond what classical CCDs can provide, offering
  far less power consumption, simpler electronics, better radiation
  hardness, and the possibility of avoiding a mechanical shutter. The
  SWAP telescope onboard the PROBA2 technology demonstration satellite
  of the European Space Agency will be the first actual implementation
  of a CMOS-APS detector for solar physics in orbit. One of the goals
  of the SWAP project is precisely to acquire experience with the
  CMOS-APS technology in a real-live space science context. Such a
  precursor mission is essential in the preparation of missions such as
  Solar Orbiter where the extra CMOS-APS functionalities will be hard
  requirements. The current paper concentrates on specific CMOS-APS
  issues that were identified during the SWAP preflight calibration
  measurements. We will discuss the different readout possibilities that
  the CMOS-APS detector of SWAP provides and their associated pros and
  cons. In particular we describe the "image lag" effect, which results in
  a contamination of each image with a remnant of the previous image. We
  have characterised this effect for the specific SWAP implementation
  and we conclude with a strategy on how to successfully circumvent the
  problem and actually take benefit of it for solar monitoring.

Title: SWAP: a novel EUV telescope for space weather
Authors: Defise, Jean-Marc; Halain, Jean-Philippe; Berghmans,
   David; Denis, François; Mazy, Emmanuel; Thibert, Tanguy; Lecat,
   Jean-Hervé; Rochus, Pierre; Nicula, Bogdan; De Groof, Anik; Hochedez,
   Jean-François; Schühle, Udo; Ravet, Marie-Françoise; Delmotte, Frank
Bibcode: 2007SPIE.6689E..0SD
Altcode: 2007SPIE.6689E..24D
  The SWAP telescope (Sun Watcher using Active Pixel System detector and
  Image Processing) is being developed to be part of the PROBA2 payload,
  an ESA technological mission to be launched in early 2008. SWAP
  is directly derived from the concept of the EIT telescope that we
  developed in the '90s for the SOHO mission. Several major innovations
  have been introduced in the design of the instrument in order to
  be compliant with the requirements of the PROBA2 mini-satellite:
  compactness with a new of-axis optical design, radiation resistance
  with a new CMOS-APS detector, a very low power electronics, an athermal
  opto-mechanical system, optimized onboard compression schemes combined
  with prioritization of collected data, autonomy with automatic
  triggering of observation and off-pointing procedures in case of
  Solar event occurrence, ... All these new features result from the low
  resource requirements (power, mass, telemetry) of the mini-satellite,
  but also take advantage of the specificities of a modern technological
  platform, such as quick pointing agility, new powerful on-board
  processor, Packetwire interface and autonomous operations. These
  new enhancements will greatly improve the operations of SWAP as
  a space weather sentinel from a low Earth orbit while the downlink
  capabilities are limited. This paper summarizes the conceptual design,
  the development and the qualification of the instrument, the autonomous
  operations and the expected performances for science exploitation.

Title: a Multi-Wavelength View on Coronal Rain
Authors: Müller, D. A. N.; de Groof, A.; de Pontieu, B.; Hansteen,
   V. H.
Bibcode: 2005ESASP.600E..30M
Altcode: 2005dysu.confE..30M; 2005ESPM...11...30M
  No abstract at ADS

Title: The Dynamic Sun: Challenges for Theory and Observations
Authors: Danesy, D.; Poedts, S.; de Groof, A.; Andries, J.
Bibcode: 2005ESASP.600E....D
Altcode: 2005dysu.confE....D; 2005ESPM...11.....D
  No abstract at ADS

Title: Multiwavelength Analysis of Downflows Along AN Off-Limb Loop
Authors: de Groof, A.; Müller, D. A. N.; Poedts, S.
Bibcode: 2005ESASP.600E..29D
Altcode: 2005ESPM...11...29D; 2005dysu.confE..29D
  No abstract at ADS

Title: Downflows Along AN Off-Limb Loop Seen both in 30.4NM and Hα
Authors: de Groof, A.; Müller, D. A. N.; Poedts, S.
Bibcode: 2005ESASP.596E..36D
Altcode: 2005ccmf.confE..36D
  No abstract at ADS

Title: a Multi-Wavelength View on Coronal Rain
Authors: Müller, D. A. N.; de Groof, A.; de Pontieu, B.; Hansteen,
   V. H.
Bibcode: 2005ESASP.596E..37M
Altcode: 2005ccmf.confE..37M
  No abstract at ADS

Title: Detailed comparison of downflows seen both in EIT 30.4 nm
    and Big Bear Hα movies
Authors: de Groof, A.; Bastiaensen, C.; Müller, D. A. N.; Berghmans,
   D.; Poedts, S.
Bibcode: 2005A&A...443..319D
Altcode:
  An EIT shutterless campaign was conducted on 11 July 2001 and provided
  120 high-cadence (68 s) 30.4 nm images of the north-eastern quarter
  of the Sun. Systematic intensity variations are seen which appear
  to propagate along an off-disk loop-like structure. In this paper we
  study the nature of these intensity variations by confronting the EIT
  observations studied in De Groof et al. (2004, A&amp;A, 415, 1141)
  with simultaneous Hα images from Big Bear Solar Observatory. With
  the goal to carefully co-register the two image sets, we introduce a
  technique designed to compare data of two different instruments. The
  image series are first co-aligned and later overplotted in order to
  visualize and compare the behaviour of the propagating disturbances
  in both data sets. Since the same intensity variations are seen in
  the EIT 30.4 nm and in the Hα images, we confirm the interpretation
  of De Groof et al. (2004, A&amp;A, 415, 1141) that we are observing
  downflows of relatively cool plasma. The origin of the downflows is
  explained by numerical simulations of "catastrophic cooling" in a
  coronal loop which is heated predominantly at its footpoints.

Title: High-speed coronal rain
Authors: Müller, D. A. N.; De Groof, A.; Hansteen, V. H.; Peter, H.
Bibcode: 2005A&A...436.1067M
Altcode:
  At high spatial and temporal resolution, coronal loops are observed to
  have a highly dynamic nature. Recent observations with SOHO and TRACE
  frequently show localized brightenings "raining" down towards the solar
  surface. What is the origin of these features? Here we present for
  the first time a comparison of observed intensity enhancements from an
  EIT shutterless campaign with non-equilibrium ionization simulations
  of coronal loops in order to reveal the physical processes governing
  fast flows and localized brightenings. We show that catastrophic cooling
  around the loop apex as a consequence of footpoint-concentrated heating
  offers a simple explanation for these observations. An advantage of
  this model is that no external driving mechanism is necessary as the
  dynamics result entirely from the non-linear character of the problem.

Title: Coronal MHD Waves and Theoretical Constraints of Wave Heating
Authors: Poedts, S.; de Groof, A.
Bibcode: 2004ESASP.575...62P
Altcode: 2004soho...15...62P
  No abstract at ADS

Title: Thermal Instability as the Origin of High Speed Coronal Rain
Authors: Müller, D. A. N.; de Groof, A.; Hansteen, V. H.; Peter, H.
Bibcode: 2004ESASP.575..291M
Altcode: 2004soho...15..291M
  No abstract at ADS

Title: Intensity variations in EIT shutterless mode: Waves or flows?
Authors: De Groof, A.; Berghmans, D.; van Driel-Gesztelyi, L.;
   Poedts, S.
Bibcode: 2004A&A...415.1141D
Altcode:
  On 11 July 2001 an EIT shutterless campaign was conducted which provided
  120 high-cadence (68 s) 304 Å images of the north eastern quarter of
  the Sun. The most interesting feature seen in the data is an off-limb
  half loop structure along which systematic intensity variations are
  seen which appear to propagate from the top of the loop towards its
  footpoint. We investigate the underlying cause of these propagating
  disturbances, i.e. whether they are caused by waves or by plasma
  flows. First we identify 7 blobs with the highest intensities and
  follow them along the loop. By means of a location-time plot, bulk
  velocities can be measured at several locations along the loop. The
  velocity curve found this way is then compared with characteristic
  wave speeds and with the free-fall speed in order to deduce the nature
  of the intensity variations. Additional information on density and
  temperature is derived by measuring the relative intensity enhancements
  and comparing the EIT 304 Å sequence with Big Bear data and 171 Å
  data (TRACE/EIT). The combination of all these constraints gives us an
  insight on the nature and origin of these intensity variations. The
  idea of slow magneto-acoustic waves is rejected, and we find several
  arguments supporting that these intensity variations are due to
  flowing/falling plasma blobs.

Title: Active Region Oscillations as Observed by CDS, EIT and TRACE
Authors: Banerjee, D.; O'Shea, E.; de Groof, A.; Poedts, S.
Bibcode: 2004ESASP.547...39B
Altcode: 2004soho...13...39B
  No abstract at ADS

Title: Thermal non-equilibrium in coronal loops: A road to complex
    evolution
Authors: Müller, Daniel; de Groof, A.; Hansteen, V. H.; Peter, H.
Bibcode: 2004IAUS..223..289M
Altcode: 2005IAUS..223..289M
  At high spatial and temporal resolution, coronal loops are observed to
  have a highly dynamic nature. Recent observations with SOHO and TRACE
  frequently show localized brightening "raining" down towards the solar
  surface. What is the origin of these features? Here we present for
  the first time a comparison of observed intensity enhancements from an
  EIT shutterless campaign with non-equilibrium ionization simulations
  of coronal loops in order to reveal the physical processes governing
  fast flows and localized brightening. We show that catastrophic cooling
  around the loop apex as a consequence of footpoint-concentrated heating
  offers a simple explanation for these observations. An advantage of
  this model is that no external driving mechanism is necessary as the
  dynamics result entirely from the non-linear character of the system.

Title: Intensity Variations in EIT Shutterless Mode: Waves or Flows?
Authors: de Groof, A.; Berghmans, D.; van Driel-Gesztelyi, L.;
   Poedts, S.
Bibcode: 2004ESASP.547..245D
Altcode: 2004soho...13..245D
  On 11 July 2001 an EIT shutterless campaign was conducted which provided
  120 high-cadence (68s) 304 Å images of the north eastern quarter of the
  Sun. The most interesting feature seen in the data is an off-limb half
  loop structure along which systematic intensity variations appear to
  propagate from the top of the loop towards its footpoint. We investigate
  the underlying cause of these propagating disturbances, i.e. whether
  they are caused by waves or by plasma flows. First we identify 7 blobs
  with the highest intensities and follow them along the loop. By means
  of a location-time plot, bulk velocities can be measured at several
  locations along the loop. The velocity curve found this way is then
  compared with characteristic wave speeds and with the free-fall speed
  in order to deduce the nature of the intensity variations. Additional
  information is derived by measuring the relative intensity enhancements
  and comparing the EIT 304 Å sequence with Big Bear and 171 Å data. The
  idea of slow magneto-acoustic waves is rejected, and we find several
  arguments supporting that these intensity variations are due to
  flowing/falling plasma blobs.

Title: Waves and oscillations in magnetic fields
Authors: Goossens, Marcel; de Groof, Anik; Andries, Jesse
Bibcode: 2002ESASP.505..137G
Altcode: 2002solm.conf..137G; 2002IAUCo.188..137G
  This paper gives an overview of the theory of MHD waves in magnetic
  plasma configurations in the solar atmosphere. The emphasis is on basic
  properties that are independent of specific equilibrium models but
  are rather related to the intrinsic structuring and non-uniformity
  of the plasma. The discussion is confined to MHD waves in uniform
  and 1-d cylindrical equilibrium models of magnetic flux tubes with
  a straight magnetic field. These models contain sufficient physics
  for understanding basic properties of MHD waves and still allow for
  a relatively straightforward and transparent mathematical analysis.

Title: Fast and Alfvén waves driven by azimuthal footpoint motions
Authors: de Groof, Anik; Goossens, Marcel
Bibcode: 2002ESASP.505..389D
Altcode: 2002solm.conf..389D; 2002IAUCo.188..389D
  The excitation of Alfvén and fast magnetosonic waves in footpoint
  driven coronal loops is studied in the framework of resonant
  absorption. Previous studies revealed that in case of radial footpoint
  motions, quasi-modes are essential for effective wave dissipation
  in the loops. We now investigate the role they play in azimuthally
  driven loops. For a periodic driver, the efficiency of resonant
  absorption strongly depends on the driving frequency ω<SUB>d</SUB>:
  only for quasi-mode frequencies coupling has a positive effect on the
  growth of the (single) Alfvén resonance. The problem of single-shell
  heating can be solved by considering a more realistic, random driver:
  a variety of resonant Alfvén waves are excited and multiple resonant
  peaks appear, with length scales which are short enough for effective
  dissipation. When more realistic loop lengths are considered, the
  resonant surfaces are even more numerous resulting in globally heated
  loops.

Title: Fast and Alfvén waves driven by azimuthal footpoint
    motions. I. Periodic driver
Authors: De Groof, A.; Paes, K.; Goossens, M.
Bibcode: 2002A&A...386..681D
Altcode:
  The excitation of Alfvén and fast magneto-acoustic waves in coronal
  loops driven by footpoint motions is studied in linear, ideal MHD. The
  analysis is restricted to azimuthally polarized footpoint motions
  so that only Alfvén waves are directly excited which couple to
  fast magneto-acoustic waves at later times. In the present study a
  periodic driver is applied at one end of the loop. The effects of a
  more realistic random driver are studied in the companion paper De
  Groof &amp; Goossens (2002) (hereafter referred to as Paper II). The
  first part of the paper is devoted to the study of resonant absorption
  and phase-mixing in the absence of coupling (azimuthal wavenumber
  k<SUB>y</SUB>=0). Since the density varies across the loop, resonances
  occur at the magnetic surfaces where the driving frequency equals the
  local Alfvén frequency. In a second part where Alfvén waves with
  k<SUB>y</SUB> !=q 0 coupling to fast waves are taken into account, we
  find that the behaviour of the MHD waves is strongly dependent on the
  driving frequency omega<SUB>d</SUB> . Especially driving frequencies
  equal to a quasi-mode frequency seem to make the difference. The fast
  waves excited in these cases are global oscillations of the system
  and form quasi-modes as they are damped through the resonant coupling
  with Alfvén modes. Since these resonances occur at the same location
  where the original Alfvén wave peaks, the resonant peak is further
  amplified. While in most cases coupling has a negative effect on the
  growth of the directly excited Alfvén waves, driving with a quasi-mode
  frequency leads to a faster growth of the resonant peaks and a more
  efficient decrease in length scales than in the uncoupled case.

Title: Fast and Alfvén waves driven by azimuthal footpoint
    motions. II. Random driver
Authors: De Groof, A.; Goossens, M.
Bibcode: 2002A&A...386..691D
Altcode:
  The excitation of Alfvén and fast magneto-acoustic waves in coronal
  loops driven by footpoint motions is studied in linear, ideal MHD. The
  analysis is restricted to azimuthally polarized footpoint motions
  so that only Alfvén waves are directly excited to couple to fast
  magneto-acoustic waves at later times. In the companion paper De
  Groof et al. (\cite{Groof02a}) (hereafter referred to as Paper I),
  the behaviour of the MHD waves is studied in case of a monochromatic
  driver. In the present study, the effects of a more realistic random
  driver are investigated.\ First, we consider loops of equal length and
  width in order to limit the number of quasi-modes in the frequency
  range of the driver so that the influence of quasi-modes in the
  system can easily be detected. In contrast to the single resonant
  surface which was found in case of a periodic driver (see Paper I),
  a random pulse train excites a variety of resonant Alfvén waves and
  consequently the small length scales built up are spread over the
  whole width of the loop. The specific effects of the quasi-modes are
  not so easily recognized as for radial footpoint motions (De Groof
  &amp; Goossens \cite{Groof00a}) since the resonances corresponding to
  directly and indirectly excited Alfvén waves are mixed together. In
  the second part of the paper, longer loops are considered. Since more
  quasi-modes are involved, the resonant surfaces are more numerous and
  widely spread throughout the whole loop volume. On the other hand,
  it takes more time for the MHD waves to cross the loop and to form
  standing waves. Nevertheless this negative effect does not have too much
  impact since the simulations show that after a small time interval,
  resonant surfaces are created all over the loop, with length scales
  which are short enough for effective dissipation.

Title: Resonant absorption in randomly driven coronal loops
Authors: de Groof, Anik; Goossens, Marcel
Bibcode: 2000AIPC..537..208D
Altcode: 2000wdss.conf..208D
  De Groof et al. '98 [1] and '00 [2] studied the time evolution of fast
  magnetosonic and Alfvén waves in a coronal loop driven by radially
  polarized footpoint motions in linear ideal MHD. Footpoint driving
  seems to be an efficient way of generating resonant absorption since the
  input energy is mainly stored in body modes which keep the energy in the
  loop. The most important feature in this study is the stochastic driving
  of the loop. While in earlier models with a periodic driver or a single
  pulse, the loop is only heated at one single layer, we now find multiple
  resonance layers which results in a more globally heated loop. Moreover,
  these resonances (created on a realistic time scale) have length scales
  which are small enough to explain energy dissipation. An important
  aspect to take into account is the mass transfer between corona and
  chromosphere since the density becomes time dependent and consequently,
  the resonant surfaces shift throughout the loop [3]. Combined with
  the multiple resonances we found in the previous study, this result
  can lead to the globally heated coronal loops we observe. .

Title: Randomly driven fast waves in coronal loops. II. with coupling
    to Alfvén waves
Authors: De Groof, A.; Goossens, M.
Bibcode: 2000A&A...356..724D
Altcode:
  We study the time evolution of fast magnetosonic and Alfvén waves in a
  coronal loop driven by random footpoint motions. The footpoint motions
  are assumed to be polarized normal to the magnetic flux surfaces in
  linear ideal MHD. De Groof et al. (1998) (Paper I) showed that the
  input energy is mainly stored in the body modes when the fast waves
  are decoupled from the Alfvén waves. Hence driving at the loop's feet
  forms a good basis for resonant absorption as heating mechanism. In
  order to determine the efficiency of resonant absorption, we therefore
  study the energy transfer from the body modes to the resonant Alfvén
  waves in the case of coupling. We find that the growth of Alfvén mode
  energy depends on several parameters. Subsequently we check whether
  the necessary small lengthscales are created on a realistic time scale
  for the coronal loop. We find that Alfvén resonances are built up
  at the magnetic surfaces, where local Alfvén frequencies equal the
  quasi-modes frequencies, on time scales comparable to the lifetime
  of the loop. Finally we conclude that a random footpoint driving can
  produce enough resonances to give rise to a globally heated coronal
  loop.

Title: Randomly Driven Fast Waves in Coronal Loops
Authors: de Groof, A.; Goossens, M.
Bibcode: 1999ESASP.448..251D
Altcode: 1999ESPM....9..251D; 1999mfsp.conf..251D
  No abstract at ADS

Title: Random driven fast waves in coronal loops. I. Without coupling
    to Alfven waves
Authors: de Groof, A.; Tirry, W. J.; Goossens, M.
Bibcode: 1998A&A...335..329D
Altcode:
  In this paper we study the time evolution of fast MHD waves in a coronal
  loop driven by footpoint motions in linear ideal MHD. We restrict the
  analysis to footpoint motions polarized normal to the magnetic flux
  surfaces such that the fast waves are driven directly. By supposing
  the azimuthal wave number k_y to be zero, the fast waves are decoupled
  from the Alfven waves. As a first step to real stochastic driving,
  we consider the loop to be driven by a train of identical pulses
  with random time intervals in between. The solution is written as a
  superposition of eigenmodes whose excitation is determined by the
  time dependence of the footpoint motion through a convolution and
  by the spatial dependence of the footpoint motion through a scalar
  product. An important result from the simulations is that the amount
  of kinetic energy associated with the body modes is much larger than
  the amount corresponding to the leaky modes. This means that most of
  the input energy is stored within the loop. For k_y!=q 0, body modes
  can resonantly couple to Alfven waves at certain magnetic surfaces
  and hence the energy of the body modes can then be dissipated around
  the resonant magnetic surfaces. Using a gamma distribution for the
  time intervals between the successive pulses, we analytically derive
  a relation between the mean value of the kinetic energy contribution
  of each eigenmode, the eigenfrequency, the number of pulses and the
  width of the pulses. The larger the variance of the distribution, the
  less the power spectrum reveals fine structure, peaks around certain
  preferred frequencies. The analytical results confirm the output from
  the numerical simulations.

