Author name code: morton
ADS astronomy entries on 2022-09-14
author:"Morton, Richard J." 
------------------------------------------------------------------------  

Title: Alfvénic waves in the inhomogeneous solar atmosphere
Authors: Morton, R. J.; Sharma, R.; Tajfirouzhe, E.; Miriyala, H.
Bibcode: 2022arXiv220805222M
Altcode:
  The solar atmosphere is known to be replete with magneto-hydrodynamic
  wave modes, and there has been significant investment in understanding
  how these waves propagate through the Sun's atmopshere and deposit
  their energy into the plasma. The waves' journey is made interesting
  by the vertical variation in plasma quantities that define the solar
  atmosphere. In addition to this large-scale inhomogeneity, a wealth
  of fine-scale structure through the chromosphere and corona has been
  brought to light by high-resolution observations over the last couple
  of decades. This fine-scale sturcture represents inhomogeneity that
  is thought to be perpendicular to the local magnetic fields. The
  implications of this form of inhomogeneity on wave propagation is
  still being uncovered, but is known to fundamentally change the
  nature of MHD wave modes. It also enables interesting physics to
  arise including resonances, turbulence and instabilities. Here we
  review some of the key insights into how the inhomogeneity influences
  Alfvénic wave propagation through the Sun's atmosphere, discussing
  both inhomogeneities parallel and perpendicular to the magnetic field.

Title: Magnetoseismology for the solar corona: from  10 Gauss to
    coronal magnetograms
Authors: Yang, Zihao; Gibson, Sarah; He, Jiansen; Del Zanna, Giulio;
   Tomczyk, Steven; Morton, Richard; McIntosh, Scott; Wang, Linghua;
   Karak, Bidya Binay; Samanta, Tanmoy; Tian, Hui; Chen, Yajie; Bethge,
   Christian; Bai, Xianyong
Bibcode: 2022cosp...44.2490Y
Altcode:
  Magnetoseismology, a technique of magnetic field diagnostics based
  on observations of magnetohydrodynamic (MHD) waves, has been widely
  used to estimate the field strengths of oscillating structures in
  the solar corona. However, previously magnetoseismology was mostly
  applied to occasionally occurring oscillation events, providing
  an estimate of only the average field strength or one-dimensional
  distribution of field strength along an oscillating structure. This
  restriction could be eliminated if we apply magnetoseismology to the
  pervasive propagating transverse MHD waves discovered with the Coronal
  Multi-channel Polarimeter (CoMP). Using several CoMP observations of
  the Fe XIII 1074.7 nm and 1079.8 nm spectral lines, we obtained maps of
  the plasma density and wave phase speed in the corona, which allow us
  to map both the strength and direction of the coronal magnetic field
  in the plane of sky. We also examined distributions of the electron
  density and magnetic field strength, and compared their variations
  with height in the quiet Sun and active regions. Such measurements
  could provide critical information to advance our understanding of the
  Sun's magnetism and the magnetic coupling of the whole solar atmosphere.

Title: Parallel Plasma Loops and the Energization of the Solar Corona
Authors: Peter, Hardi; Chitta, Lakshmi Pradeep; Chen, Feng; Pontin,
   David I.; Winebarger, Amy R.; Golub, Leon; Savage, Sabrina L.;
   Rachmeler, Laurel A.; Kobayashi, Ken; Brooks, David H.; Cirtain,
   Jonathan W.; De Pontieu, Bart; McKenzie, David E.; Morton, Richard J.;
   Testa, Paola; Tiwari, Sanjiv K.; Walsh, Robert W.; Warren, Harry P.
Bibcode: 2022ApJ...933..153P
Altcode: 2022arXiv220515919P
  The outer atmosphere of the Sun is composed of plasma heated to
  temperatures well in excess of the visible surface. We investigate
  short cool and warm (&lt;1 MK) loops seen in the core of an active
  region to address the role of field-line braiding in energizing these
  structures. We report observations from the High-resolution Coronal
  imager (Hi-C) that have been acquired in a coordinated campaign with
  the Interface Region Imaging Spectrograph (IRIS). In the core of the
  active region, the 172 Å band of Hi-C and the 1400 Å channel of IRIS
  show plasma loops at different temperatures that run in parallel. There
  is a small but detectable spatial offset of less than 1″ between
  the loops seen in the two bands. Most importantly, we do not see
  observational signatures that these loops might be twisted around each
  other. Considering the scenario of magnetic braiding, our observations
  of parallel loops imply that the stresses put into the magnetic field
  have to relax while the braiding is applied: the magnetic field never
  reaches a highly braided state on these length scales comparable to
  the separation of the loops. This supports recent numerical 3D models
  of loop braiding in which the effective dissipation is sufficiently
  large that it keeps the magnetic field from getting highly twisted
  within a loop.

Title: Magnetoseismology for the solar corona: from  10 Gauss to
    coronal magnetograms
Authors: Yang, Zihao; Bethge, Christian; Tian, Hui; Tomczyk, Steven;
   Morton, Richard; Del Zanna, Giulio; McIntosh, Scott; Karak, Bidya
   Binay; Gibson, Sarah; Samanta, Tanmoy; He, Jiansen; Chen, Yajie; Bai,
   Xianyong; Wang, Linghua
Bibcode: 2021AGUFMSH12C..07Y
Altcode:
  Magnetoseismology, a technique of magnetic field diagnostics based
  on observations of magnetohydrodynamic (MHD) waves, has been widely
  used to estimate the field strengths of oscillating structures in
  the solar corona. However, previously magnetoseismology was mostly
  applied to occasionally occurring oscillation events, providing
  an estimate of only the average field strength or one-dimensional
  distribution of field strength along an oscillating structure. This
  restriction could be eliminated if we apply magnetoseismology to the
  pervasive propagating transverse MHD waves discovered with the Coronal
  Multi-channel Polarimeter (CoMP). Using several CoMP observations of
  the Fe XIII 1074.7 nm and 1079.8 nm spectral lines, we obtained maps of
  the plasma density and wave phase speed in the corona, which allow us
  to map both the strength and direction of the coronal magnetic field
  in the plane of sky. We also examined distributions of the electron
  density and magnetic field strength, and compared their variations
  with height in the quiet Sun and active regions. Such measurements
  could provide critical information to advance our understanding of the
  Sun's magnetism and the magnetic coupling of the whole solar atmosphere.

Title: Is phase mixing important in the quiet Sun?
Authors: Morton, Richard; McLaughlin, James; Tiwari, Ajay; Van
   Doorsselaere, Tom
Bibcode: 2021AGUFMSH12B..09M
Altcode:
  The focus of many investigations on coronal wave heating has been to
  scrutinise the role of transverse (i.e. kink) modes; examining their
  damping by resonant absorption and the transfer of energy to Alfvén
  modes. Subsequently, the Alfvén modes are then subject to phase
  mixing and this leads to plasma heating. More recently, a non-linear
  mechanism for energy transfer has also been proposed, the so called
  uni-turbulence. Due to the ease with which they have been observed,
  the rapidly damped standing kink modes in active regions have spawned
  numerous studies investigating the role of resonant absorption in
  the observed damping. However, their counterparts in the quiet Sun,
  the propagating kink waves, have received little attention. Here I
  will discuss the results from a large-scale study of kink wave damping
  in the quiet Sun. We find convincing evidence that the damping of the
  kink waves is significantly weaker than in active regions and suggests
  that resonant absorption/phase mixing/uni-turbulence are not important
  mechanisms for wave-based heating of the quiescent Sun. I will also
  discuss the physical reason we suspect is behind this result and what
  it tells us about the fine-scale structure of the quiescent corona.

Title: Tracking the Alfven Waves in Closed Coronal Structure
Authors: Tajfirouze, Edris; Morton, Richard; Asgari-Targhi, Mahboubeh
Bibcode: 2021AGUFMSH25A2080T
Altcode:
  Alfvén waves are potential candidates to explain the heating of the
  solar corona, since they can propagate long distances from the source
  where they originate up to the corona without significant damping. They
  are believed to be driven by the turbulent convective motions in
  the photosphere, and predominantly propagate upwards into the corona
  along network magnetic fields. However, the mechanism by which they
  convert their energy into plasma heating is still under debate. One
  scenario is that counter propagating Alfvén waves can interact
  nonlinearly and create turbulence. Energy cascades from the larger
  scales to small scale where it can be dissipated, e.g., by viscosity
  and resistivity. To date, observations of Alfvénic waves in the
  corona have been limited. The Coronal Multi-Channel Polarimeter (CoMP)
  provides remote observations of the off-limb corona, and has revealed
  Alfvénic velocity fluctuations are ubiquitous. The observations are
  currently limited to examining parallel wavenumbers, with the velocity
  power spectral density displaying power law behaviour that possess a
  range of spectral indices across the corona. The slope of the power
  spectra is related to the parallel correlation time of the waves in
  the corona. Given that the photospheric motions should have the same
  correlation time across the Sun (maybe with the exception of active
  regions), this may indicate that the different coronal spectral indices
  are the results of different magnetic/plasma conditions influencing
  the evolution of the waves through the lower solar atmosphere. Here,
  we present results on how Alfvén waves are influenced by different
  magnetic field conditions using a Reduced Magneto Hydrodynamic
  (RMHD) model which incorporates the wave turbulence and describes the
  propagation and dissipation of Alfvén waves along a single flux tube.

Title: Weak Damping of Propagating MHD Kink Waves in the Quiescent
    Corona
Authors: Morton, Richard J.; Tiwari, Ajay K.; Van Doorsselaere, Tom;
   McLaughlin, James A.
Bibcode: 2021ApJ...923..225M
Altcode: 2021arXiv210511924M
  Propagating transverse waves are thought to be a key transporter of
  Poynting flux throughout the Sun's atmosphere. Recent studies have shown
  that these transverse motions, interpreted as the magnetohydrodynamic
  kink mode, are prevalent throughout the corona. The associated energy
  estimates suggest the waves carry enough energy to meet the demands
  of coronal radiative losses in the quiescent Sun. However, it is still
  unclear how the waves deposit their energy into the coronal plasma. We
  present the results from a large-scale study of propagating kink waves
  in the quiescent corona using data from the Coronal Multi-channel
  Polarimeter (CoMP). The analysis reveals that the kink waves appear
  to be weakly damped, which would imply low rates of energy transfer
  from the large-scale transverse motions to smaller scales via either
  uniturbulence or resonant absorption. This raises questions about how
  the observed kink modes would deposit their energy into the coronal
  plasma. Moreover, these observations, combined with the results of Monte
  Carlo simulations, lead us to infer that the solar corona displays a
  spectrum of density ratios, with a smaller density ratio (relative to
  the ambient corona) in quiescent coronal loops and a higher density
  ratio in active-region coronal loops.

Title: A Statistical Study of Propagating MHD Kink Waves in the
    Quiescent Corona
Authors: Tiwari, Ajay K.; Morton, Richard J.; McLaughlin, James A.
Bibcode: 2021ApJ...919...74T
Altcode: 2021arXiv210512451T
  The Coronal Multi-channel Polarimeter (CoMP) has opened up exciting
  opportunities to probe transverse MHD waves in the Sun's corona. The
  archive of CoMP data is utilized to generate a catalog of quiescent
  coronal loops that can be used for studying propagating kink waves. The
  catalog contains 120 loops observed between 2012 and 2014. This catalog
  is further used to undertake a statistical study of propagating kink
  waves in the quiet regions of the solar corona, investigating phase
  speeds, loop lengths, footpoint power ratio (a measure of wave power
  entering the corona through each footpoint of a loop) and equilibrium
  parameter (which provides a measure of the change in wave amplitude)
  values. The statistical study enables us to establish the presence of a
  relationship between the rate of damping and the length of the coronal
  loop, with longer coronal loops displaying weaker wave damping. We
  suggest the reason for this behavior is related to a decreasing average
  density contrast between the loop and ambient plasma as loop length
  increases. The catalog presented here will provide the community with
  the foundation for the further study of propagating kink waves in the
  quiet solar corona.

Title: Mapping the global magnetic field in the solar corona through
    magnetoseismology
Authors: Yang, Zihao; Bethge, Christian; Tian, Hui; Tomczyk, Steven;
   Morton, Richard; Del Zanna, Giulio; McIntosh, Scott; Karak, Bidya
   Binay; Gibson, Sarah; Samanta, Tanmoy; He, Jiansen; Chen, Yajie;
   Wang, Linghua; Bai, Xianyong
Bibcode: 2021EGUGA..23..642Y
Altcode:
  Magnetoseismology, a technique of magnetic field diagnostics based
  on observations of magnetohydrodynamic (MHD) waves, has been widely
  used to estimate the field strengths of oscillating structures in
  the solar corona. However, previously magnetoseismology was mostly
  applied to occasionally occurring oscillation events, providing
  an estimate of only the average field strength or one-dimensional
  distribution of field strength along an oscillating structure. This
  restriction could be eliminated if we apply magnetoseismology to the
  pervasive propagating transverse MHD waves discovered with the Coronal
  Multi-channel Polarimeter (CoMP). Using several CoMP observations of
  the Fe XIII 1074.7 nm and 1079.8 nm spectral lines, we obtained maps of
  the plasma density and wave phase speed in the corona, which allow us
  to map both the strength and direction of the coronal magnetic field
  in the plane of sky. We also examined distributions of the electron
  density and magnetic field strength, and compared their variations
  with height in the quiet Sun and active regions. Such measurements
  could provide critical information to advance our understanding of the
  Sun's magnetism and the magnetic coupling of the whole solar atmosphere.

Title: Critical Science Plan for the Daniel K. Inouye Solar Telescope
    (DKIST)
Authors: Rast, Mark P.; Bello González, Nazaret; Bellot Rubio,
   Luis; Cao, Wenda; Cauzzi, Gianna; Deluca, Edward; de Pontieu, Bart;
   Fletcher, Lyndsay; Gibson, Sarah E.; Judge, Philip G.; Katsukawa,
   Yukio; Kazachenko, Maria D.; Khomenko, Elena; Landi, Enrico; Martínez
   Pillet, Valentín; Petrie, Gordon J. D.; Qiu, Jiong; Rachmeler,
   Laurel A.; Rempel, Matthias; Schmidt, Wolfgang; Scullion, Eamon; Sun,
   Xudong; Welsch, Brian T.; Andretta, Vincenzo; Antolin, Patrick; Ayres,
   Thomas R.; Balasubramaniam, K. S.; Ballai, Istvan; Berger, Thomas E.;
   Bradshaw, Stephen J.; Campbell, Ryan J.; Carlsson, Mats; Casini,
   Roberto; Centeno, Rebecca; Cranmer, Steven R.; Criscuoli, Serena;
   Deforest, Craig; Deng, Yuanyong; Erdélyi, Robertus; Fedun, Viktor;
   Fischer, Catherine E.; González Manrique, Sergio J.; Hahn, Michael;
   Harra, Louise; Henriques, Vasco M. J.; Hurlburt, Neal E.; Jaeggli,
   Sarah; Jafarzadeh, Shahin; Jain, Rekha; Jefferies, Stuart M.; Keys,
   Peter H.; Kowalski, Adam F.; Kuckein, Christoph; Kuhn, Jeffrey R.;
   Kuridze, David; Liu, Jiajia; Liu, Wei; Longcope, Dana; Mathioudakis,
   Mihalis; McAteer, R. T. James; McIntosh, Scott W.; McKenzie, David
   E.; Miralles, Mari Paz; Morton, Richard J.; Muglach, Karin; Nelson,
   Chris J.; Panesar, Navdeep K.; Parenti, Susanna; Parnell, Clare E.;
   Poduval, Bala; Reardon, Kevin P.; Reep, Jeffrey W.; Schad, Thomas A.;
   Schmit, Donald; Sharma, Rahul; Socas-Navarro, Hector; Srivastava,
   Abhishek K.; Sterling, Alphonse C.; Suematsu, Yoshinori; Tarr, Lucas
   A.; Tiwari, Sanjiv; Tritschler, Alexandra; Verth, Gary; Vourlidas,
   Angelos; Wang, Haimin; Wang, Yi-Ming; NSO and DKIST Project; DKIST
   Instrument Scientists; DKIST Science Working Group; DKIST Critical
   Science Plan Community
Bibcode: 2021SoPh..296...70R
Altcode: 2020arXiv200808203R
  The National Science Foundation's Daniel K. Inouye Solar Telescope
  (DKIST) will revolutionize our ability to measure, understand,
  and model the basic physical processes that control the structure
  and dynamics of the Sun and its atmosphere. The first-light DKIST
  images, released publicly on 29 January 2020, only hint at the
  extraordinary capabilities that will accompany full commissioning of
  the five facility instruments. With this Critical Science Plan (CSP)
  we attempt to anticipate some of what those capabilities will enable,
  providing a snapshot of some of the scientific pursuits that the DKIST
  hopes to engage as start-of-operations nears. The work builds on the
  combined contributions of the DKIST Science Working Group (SWG) and
  CSP Community members, who generously shared their experiences, plans,
  knowledge, and dreams. Discussion is primarily focused on those issues
  to which DKIST will uniquely contribute.

Title: An overall view of temperature oscillations in the solar
    chromosphere with ALMA
Authors: Jafarzadeh, S.; Wedemeyer, S.; Fleck, B.; Stangalini, M.;
   Jess, D. B.; Morton, R. J.; Szydlarski, M.; Henriques, V. M. J.; Zhu,
   X.; Wiegelmann, T.; Guevara Gómez, J. C.; Grant, S. D. T.; Chen,
   B.; Reardon, K.; White, S. M.
Bibcode: 2021RSPTA.37900174J
Altcode: 2021RSTPA.379..174J; 2020arXiv201001918J
  By direct measurements of the gas temperature, the Atacama Large
  Millimeter/submillimeter Array (ALMA) has yielded a new diagnostic
  tool to study the solar chromosphere. Here, we present an overview
  of the brightness-temperature fluctuations from several high-quality
  and high-temporal-resolution (i.e. 1 and 2 s cadence) time series
  of images obtained during the first 2 years of solar observations
  with ALMA, in Band 3 and Band 6, centred at around 3 mm (100 GHz)
  and 1.25 mm (239 GHz), respectively. The various datasets represent
  solar regions with different levels of magnetic flux. We perform
  fast Fourier and Lomb-Scargle transforms to measure both the spatial
  structuring of dominant frequencies and the average global frequency
  distributions of the oscillations (i.e. averaged over the entire field
  of view). We find that the observed frequencies significantly vary from
  one dataset to another, which is discussed in terms of the solar regions
  captured by the observations (i.e. linked to their underlying magnetic
  topology). While the presence of enhanced power within the frequency
  range 3-5 mHz is found for the most magnetically quiescent datasets,
  lower frequencies dominate when there is significant influence from
  strong underlying magnetic field concentrations (present inside and/or
  in the immediate vicinity of the observed field of view). We discuss
  here a number of reasons which could possibly contribute to the power
  suppression at around 5.5 mHz in the ALMA observations. However,
  it remains unclear how other chromospheric diagnostics (with an
  exception of Hα line-core intensity) are unaffected by similar
  effects, i.e. they show very pronounced 3-min oscillations dominating
  the dynamics of the chromosphere, whereas only a very small fraction
  of all the pixels in the 10 ALMA datasets analysed here show peak power
  near 5.5 mHz. <P />This article is part of the Theo Murphy meeting issue
  `High-resolution wave dynamics in the lower solar atmosphere'.

Title: Transverse motions in sunspot super-penumbral fibrils
Authors: Morton, R. J.; Mooroogen, K.; Henriques, V. M. J.
Bibcode: 2021RSPTA.37900183M
Altcode: 2020arXiv201207394M
  Sunspots have played a key role in aiding our understanding of
  magnetohydrodynamic (MHD) wave phenomena in the Sun's atmosphere, and
  it is well known they demonstrate a number of wave phenomena associated
  with slow MHD modes. Recent studies have shown that transverse wave
  modes are present throughout the majority of the chromosphere. Using
  high-resolution Ca II 8542 Å observations from the Swedish Solar
  Telescope, we provide the first demonstration that the chromospheric
  super-penumbral fibrils, which span out from the sunspot, also show
  ubiquitous transverse motions. We interpret these motions as transverse
  waves, in particular the MHD kink mode. We compile the statistical
  properties of over 2000 transverse motions to find distributions
  for periods and amplitudes, finding they are broadly consistent with
  previous observations of chromospheric transverse waves in quiet Sun
  fibrils. The very presence of the waves in super-penumbral fibrils
  raises important questions about how they are generated, and could
  have implications for our understanding of how MHD wave energy is
  transferred through the atmosphere of a sunspot. <P />This article is
  part of the Theo Murphy meeting issue `High-resolution wave dynamics
  in the lower solar atmosphere'.

Title: Effect of coronal loop structure on wave heating through
    phase mixing
Authors: Pagano, P.; De Moortel, I.; Morton, R. J.
Bibcode: 2020A&A...643A..73P
Altcode: 2020arXiv200904366P
  Context. The mechanism(s) behind coronal heating still elude(s)
  direct observation and modelling of viable theoretical processes and
  the subsequent effect on coronal structures is one of the key tools
  available to assess possible heating mechanisms. Wave heating via the
  phase mixing of magnetohydrodynamic (MHD) transverse waves has been
  proposed as a possible way to convert magnetic energy into thermal
  energy, but MHD models increasingly suggest this is not an efficient
  enough mechanism. <BR /> Aims: We modelled heating by phase mixing
  transverse MHD waves in various configurations in order to investigate
  whether certain circumstances can enhance the heating sufficiently
  to sustain the million degree solar corona and to assess the impact
  of the propagation and phase mixing of transverse MHD waves on the
  structure of the boundary shell of coronal loops. <BR /> Methods:
  We used 3D MHD simulations of a pre-existing density enhancement in a
  magnetised medium and a boundary driver to trigger the propagation of
  transverse waves with the same power spectrum as measured by the Coronal
  Multi-Channel Polarimeter. We consider different density structures,
  boundary conditions at the non-drive footpoint, characteristics of the
  driver, and different forms of magnetic resistivity. <BR /> Results:
  We find that different initial density structures significantly
  affect the evolution of the boundary shell and that some driver
  configurations can enhance the heating generated from the dissipation
  of the MHD waves. In particular, drivers coherent on a larger spatial
  scale and higher dissipation coefficients can generate significant
  heating, although it is still insufficient to balance the radiative
  losses in this setup. <BR /> Conclusions: We conclude that while
  phase mixing of transverse MHD waves is unlikely to sustain the
  thermal structure of the corona, there are configurations that allow
  for an enhanced efficiency of this mechanism. We provide possible
  signatures to identify the presence of such configurations, such as
  the location of where the heating is deposited along the coronal
  loop. <P />Movies associated to Figs. 4 and 8 are available at <A
  href="https://www.aanda.org/10.1051/0004-6361/202039209/olm">https://www.aanda.org</A>

Title: Mapping the magnetic field in the solar corona through
    magnetoseismology
Authors: Yang, ZiHao; Tian, Hui; Tomczyk, Steven; Morton, Richard;
   Bai, XianYong; Samanta, Tanmoy; Chen, YaJie
Bibcode: 2020ScChE..63.2357Y
Altcode: 2020arXiv200803146Y
  Magnetoseismology, a technique of magnetic field diagnostics based
  on observations of magnetohydrodynamic (MHD) waves, has been widely
  used to estimate the field strengths of oscillating structures in
  the solar corona. However, previously magnetoseismology was mostly
  applied to occasionally occurring oscillation events, providing
  an estimate of only the average field strength or one-dimensional
  distribution of field strength along an oscillating structure. This
  restriction could be eliminated if we apply magnetoseismology to the
  pervasive propagating transverse MHD waves discovered with the Coronal
  Multi-channel Polarimeter (CoMP). Using several CoMP observations of
  the Fe xiii 1074.7 nm and 1079.8 nm spectral lines, we obtained maps of
  the plasma density and wave phase speed in the corona, which allow us
  to map both the strength and direction of the coronal magnetic field
  in the plane of sky. We also examined distributions of the electron
  density and magnetic field strength, and compared their variations
  with height in the quiet Sun and active regions. Such measurements
  could provide critical information to advance our understanding of the
  Sun's magnetism and the magnetic coupling of the whole solar atmosphere.

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: Global maps of the magnetic field in the solar corona
Authors: Yang, Zihao; Bethge, Christian; Tian, Hui; Tomczyk, Steven;
   Morton, Richard; Del Zanna, Giulio; McIntosh, Scott W.; Karak, Bidya
   Binay; Gibson, Sarah; Samanta, Tanmoy; He, Jiansen; Chen, Yajie;
   Wang, Linghua
Bibcode: 2020Sci...369..694Y
Altcode: 2020arXiv200803136Y
  Understanding many physical processes in the solar atmosphere requires
  determination of the magnetic field in each atmospheric layer. However,
  direct measurements of the magnetic field in the Sun’s corona are
  difficult to obtain. Using observations with the Coronal Multi-channel
  Polarimeter, we have determined the spatial distribution of the
  plasma density in the corona and the phase speed of the prevailing
  transverse magnetohydrodynamic waves within the plasma. We combined
  these measurements to map the plane-of-sky component of the global
  coronal magnetic field. The derived field strengths in the corona,
  from 1.05 to 1.35 solar radii, are mostly 1 to 4 gauss. Our results
  demonstrate the capability of imaging spectroscopy in coronal magnetic
  field diagnostics.

Title: Observation and Modeling of High-temperature Solar Active
    Region Emission during the High-resolution Coronal Imager Flight of
    2018 May 29
Authors: Warren, Harry P.; Reep, Jeffrey W.; Crump, Nicholas A.;
   Ugarte-Urra, Ignacio; Brooks, David H.; Winebarger, Amy R.; Savage,
   Sabrina; De Pontieu, Bart; Peter, Hardi; Cirtain, Jonathan W.; Golub,
   Leon; Kobayashi, Ken; McKenzie, David; Morton, Richard; Rachmeler,
   Laurel; Testa, Paola; Tiwari, Sanjiv; Walsh, Robert
Bibcode: 2020ApJ...896...51W
Altcode:
  Excellent coordinated observations of NOAA active region 12712 were
  obtained during the flight of the High-resolution Coronal Imager (Hi-C)
  sounding rocket on 2018 May 29. This region displayed a typical active
  region core structure with relatively short, high-temperature loops
  crossing the polarity inversion line and bright "moss" located at the
  footpoints of these loops. The differential emission measure (DEM) in
  the active region core is very sharply peaked at about 4 MK. Further,
  there is little evidence for impulsive heating events in the moss, even
  at the high spatial resolution and cadence of Hi-C. This suggests that
  active region core heating is occurring at a high frequency and keeping
  the loops close to equilibrium. To create a time-dependent simulation of
  the active region core, we combine nonlinear force-free extrapolations
  of the measured magnetic field with a heating rate that is dependent
  on the field strength and loop length and has a Poisson waiting time
  distribution. We use the approximate solutions to the hydrodynamic
  loop equations to simulate the full ensemble of active region core
  loops for a range of heating parameters. In all cases, we find that
  high-frequency heating provides the best match to the observed DEM. For
  selected field lines, we solve the full hydrodynamic loop equations,
  including radiative transfer in the chromosphere, to simulate transition
  region and chromospheric emission. We find that for heating scenarios
  consistent with the DEM, classical signatures of energy release,
  such as transition region brightenings and chromospheric evaporation,
  are weak, suggesting that they would be difficult to detect.

Title: The Drivers of Active Region Outflows into the Slow Solar Wind
Authors: Brooks, David H.; Winebarger, Amy R.; Savage, Sabrina; Warren,
   Harry P.; De Pontieu, Bart; Peter, Hardi; Cirtain, Jonathan W.; Golub,
   Leon; Kobayashi, Ken; McIntosh, Scott W.; McKenzie, David; Morton,
   Richard; Rachmeler, Laurel; Testa, Paola; Tiwari, Sanjiv; Walsh, Robert
Bibcode: 2020ApJ...894..144B
Altcode: 2020arXiv200407461B
  Plasma outflows from the edges of active regions have been suggested as
  a possible source of the slow solar wind. Spectroscopic measurements
  show that these outflows have an enhanced elemental composition,
  which is a distinct signature of the slow wind. Current spectroscopic
  observations, however, do not have sufficient spatial resolution to
  distinguish what structures are being measured or determine the driver
  of the outflows. The High-resolution Coronal Imager (Hi-C) flew on a
  sounding rocket in 2018 May and observed areas of active region outflow
  at the highest spatial resolution ever achieved (250 km). Here we use
  the Hi-C data to disentangle the outflow composition signatures observed
  with the Hinode satellite during the flight. We show that there are
  two components to the outflow emission: a substantial contribution
  from expanded plasma that appears to have been expelled from closed
  loops in the active region core and a second contribution from dynamic
  activity in active region plage, with a composition signature that
  reflects solar photospheric abundances. The two competing drivers of the
  outflows may explain the variable composition of the slow solar wind.

Title: Using Transverse Waves to Probe the Plasma Conditions at the
    Base of the Solar Wind
Authors: Weberg, Micah J.; Morton, Richard J.; McLaughlin, James A.
Bibcode: 2020ApJ...894...79W
Altcode:
  It has long been suggested that magnetohydrodynamic (MHD) waves may
  supply a significant proportion of the energy required to heat the
  corona and accelerate the solar wind. Depending on the properties of
  the local plasma, MHD wave modes may exhibit themselves as a variety of
  incompressible, transverse waves. The local magnetic field and particle
  density influence the properties of these waves (e.g., amplitude),
  thus direct measurements of transverse waves provide a mechanism to
  indirectly probe the local plasma conditions. We present the first
  statistical approach to magnetoseismology of a localized region of the
  solar corona, analyzing transverse waves above the south polar coronal
  hole on 2011 May 23. Automated methods are utilized to examine 4 hr of
  EUV imaging data to study how the waves evolve as a function of height
  (I.e., altitude) through the low corona. Between heights of 15 and 35
  Mm, we find that the measured wave periods are approximately constant,
  and that observed displacement and velocity amplitudes increase at
  rates that are consistent with undamped waves. This enables us to
  derive a relative density profile for the coronal hole environment
  in question, without the use of spectroscopic data. Furthermore,
  our results indicate that between 5 and 15 Mm above the limb, the
  relative density is larger than that expected from 1D hydrostatic
  models, and signals a more extended transition region with a gradual
  change in density. This has implications for self-consistent models
  of wave propagation from the photosphere to the corona and beyond.

Title: Is the High-Resolution Coronal Imager Resolving Coronal
    Strands? Results from AR 12712
Authors: Williams, Thomas; Walsh, Robert W.; Winebarger, Amy R.;
   Brooks, David H.; Cirtain, Jonathan W.; De Pontieu, Bart; Golub,
   Leon; Kobayashi, Ken; McKenzie, David E.; Morton, Richard J.; Peter,
   Hardi; Rachmeler, Laurel A.; Savage, Sabrina L.; Testa, Paola; Tiwari,
   Sanjiv K.; Warren, Harry P.; Watkinson, Benjamin J.
Bibcode: 2020ApJ...892..134W
Altcode: 2020arXiv200111254W
  Following the success of the first mission, the High-Resolution
  Coronal Imager (Hi-C) was launched for a third time (Hi-C 2.1)
  on 2018 May 29 from the White Sands Missile Range, NM, USA. On this
  occasion, 329 s of 17.2 nm data of target active region AR 12712 were
  captured with a cadence of ≈4 s, and a plate scale of 0.129 arcsec
  pixel<SUP>-1</SUP>. Using data captured by Hi-C 2.1 and co-aligned
  observations from SDO/AIA 17.1 nm, we investigate the widths of 49
  coronal strands. We search for evidence of substructure within the
  strands that is not detected by AIA, and further consider whether these
  strands are fully resolved by Hi-C 2.1. With the aid of multi-scale
  Gaussian normalization, strands from a region of low emission that can
  only be visualized against the contrast of the darker, underlying moss
  are studied. A comparison is made between these low-emission strands
  and those from regions of higher emission within the target active
  region. It is found that Hi-C 2.1 can resolve individual strands as
  small as ≈202 km, though the more typical strand widths seen are
  ≈513 km. For coronal strands within the region of low emission, the
  most likely width is significantly narrower than the high-emission
  strands at ≈388 km. This places the low-emission coronal strands
  beneath the resolving capabilities of SDO/AIA, highlighting the need
  for a permanent solar observatory with the resolving power of Hi-C.

Title: A chromospheric resonance cavity in a sunspot mapped with
    seismology
Authors: Jess, David B.; Snow, Ben; Houston, Scott J.; Botha, Gert
   J. J.; Fleck, Bernhard; Krishna Prasad, S.; Asensio Ramos, Andrés;
   Morton, Richard J.; Keys, Peter H.; Jafarzadeh, Shahin; Stangalini,
   Marco; Grant, Samuel D. T.; Christian, Damian J.
Bibcode: 2020NatAs...4..220J
Altcode: 2019NatAs...4..220J; 2019NatAs.tmp..502J
  Sunspots are intense collections of magnetic fields that pierce through
  the Sun's photosphere, with their signatures extending upwards into the
  outermost extremities of the solar corona<SUP>1</SUP>. Cutting-edge
  observations and simulations are providing insights into the
  underlying wave generation<SUP>2</SUP>, configuration<SUP>3,4</SUP> and
  damping<SUP>5</SUP> mechanisms found in sunspot atmospheres. However,
  the in situ amplification of magnetohydrodynamic waves<SUP>6</SUP>,
  rising from a few hundreds of metres per second in the photosphere to
  several kilometres per second in the chromosphere<SUP>7</SUP>, has,
  until now, proved difficult to explain. Theory predicts that the
  enhanced umbral wave power found at chromospheric heights may come
  from the existence of an acoustic resonator<SUP>8-10</SUP>, which
  is created due to the substantial temperature gradients experienced
  at photospheric and transition region heights<SUP>11</SUP>. Here,
  we provide strong observational evidence of a resonance cavity
  existing above a highly magnetic sunspot. Through a combination of
  spectropolarimetric inversions and comparisons with high-resolution
  numerical simulations, we provide a new seismological approach to
  mapping the geometry of the inherent temperature stratifications across
  the diameter of the underlying sunspot, with the upper boundaries of the
  chromosphere ranging between 1,300 ± 200 km and 2,300 ± 250 km. Our
  findings will allow the three-dimensional structure of solar active
  regions to be conclusively determined from relatively commonplace
  two-dimensional Fourier power spectra. The techniques presented are
  also readily suitable for investigating temperature-dependent resonance
  effects in other areas of astrophysics, including the examination of
  Earth-ionosphere wave cavities<SUP>12</SUP>.

Title: Hi-C 2.1 Observations of Jetlet-like Events at Edges of Solar
    Magnetic Network Lanes
Authors: Panesar, Navdeep K.; Sterling, Alphonse C.; Moore, Ronald L.;
   Winebarger, Amy R.; Tiwari, Sanjiv K.; Savage, Sabrina L.; Golub, Leon
   E.; Rachmeler, Laurel A.; Kobayashi, Ken; Brooks, David H.; Cirtain,
   Jonathan W.; De Pontieu, Bart; McKenzie, David E.; Morton, Richard J.;
   Peter, Hardi; Testa, Paola; Walsh, Robert W.; Warren, Harry P.
Bibcode: 2019ApJ...887L...8P
Altcode: 2019arXiv191102331P
  We present high-resolution, high-cadence observations of six,
  fine-scale, on-disk jet-like events observed by the High-resolution
  Coronal Imager 2.1 (Hi-C 2.1) during its sounding-rocket flight. We
  combine the Hi-C 2.1 images with images from the Solar Dynamics
  Observatory (SDO)/Atmospheric Imaging Assembly (AIA) and the Interface
  Region Imaging Spectrograph (IRIS), and investigate each event’s
  magnetic setting with co-aligned line-of-sight magnetograms from the
  SDO/Helioseismic and Magnetic Imager (HMI). We find that (i) all six
  events are jetlet-like (having apparent properties of jetlets), (ii)
  all six are rooted at edges of magnetic network lanes, (iii) four of
  the jetlet-like events stem from sites of flux cancelation between
  majority-polarity network flux and merging minority-polarity flux, and
  (iv) four of the jetlet-like events show brightenings at their bases
  reminiscent of the base brightenings in coronal jets. The average
  spire length of the six jetlet-like events (9000 ± 3000 km) is three
  times shorter than that for IRIS jetlets (27,000 ± 8000 km). While
  not ruling out other generation mechanisms, the observations suggest
  that at least four of these events may be miniature versions of both
  larger-scale coronal jets that are driven by minifilament eruptions
  and still-larger-scale solar eruptions that are driven by filament
  eruptions. Therefore, we propose that our Hi-C events are driven by
  the eruption of a tiny sheared-field flux rope, and that the flux rope
  field is built and triggered to erupt by flux cancelation.

Title: Fine-scale Explosive Energy Release at Sites of Prospective
    Magnetic Flux Cancellation in the Core of the Solar Active Region
    Observed by Hi-C 2.1, IRIS, and SDO
Authors: Tiwari, Sanjiv K.; Panesar, Navdeep K.; Moore, Ronald L.;
   De Pontieu, Bart; Winebarger, Amy R.; Golub, Leon; Savage, Sabrina L.;
   Rachmeler, Laurel A.; Kobayashi, Ken; Testa, Paola; Warren, Harry P.;
   Brooks, David H.; Cirtain, Jonathan W.; McKenzie, David E.; Morton,
   Richard J.; Peter, Hardi; Walsh, Robert W.
Bibcode: 2019ApJ...887...56T
Altcode: 2019arXiv191101424T
  The second Hi-C flight (Hi-C 2.1) provided unprecedentedly high spatial
  and temporal resolution (∼250 km, 4.4 s) coronal EUV images of Fe IX/X
  emission at 172 Å of AR 12712 on 2018 May 29, during 18:56:21-19:01:56
  UT. Three morphologically different types (I: dot-like; II: loop-like;
  III: surge/jet-like) of fine-scale sudden-brightening events (tiny
  microflares) are seen within and at the ends of an arch filament system
  in the core of the AR. Although type Is (not reported before) resemble
  IRIS bombs (in size, and brightness with respect to surroundings),
  our dot-like events are apparently much hotter and shorter in span
  (70 s). We complement the 5 minute duration Hi-C 2.1 data with SDO/HMI
  magnetograms, SDO/AIA EUV images, and IRIS UV spectra and slit-jaw
  images to examine, at the sites of these events, brightenings and
  flows in the transition region and corona and evolution of magnetic
  flux in the photosphere. Most, if not all, of the events are seated
  at sites of opposite-polarity magnetic flux convergence (sometimes
  driven by adjacent flux emergence), implying likely flux cancellation
  at the microflare’s polarity inversion line. In the IRIS spectra
  and images, we find confirming evidence of field-aligned outflow from
  brightenings at the ends of loops of the arch filament system. In types
  I and II the explosion is confined, while in type III the explosion
  is ejective and drives jet-like outflow. The light curves from Hi-C,
  AIA, and IRIS peak nearly simultaneously for many of these events,
  and none of the events display a systematic cooling sequence as seen in
  typical coronal flares, suggesting that these tiny brightening events
  have chromospheric/transition region origin.

Title: The High-Resolution Coronal Imager, Flight 2.1
Authors: Rachmeler, Laurel A.; Winebarger, Amy R.; Savage, Sabrina L.;
   Golub, Leon; Kobayashi, Ken; Vigil, Genevieve D.; Brooks, David H.;
   Cirtain, Jonathan W.; De Pontieu, Bart; McKenzie, David E.; Morton,
   Richard J.; Peter, Hardi; Testa, Paola; Tiwari, Sanjiv K.; Walsh,
   Robert W.; Warren, Harry P.; Alexander, Caroline; Ansell, Darren;
   Beabout, Brent L.; Beabout, Dyana L.; Bethge, Christian W.; Champey,
   Patrick R.; Cheimets, Peter N.; Cooper, Mark A.; Creel, Helen K.;
   Gates, Richard; Gomez, Carlos; Guillory, Anthony; Haight, Harlan;
   Hogue, William D.; Holloway, Todd; Hyde, David W.; Kenyon, Richard;
   Marshall, Joseph N.; McCracken, Jeff E.; McCracken, Kenneth; Mitchell,
   Karen O.; Ordway, Mark; Owen, Tim; Ranganathan, Jagan; Robertson,
   Bryan A.; Payne, M. Janie; Podgorski, William; Pryor, Jonathan; Samra,
   Jenna; Sloan, Mark D.; Soohoo, Howard A.; Steele, D. Brandon; Thompson,
   Furman V.; Thornton, Gary S.; Watkinson, Benjamin; Windt, David
Bibcode: 2019SoPh..294..174R
Altcode: 2019arXiv190905942R
  The third flight of the High-Resolution Coronal Imager (Hi-C 2.1)
  occurred on May 29, 2018; the Sounding Rocket was launched from White
  Sands Missile Range in New Mexico. The instrument has been modified
  from its original configuration (Hi-C 1) to observe the solar corona
  in a passband that peaks near 172 Å, and uses a new, custom-built
  low-noise camera. The instrument targeted Active Region 12712, and
  captured 78 images at a cadence of 4.4 s (18:56:22 - 19:01:57 UT; 5
  min and 35 s observing time). The image spatial resolution varies due
  to quasi-periodic motion blur from the rocket; sharp images contain
  resolved features of at least 0.47 arcsec. There are coordinated
  observations from multiple ground- and space-based telescopes providing
  an unprecedented opportunity to observe the mass and energy coupling
  between the chromosphere and the corona. Details of the instrument
  and the data set are presented in this paper.

Title: Investigating “Dark” Energy in the Solar Corona Using
    Forward Modeling of MHD Waves
Authors: Pant, Vaibhav; Magyar, Norbert; Van Doorsselaere, Tom;
   Morton, Richard J.
Bibcode: 2019ApJ...881...95P
Altcode: 2019arXiv190610941P
  It is now well established that Alfvénic waves are ubiquitous in the
  solar corona. However, the Alfvénic wave energy estimated from Doppler
  velocity measurements in the corona was found to be four orders of
  magnitude less than that estimated from nonthermal line widths. McIntosh
  &amp; De Pontieu suggested that this discrepancy in energy might be
  due to the line-of-sight (LOS) superposition of several oscillating
  structures, which can lead to an underestimation of the Alfvénic
  wave amplitudes and energies. McIntosh &amp; De Pontieu termed this
  coronal “dark” or “hidden” energy. However, their simulations
  required the use of an additional, unknown source of Alfvénic
  wave energy to obtain agreement with measurements of the coronal
  nonthermal line widths. In this study, we investigate the requirement
  of this unknown source of additional “dark” energy in the solar
  corona using gravitationally stratified 3D magnetohydrodynamic (MHD)
  simulations of propagating waves. We excite the transverse MHD waves
  and generate synthetic observations of the Fe XIII emission line. We
  establish that LOS superposition greatly reduces the Doppler velocity
  amplitudes and increases the nonthermal line widths. Importantly, our
  model generates the observed wedge-shape correlation between Doppler
  velocities and nonthermal line widths. We find that the observed wave
  energy is only 0.2%-1% of the true wave energy, which explains the
  2-3 order-of-magnitude energy discrepancy. We conclusively establish
  that true wave energies are hidden in nonthermal line widths. Hence,
  our results rule out the requirement for an additional “dark”
  energy in the solar corona.

Title: Exploring the Properties of Transverse Waves at the Base of
    the Solar Wind
Authors: Weberg, Micah J.; Morton, Richard; McLaughlin, James; Laming,
   Martin; Ko, Yuan-Kuen
Bibcode: 2019shin.confE.173W
Altcode:
  Transverse (or ‘Alfvénic’) waves are commonly invoked by
  theories and models to explain coronal heating and solar wind
  acceleration. However, direct measurements are sparse and most of
  what we know is derived from indirect proxies for wave activity. In
  this study, we present a large, statistical study of transverse waves
  directly observed in coronal plumes between May 2010 and May 2019
  by SDO / AIA. The data was processed using an automated version of
  the Northumbria University Wave Tracking Code (NUWT) and presents a
  detailed picture of wave properties at the base of the solar wind. We
  find that the bulk wave parameters within the time periods analysed
  are largely consistent over most of a solar cycle. However, there is
  some evidence for smaller-scale variations with height, latitude, and
  over time periods of a few years. We will also explore the possibility
  of frequency-dependant processes which may give limits on the height
  at which wave dissipation, and thereby solar wind acceleration,
  begins. Lastly, we will give estimates for the total energy flux
  contained in the waves and discuss how it compares to the energy
  required to accelerate the solar wind.

Title: Damping of Propagating Kink Waves in the Solar Corona
Authors: Tiwari, Ajay K.; Morton, Richard J.; Régnier, Stéphane;
   McLaughlin, James A.
Bibcode: 2019ApJ...876..106T
Altcode: 2019arXiv190408834T
  Alfvénic waves have gained renewed interest since the existence of
  ubiquitous propagating kink waves were discovered in the corona. It
  has long been suggested that Alfvénic waves play an important role
  in coronal heating and the acceleration of the solar wind. To this
  effect, it is imperative to understand the mechanisms that enable their
  energy to be transferred to the plasma. Mode conversion via resonant
  absorption is believed to be one of the main mechanisms for kink wave
  damping and it is considered to play a key role in the process of energy
  transfer. This study examines the damping of propagating kink waves in
  quiescent coronal loops using the Coronal Multi-channel Polarimeter. A
  coherence-based method is used to track the Doppler velocity signal
  of the waves, which enables us to investigate the spatial evolution of
  velocity perturbations. The power ratio of outward to inward propagating
  waves is used to estimate the associated damping lengths and quality
  factors. To enable accurate estimates of these quantities, we provide
  the first derivation of a likelihood function suitable for fitting
  models to the ratio of two power spectra obtained from discrete Fourier
  transforms. Maximum likelihood estimation is used to fit an exponential
  damping model to the observed variation in power ratio as a function
  of frequency. We confirm earlier indications that propagating kink
  waves are undergoing frequency-dependent damping. Additionally, we find
  that the rate of damping decreases, or equivalently the damping length
  increases, for longer coronal loops that reach higher in the corona.

Title: A basal contribution from p-modes to the Alfvénic wave flux
    in the Sun's corona
Authors: Morton, R. J.; Weberg, M. J.; McLaughlin, J. A.
Bibcode: 2019NatAs...3..223M
Altcode: 2019arXiv190203811M; 2019NatAs.tmp..196M
  Many cool stars possess complex magnetic fields<SUP>1</SUP> that are
  considered to undertake a central role in the structuring and energizing
  of their atmospheres<SUP>2</SUP>. Alfvénic waves are thought to
  make a critical contribution to energy transfer along these magnetic
  fields, with the potential to heat plasma and accelerate stellar
  winds<SUP>3-5</SUP>. Despite Alfvénic waves having been identified
  in the Sun's atmosphere, the nature of the basal wave energy flux
  is poorly understood. It is generally assumed that the associated
  Poynting flux is generated solely in the photosphere and propagates
  into the corona, typically through the continuous buffeting of magnetic
  fields by turbulent convective cells<SUP>4,6,7</SUP>. Here, we provide
  evidence that the Sun's internal acoustic modes also contribute to
  the basal flux of Alfvénic waves, delivering a spatially ubiquitous
  input to the coronal energy balance that is sustained over the solar
  cycle. Alfvénic waves are thus a fundamental feature of the Sun's
  corona. Acknowledging that internal acoustic modes have a key role
  in injecting additional Poynting flux into the upper atmospheres
  of Sun-like stars has potentially significant consequences for the
  modelling of stellar coronae and winds.

Title: Variation of Doppler velocity with non-thermal line width in
    a gravitationally stratified plasma
Authors: Pant, Vaibhav; Magyar, Norbert; Van Doorsselaere, Tom;
   Morton, Richard
Bibcode: 2018csc..confE..70P
Altcode:
  Magnetohydrodynamic (MHD) waves are ubiquitous in the solar
  atmosphere. These waves play an important role in the heating of
  solar corona. Recently, an apparent discrepancy is observed in the
  Alfvénic wave amplitudes measured by the Coronal Multi-channel
  Polarimeter (CoMP) compared to those measured by the Hinode and the
  Solar Dynamics Observatory (SDO). This discrepancy was attributed
  to a large line-of-sight superposition and low spatial resolution of
  the CoMP, which may lead to low wave amplitudes and large non-thermal
  line widths. A wedge-shape correlation is also observed between root
  mean square Doppler velocity and mean non-thermal line width. We
  investigate this scenario by performing a 3D MHD simulation of a
  gravitationally stratified transversely inhomogenous plasma subjected
  to the unidirectionally propagating MHD waves. Here, we present the
  results of this simulation forward modelled with the FoMo for Fe XIII
  (10747 Å) emission line to study the variation of Doppler velocities
  with non-thermal line widths. We perform the random integration over
  different line-of-sights angles across and along the simulation box. We
  degrade the spatial resolution of the simulation box to the spatial
  resolution of the CoMP and compare Doppler velocities and non-thermal
  line widths at different heights. We compare our results with previous
  studies as well as with observations made by the CoMP and find a fairly
  good match between them.

Title: Photospheric Observations of Surface and Body Modes in Solar
    Magnetic Pores
Authors: Keys, Peter H.; Morton, Richard J.; Jess, David B.; Verth,
   Gary; Grant, Samuel D. T.; Mathioudakis, Mihalis; Mackay, Duncan H.;
   Doyle, John G.; Christian, Damian J.; Keenan, Francis P.; Erdélyi,
   Robertus
Bibcode: 2018ApJ...857...28K
Altcode: 2018arXiv180301859K
  Over the past number of years, great strides have been made in
  identifying the various low-order magnetohydrodynamic wave modes
  observable in a number of magnetic structures found within the solar
  atmosphere. However, one aspect of these modes that has remained
  elusive, until now, is their designation as either surface or body
  modes. This property has significant implications for how these modes
  transfer energy from the waveguide to the surrounding plasma. Here, for
  the first time to our knowledge, we present conclusive, direct evidence
  of these wave characteristics in numerous pores that were observed to
  support sausage modes. As well as outlining methods to detect these
  modes in observations, we make estimates of the energies associated
  with each mode. We find surface modes more frequently in the data,
  as well as that surface modes appear to carry more energy than those
  displaying signatures of body modes. We find frequencies in the range
  of ∼2-12 mHz, with body modes as high as 11 mHz, but we do not find
  surface modes above 10 mHz. It is expected that the techniques we have
  applied will help researchers search for surface and body signatures
  in other modes and in differing structures from those presented here.

Title: An Automated Algorithm for Identifying and Tracking Transverse
    Waves in Solar Images
Authors: Weberg, Micah J.; Morton, Richard J.; McLaughlin, James A.
Bibcode: 2018ApJ...852...57W
Altcode: 2018arXiv180704842W
  Recent instrumentation has demonstrated that the solar atmosphere
  supports omnipresent transverse waves, which could play a key role
  in energizing the solar corona. Large-scale studies are required
  in order to build up an understanding of the general properties
  of these transverse waves. To help facilitate this, we present an
  automated algorithm for identifying and tracking features in solar
  images and extracting the wave properties of any observed transverse
  oscillations. We test and calibrate our algorithm using a set of
  synthetic data, which includes noise and rotational effects. The
  results indicate an accuracy of 1%-2% for displacement amplitudes
  and 4%-10% for wave periods and velocity amplitudes. We also apply
  the algorithm to data from the Atmospheric Imaging Assembly on board
  the Solar Dynamics Observatory and find good agreement with previous
  studies. Of note, we find that 35%-41% of the observed plumes exhibit
  multiple wave signatures, which indicates either the superposition
  of waves or multiple independent wave packets observed at different
  times within a single structure. The automated methods described
  in this paper represent a significant improvement on the speed and
  quality of direct measurements of transverse waves within the solar
  atmosphere. This algorithm unlocks a wide range of statistical studies
  that were previously impractical.

Title: Annual Properties of Transverse Waves in the Corona over most
    of Solar Cycle 24
Authors: Weberg, M. J.; Morton, R. J.; McLaughlin, J. A.
Bibcode: 2017AGUFMSH42B..07W
Altcode:
  Waves are an omnipresent feature in heliophysical plasmas. In
  particular, transverse (or "Alfvénic") waves have been observed at a
  wide range of spatial and temporal scales within the corona and solar
  wind. These waves play a key role in transporting energy through the
  solar atmosphere and are also thought to contribute to the heating and
  acceleration of the solar wind. Previous studies of low-frequency (&lt;
  10 mHz) transverse waves in coronal loops and polar plumes have provided
  tantalizing glimpses at specific time periods, however few, if any,
  systematic studies have been performed spanning long time scales. In
  this study, we combine recent advancements in the automated detection
  and measurement of low-frequency transverse waves with over 7 years
  of SDO / AIA data to provide a detailed picture of coronal transverse
  waves in polar plumes and, for the first time, begin to examine their
  long-term behaviour. We measure waves at three different heights in
  each of eight, four-hour periods spanning May 2010 - May 2017. We
  find that the bulk wave parameters within these 24 regions are largely
  consistent over most of a solar cycle. However, there is some evidence
  for smaller-scale variations both with height and over time periods
  of a few years. We also discuss total energy flux estimations based
  on the full wave power spectra, which yields a more nuanced picture
  than previous values based on summary statistics. Overall, this work
  expands our view of wave processes in the corona and is relevant to
  both theoretical and modelling considerations of energy transport
  within the solar atmosphere. Crucially, these initial results suggest
  that the energy flux provided by the low-frequency transverse waves
  varies little over the solar cycle, potentially indicating that the
  waves provide a consistent source of energy to the corona and beyond.

Title: Measuring the magnetic field of a trans-equatorial loop system
    using coronal seismology (Corrigendum)
Authors: Long, D. M.; Valori, G.; Pérez-Suárez, D.; Morton, R. J.;
   Vásquez, A. M.
Bibcode: 2017A&A...607C...3L
Altcode:
  No abstract at ADS

Title: Design and development by direct polishing of the WFXT thin
    polynomial mirror shells
Authors: Proserpio, L.; Campana, S.; Citterio, O.; Civitani, M.;
   Combrinck, H.; Conconi, P.; Cotroneo, V.; Freeman, R.; Mattini,
   E.; Langstrof, P.; Morton, R.; Motta, G.; Oberle, O.; Pareschi, G.;
   Parodi, G.; Pels, C.; Schenk, C.; Stock, R.; Tagliaferri, G.
Bibcode: 2017SPIE10565E..2NP
Altcode:
  The Wide Field X-ray Telescope (WFXT) is a medium class mission proposed
  to address key questions about cosmic origins and physics of the cosmos
  through an unprecedented survey of the sky in the soft X-ray band
  (0.2-6 keV) [1], [2]. In order to get the desired angular resolution of
  10 arcsec (5 arcsec goal) on the entire 1 degrees Field Of View (FOV),
  the design of the optical system is based on nested grazing-incidence
  polynomial profiles mirrors, and assumes a focal plane curvature and
  plate scale corrections among the shells. This design guarantees an
  increased angular resolution also at large off-axis positions with
  respect to the usually adopted Wolter I configuration. In order to
  meet the requirements in terms of mass and effective area (less than
  1200 kg, 6000 cm<SUP>2</SUP> @ 1 keV), the nested shells are thin
  and made of quartz glass. The telescope assembly is composed by three
  identical modules of 78 nested shells each, with diameter up to 1.1
  m, length in the range of 200-440 mm and thickness of less than 2.2
  mm. At this regard, a deterministic direct polishing method is under
  investigation to manufacture the WFXT thin grazing-incidence mirrors
  made of quartz. The direct polishing method has already been used for
  past missions (as Einstein, Rosat, Chandra) but based on much thicker
  shells (10 mm ore more). The technological challenge for WFXT is to
  apply the same approach but for 510 times thinner shells. The proposed
  approach is based on two main steps: first, quartz glass tubes available
  on the market are ground to conical profiles; second the pre-shaped
  shells are polished to the required polynomial profiles using a CNC
  polishing machine. In this paper, preliminary results on the direct
  grinding and polishing of prototypes shells made by quartz glass with
  low thickness, representative of the WFXT optical design, are presented.

Title: Dynamics of internetwork chromospheric fibrils: Basic
    properties and magnetohydrodynamic kink waves
Authors: Mooroogen, K.; Morton, R. J.; Henriques, V.
Bibcode: 2017A&A...607A..46M
Altcode: 2017arXiv170803500M
  <BR /> Aims: Current observational instruments are now providing
  data with the necessary temporal and spatial cadences required to
  examine highly dynamic, fine-scale magnetic structures in the solar
  atmosphere. Using the spectroscopic imaging capabilities of the
  Swedish Solar Telescope, we aim to provide the first investigation on
  the nature and dynamics of elongated absorption features (fibrils)
  observed in Hα in the internetwork. <BR /> Methods: We observe and
  identify a number of internetwork fibrils, which form away from the
  kilogauss, network magnetic flux, and we provide a synoptic view
  on their behaviour. The internetwork fibrils are found to support
  wave-like behaviour, which we interpret as magnetohydrodynamic (MHD)
  kink waves. The properties of these waves, that is, amplitude, period,
  and propagation speed, are measured from time-distance diagrams and we
  attempt to exploit them via magneto-seismology in order to probe the
  variation of plasma properties along the wave-guides. <BR /> Results:
  We found that the Internetwork (IN) fibrils appear, disappear, and
  re-appear on timescales of tens of minutes, suggesting that they
  are subject to repeated heating. No clear photospheric footpoints
  for the fibrils are found in photospheric magnetograms or Hα wing
  images. However, we suggest that they are magnetised features as the
  majority of them show evidence of supporting propagating MHD kink
  waves, with a modal period of 120 s. Additionally, one IN fibril is
  seen to support a flow directed along its elongated axis, suggesting
  a guiding field. The wave motions are found to propagate at speeds
  significantly greater than estimates for typical chromospheric sound
  speeds. Through their interpretation as kink waves, the measured speeds
  provide an estimate for local average Alfvén speeds. Furthermore,
  the amplitudes of the waves are also found to vary as a function of
  distance along the fibrils, which can be interpreted as evidence of
  stratification of the plasma in the neighbourhood of the IN fibril.

Title: The Frequency-dependent Damping of Slow Magnetoacoustic Waves
    in a Sunspot Umbral Atmosphere
Authors: Krishna Prasad, S.; Jess, D. B.; Van Doorsselaere, T.; Verth,
   G.; Morton, R. J.; Fedun, V.; Erdélyi, R.; Christian, D. J.
Bibcode: 2017ApJ...847....5K
Altcode: 2017ApJ...847....5P; 2017arXiv170804835K
  High spatial and temporal resolution images of a sunspot,
  obtained simultaneously in multiple optical and UV wavelengths, are
  employed to study the propagation and damping characteristics of slow
  magnetoacoustic waves up to transition region heights. Power spectra are
  generated from intensity oscillations in sunspot umbra, across multiple
  atmospheric heights, for frequencies up to a few hundred mHz. It is
  observed that the power spectra display a power-law dependence over
  the entire frequency range, with a significant enhancement around 5.5
  mHz found for the chromospheric channels. The phase difference spectra
  reveal a cutoff frequency near 3 mHz, up to which the oscillations
  are evanescent, while those with higher frequencies propagate
  upward. The power-law index appears to increase with atmospheric
  height. Also, shorter damping lengths are observed for oscillations
  with higher frequencies suggesting frequency-dependent damping. Using
  the relative amplitudes of the 5.5 mHz (3 minute) oscillations, we
  estimate the energy flux at different heights, which seems to decay
  gradually from the photosphere, in agreement with recent numerical
  simulations. Furthermore, a comparison of power spectra across the
  umbral radius highlights an enhancement of high-frequency waves near
  the umbral center, which does not seem to be related to magnetic field
  inclination angle effects.

Title: Measuring the magnetic field of a trans-equatorial loop system
    using coronal seismology
Authors: Long, D. M.; Valori, G.; Pérez-Suárez, D.; Morton, R. J.;
   Vásquez, A. M.
Bibcode: 2017A&A...603A.101L
Altcode: 2017arXiv170310020L
  Context. EIT waves are freely-propagating global pulses in the low
  corona which are strongly associated with the initial evolution of
  coronal mass ejections (CMEs). They are thought to be large-amplitude,
  fast-mode magnetohydrodynamic waves initially driven by the rapid
  expansion of a CME in the low corona. <BR /> Aims: An EIT wave was
  observed on 6 July 2012 to impact an adjacent trans-equatorial loop
  system which then exhibited a decaying oscillation as it returned to
  rest. Observations of the loop oscillations were used to estimate the
  magnetic field strength of the loop system by studying the decaying
  oscillation of the loop, measuring the propagation of ubiquitous
  transverse waves in the loop and extrapolating the magnetic field
  from observed magnetograms. <BR /> Methods: Observations from the
  Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory
  (SDO/AIA) and the Coronal Multi-channel Polarimeter (CoMP) were used
  to study the event. An Empirical Mode Decomposition analysis was used
  to characterise the oscillation of the loop system in CoMP Doppler
  velocity and line width and in AIA intensity. <BR /> Results: The
  loop system was shown to oscillate in the 2nd harmonic mode rather
  than at the fundamental frequency, with the seismological analysis
  returning an estimated magnetic field strength of ≈ 5.5 ± 1.5
  G. This compares to the magnetic field strength estimates of ≈1-9
  G and ≈3-9 G found using the measurements of transverse wave
  propagation and magnetic field extrapolation respectively. <P
  />A movie associated to Figs. 1 and 2 is available at <A
  href="http://www.aanda.org/10.1051/0004-6361/201730413/olm">http://www.aanda.org</A>

Title: Observational Signatures of a Kink-unstable Coronal Flux Rope
    Using Hinode/EIS
Authors: Snow, B.; Botha, G. J. J.; Régnier, S.; Morton, R. J.;
   Verwichte, E.; Young, P. R.
Bibcode: 2017ApJ...842...16S
Altcode: 2017arXiv170505114S
  The signatures of energy release and energy transport for a
  kink-unstable coronal flux rope are investigated via forward
  modeling. Synthetic intensity and Doppler maps are generated from
  a 3D numerical simulation. The CHIANTI database is used to compute
  intensities for three Hinode/EIS emission lines that cover the
  thermal range of the loop. The intensities and Doppler velocities at
  simulation-resolution are spatially degraded to the Hinode/EIS pixel
  size (1″), convolved using a Gaussian point-spread function (3″),
  and exposed for a characteristic time of 50 s. The synthetic images
  generated for rasters (moving slit) and sit-and-stare (stationary
  slit) are analyzed to find the signatures of the twisted flux and the
  associated instability. We find that there are several qualities of a
  kink-unstable coronal flux rope that can be detected observationally
  using Hinode/EIS, namely the growth of the loop radius, the increase in
  intensity toward the radial edge of the loop, and the Doppler velocity
  following an internal twisted magnetic field line. However, EIS cannot
  resolve the small, transient features present in the simulation,
  such as sites of small-scale reconnection (e.g., nanoflares).

Title: Project SunbYte: solar astronomy on a budget
Authors: Alvarez Gonzalez, F.; Badilita, A. -M.; Baker, A.; Cho,
   Y. -H.; Dhot, N.; Fedun, V.; Hare, C.; He, T.; Hobbs, M.; Javed,
   M.; Lovesey, H.; Lord, C.; Panoutsos, G.; Permyakov, A.; Pope, S.;
   Portnell, M.; Rhodes, L.; Sharma, R.; Taras, P.; Taylor, J.; Tilbrook,
   R.; Verth, G.; Wrigley, S. N.; Yaqoob, M.; Cook, R.; McLaughlin, J.;
   Morton, R.; Scullion, E.; Shelyag, S.; Hamilton, A.; Zharkov, S.;
   Jess, D.; Wrigley, M.
Bibcode: 2017A&G....58d2.24A
Altcode:
  The Sheffield University Nova Balloon Lifted Solar Telescope (SunbYte)
  is a high-altitude balloon experiment devised and run largely by
  students at the University of Sheffield, and is scheduled for launch
  in October 2017. It was the only UK project in 2016 to be selected for
  the balloon side of the Swedish-German student programme REXUS/BEXUS
  (Rocket and Balloon Experiments for University Students; see box on
  p2.25). The success of the SunbYte team in the REXUS/BEXUS selection
  process is an unprecedented opportunity for the students to gain
  valuable experience working in the space engineering industry, using
  their theoretical knowledge and networking with students and technology
  companies from all over Europe.

Title: Automating Direct Observations of Transverse Waves in the
    Solar Corona
Authors: Weberg, M. J.; Morton, R. J.; McLaughlin, J. A.
Bibcode: 2016AGUFMSH21E2576W
Altcode:
  A multitude of MHD waves have been observed at a large range of scales
  in the solar atmosphere. According to theories and models, transverse
  (or "Alfvénic") waves are a viable mechanism for both heating and
  accelerating the solar wind and may also drive certain elemental
  fractionation processes in the chromosphere and corona. However,
  direct measurements of transverse waves in polar plumes (Thurgood
  et al. 2014) have raised some questions concerning the total energy
  carried by the waves and whether or not it is sufficient to be a
  primary driver of either solar wind heating or acceleration. In
  this work we build upon on the framework of Morton &amp; McLaughlin
  (2013) and Thurgood et al. (2014) and extend the capabilities of the
  Northumbria University Wave Tracking (NUWT) code. In particular, we
  present an automated method of detecting and quantifying transverse
  waves in polar coronal holes. With the application of Fourier analysis
  methods, we investigate the superposition of multiple waves propagating
  along individual structures and, additionally, examine multi-variate
  relationships that may exist between wave parameters. We report the
  distributions of wave parameters for hundreds of waves observed using
  data from the 171 Å channel of SDO / AIA at select times throughout
  the solar cycle. Finally, we discuss how the measured average wave
  energy compares to theoretical predictions. The methods described in
  this research can be easily applied to other instruments, both space-
  and ground-based, and the observations of wave parameters and energetics
  place important constraints on wave-driven models of the solar corona.

Title: The importance of high-resolution observations of the solar
    corona
Authors: Winebarger, A. R.; Cirtain, J. W.; Golub, L.; Walsh, R. W.;
   De Pontieu, B.; Savage, S. L.; Rachmeler, L.; Kobayashi, K.; Testa,
   P.; Brooks, D.; Warren, H.; Mcintosh, S. W.; Peter, H.; Morton, R. J.;
   Alexander, C. E.; Tiwari, S. K.
Bibcode: 2016AGUFMSH31B2577W
Altcode:
  The spatial and temporal resolutions of the available coronal
  observatories are inadequate to resolve the signatures of coronal
  heating. High-resolution and high-cadence observations available with
  the Interface Region Imaging Spectrograph (IRIS) and the High-resolution
  Coronal Imager (Hi-C) instrument hint that 0.3 arcsec resolution images
  and &lt; 10 s cadence provide the necessary resolution to detect
  heating events. Hi-C was launched from White Sands Missile Range on
  July 11, 2012 (before the launch with IRIS) and obtained images of
  a solar active region in the 19.3 nm passband. In this presentation,
  I will discuss the potential of combining a flight in Hi-C with a 17.1
  nm passband, in conjunction with IRIS. This combination will provide,
  for the first time, a definitive method of tracing the energy flow
  between the chromosphere and corona and vice versa.

Title: Exploring Coronal Dynamics: A Next Generation Solar Physics
    Mission white paper
Authors: Morton, R. J.; Scullion, E.; Bloomfield, D. S.; McLaughlin,
   J. A.; Regnier, S.; McIntosh, S. W.; Tomczyk, S.; Young, P.
Bibcode: 2016arXiv161106149M
Altcode:
  Determining the mechanisms responsible for the heating of the
  coronal plasma and maintaining and accelerating the solar wind
  are long standing goals in solar physics. There is a clear need to
  constrain the energy, mass and momentum flux through the solar corona
  and advance our knowledge of the physical process contributing to
  these fluxes. Furthermore, the accurate forecasting of Space Weather
  conditions at the near-Earth environment and, more generally, the
  plasma conditions of the solar wind throughout the heliosphere, require
  detailed knowledge of these fluxes in the near-Sun corona. Here we
  present a short case for a space-based imaging-spectrometer coronagraph,
  which will have the ability to provide synoptic information on the
  coronal environment and provide strict constraints on the mass, energy,
  and momentum flux through the corona. The instrument would ideally
  achieve cadences of $\sim10$~s, spatial resolution of 1" and observe the
  corona out to 2~$R_{\sun}$. Such an instrument will enable significant
  progress in our understanding of MHD waves throughout complex plasmas,
  as well as potentially providing routine data products to aid Space
  Weather forecasting.

Title: A Global View of Velocity Fluctuations in the Corona below
    1.3 R <SUB>⊙</SUB> with CoMP
Authors: Morton, R. J.; Tomczyk, S.; Pinto, R. F.
Bibcode: 2016ApJ...828...89M
Altcode: 2016arXiv160801831M
  The Coronal Multi-channel Polarimeter (CoMP) has previously demonstrated
  the presence of Doppler velocity fluctuations in the solar corona. The
  observed fluctuations are thought to be transverse waves, I.e., highly
  incompressible motions whose restoring force is dominated by the
  magnetic tension, some of which demonstrate clear periodicity. We aim
  to exploit CoMP’s ability to provide high cadence observations of the
  off-limb corona to investigate the properties of velocity fluctuations
  in a range of coronal features, providing insight into how (whether)
  the properties of the waves are influenced by the varying magnetic
  topology in active regions, quiet Sun and open field regions. An
  analysis of Doppler velocity time-series of the solar corona from
  the 10747 Å Iron xiii line is performed, determining the velocity
  power spectrum and using it as a tool to probe wave behavior. Further,
  the average phase speed and density for each region are estimated and
  used to compute the spectra for energy density and energy flux. In
  addition, we assess the noise levels associated with the CoMP data,
  deriving analytic formulae for the uncertainty on Doppler velocity
  measurements and providing a comparison by estimating the noise
  from the data. It is found that the entire corona is replete with
  transverse wave behavior. The corresponding power spectra indicate
  that the observed velocity fluctuations are predominately generated
  by stochastic processes, with the spectral slope of the power varying
  between the different magnetic regions. Most strikingly, all power
  spectra reveal the presence of enhanced power occurring at ∼3 mHz,
  potentially implying that the excitation of coronal transverse waves
  by p-modes is a global phenomenon.

Title: Model fitting of kink waves in the solar atmosphere: Gaussian
    damping and time-dependence
Authors: Morton, R. J.; Mooroogen, K.
Bibcode: 2016A&A...593A..59M
Altcode: 2016arXiv160705905M
  <BR /> Aims: Observations of the solar atmosphere have shown that
  magnetohydrodynamic waves are ubiquitous throughout. Improvements
  in instrumentation and the techniques used for measurement of the
  waves now enables subtleties of competing theoretical models to
  be compared with the observed waves behaviour. Some studies have
  already begun to undertake this process. However, the techniques
  employed for model comparison have generally been unsuitable and
  can lead to erroneous conclusions about the best model. The aim
  here is to introduce some robust statistical techniques for model
  comparison to the solar waves community, drawing on the experiences
  from other areas of astrophysics. In the process, we also aim to
  investigate the physics of coronal loop oscillations. <BR /> Methods:
  The methodology exploits least-squares fitting to compare models to
  observational data. We demonstrate that the residuals between the
  model and observations contain significant information about the
  ability for the model to describe the observations, and show how
  they can be assessed using various statistical tests. In particular
  we discuss the Kolmogorov-Smirnoff one and two sample tests, as well
  as the runs test. We also highlight the importance of including any
  observational trend line in the model-fitting process. <BR /> Results:
  To demonstrate the methodology, an observation of an oscillating
  coronal loop undergoing standing kink motion is used. The model
  comparison techniques provide evidence that a Gaussian damping profile
  provides a better description of the observed wave attenuation than
  the often used exponential profile. This supports previous analysis
  from Pascoe et al. (2016, A&amp;A, 585, L6). Further, we use the model
  comparison to provide evidence of time-dependent wave properties of
  a kink oscillation, attributing the behaviour to the thermodynamic
  evolution of the local plasma.

Title: Tornados and Transverse Oscillations during Prominence Eruption
Authors: Banerjee, Dipankar; Chandrashekhar, K.; Morton, Richard;
   Pant, Vaibhav; Datta, Ajanta
Bibcode: 2016cosp...41E.141B
Altcode:
  We report and analyse different phases of a prominence eruption. The
  winding-unwinding of two footpoints and a tornado like swirling motion
  is studied. The prominence eruption is observed by the Atmospheric
  Imaging Assembly (AIA) on board the Solar Dynamics Observatory
  (SDO). This prominence eruption is associated with a CME at a
  central principal angle of 340 degree, according to the SOHO/LASCO
  CME catalogue. We can observe the prominence threads and the time
  distance maps reveal that the loop threads are entangled. We also
  study the transverse oscillations in the threads. Swirling motions
  after the eruptions are also quantified and its possible link with
  the CME kinematics is also studied

Title: Nuwt: Northumbria University Wave Tracking (Nuwt) Code
Authors: Morton, Richard J.; Mooroogen, Krishna; McLaughlin, James A.
Bibcode: 2016zndo.....49563M
Altcode:
  This is the first release of the Northumbria University Wave Tracking
  (NUWT) code (in IDL). The code is primarily designed to analyse
  transverse waves along curvilinear features in solar imaging data,
  however, the underlying operations will work on any images. Tutorials
  and videos are included with the release.

Title: On the Properties of Slow MHD Sausage Waves within Small-scale
    Photospheric Magnetic Structures
Authors: Freij, N.; Dorotovič, I.; Morton, R. J.; Ruderman, M. S.;
   Karlovský, V.; Erdélyi, R.
Bibcode: 2016ApJ...817...44F
Altcode: 2015arXiv150908680F
  The presence of magnetoacoustic waves in magnetic structures in the
  solar atmosphere is well-documented. Applying the technique of solar
  magneto-seismology (SMS) allows us to infer the background properties of
  these structures. Here, we aim to identify properties of the observed
  magnetoacoustic waves and study the background properties of magnetic
  structures within the lower solar atmosphere. Using the Dutch Open
  Telescope and Rapid Oscillations in the Solar Atmosphere instruments,
  we captured two series of high-resolution intensity images with short
  cadences of two isolated magnetic pores. Combining wavelet analysis
  and empirical mode decomposition (EMD), we determined characteristic
  periods within the cross-sectional (I.e., area) and intensity time
  series. Then, by applying the theory of linear magnetohydrodynamics
  (MHD), we identified the mode of these oscillations within the MHD
  framework. Several oscillations have been detected within these two
  magnetic pores. Their periods range from 3 to 20 minutes. Combining
  wavelet analysis and EMD enables us to confidently find the phase
  difference between the area and intensity oscillations. From these
  observed features, we concluded that the detected oscillations can
  be classified as slow sausage MHD waves. Furthermore, we determined
  several key properties of these oscillations such as the radial
  velocity perturbation, the magnetic field perturbation, and the
  vertical wavenumber using SMS. The estimated range of the related
  wavenumbers reveals that these oscillations are trapped within these
  magnetic structures. Our results suggest that the detected oscillations
  are standing harmonics, and this allows us to estimate the expansion
  factor of the waveguides by employing SMS. The calculated expansion
  factor ranges from 4 to 12.

Title: Investigating Alfvénic wave propagation in coronal open-field
    regions
Authors: Morton, R. J.; Tomczyk, S.; Pinto, R.
Bibcode: 2015NatCo...6.7813M
Altcode: 2015NatCo...6E7813M
  The physical mechanisms behind accelerating solar and stellar winds are
  a long-standing astrophysical mystery, although recent breakthroughs
  have come from models invoking the turbulent dissipation of Alfvén
  waves. The existence of Alfvén waves far from the Sun has been known
  since the 1970s, and recently the presence of ubiquitous Alfvénic
  waves throughout the solar atmosphere has been confirmed. However,
  the presence of atmospheric Alfvénic waves does not, alone,
  provide sufficient support for wave-based models; the existence of
  counter-propagating Alfvénic waves is crucial for the development of
  turbulence. Here, we demonstrate that counter-propagating Alfvénic
  waves exist in open coronal magnetic fields and reveal key observational
  insights into the details of their generation, reflection in the
  upper atmosphere and outward propagation into the solar wind. The
  results enhance our knowledge of Alfvénic wave propagation in the
  solar atmosphere, providing support and constraints for some of the
  recent Alfvén wave turbulence models.

Title: Multiwavelength Studies of MHD Waves in the Solar
    Chromosphere. An Overview of Recent Results
Authors: Jess, D. B.; Morton, R. J.; Verth, G.; Fedun, V.; Grant,
   S. D. T.; Giagkiozis, I.
Bibcode: 2015SSRv..190..103J
Altcode: 2015arXiv150301769J; 2015SSRv..tmp...14J
  The chromosphere is a thin layer of the solar atmosphere that
  bridges the relatively cool photosphere and the intensely heated
  transition region and corona. Compressible and incompressible waves
  propagating through the chromosphere can supply significant amounts
  of energy to the interface region and corona. In recent years an
  abundance of high-resolution observations from state-of-the-art
  facilities have provided new and exciting ways of disentangling the
  characteristics of oscillatory phenomena propagating through the dynamic
  chromosphere. Coupled with rapid advancements in magnetohydrodynamic
  wave theory, we are now in an ideal position to thoroughly investigate
  the role waves play in supplying energy to sustain chromospheric
  and coronal heating. Here, we review the recent progress made in
  characterising, categorising and interpreting oscillations manifesting
  in the solar chromosphere, with an impetus placed on their intrinsic
  energetics.

Title: Wave Damping Observed in Upwardly Propagating Sausage-mode
    Oscillations Contained within a Magnetic Pore
Authors: Grant, S. D. T.; Jess, D. B.; Moreels, M. G.; Morton, R. J.;
   Christian, D. J.; Giagkiozis, I.; Verth, G.; Fedun, V.; Keys, P. H.;
   Van Doorsselaere, T.; Erdélyi, R.
Bibcode: 2015ApJ...806..132G
Altcode: 2015arXiv150501484G
  We present observational evidence of compressible MHD wave modes
  propagating from the solar photosphere through to the base of the
  transition region in a solar magnetic pore. High cadence images were
  obtained simultaneously across four wavelength bands using the Dunn
  Solar Telescope. Employing Fourier and wavelet techniques, sausage-mode
  oscillations displaying significant power were detected in both
  intensity and area fluctuations. The intensity and area fluctuations
  exhibit a range of periods from 181 to 412 s, with an average period
  ∼290 s, consistent with the global p-mode spectrum. Intensity and
  area oscillations present in adjacent bandpasses were found to be
  out of phase with one another, displaying phase angles of 6.°12,
  5.°82, and 15.°97 between the 4170 Å continuum-G-band, G-band-Na i
  D<SUB>1</SUB>, and Na i D<SUB>1</SUB>-Ca ii K heights, respectively,
  reiterating the presence of upwardly propagating sausage-mode waves. A
  phase relationship of ∼0° between same-bandpass emission and area
  perturbations of the pore best categorizes the waves as belonging to
  the “slow” regime of a dispersion diagram. Theoretical calculations
  reveal that the waves are surface modes, with initial photospheric
  energies in excess of 35,000 W m<SUP>-2</SUP>. The wave energetics
  indicate a substantial decrease in energy with atmospheric height,
  confirming that magnetic pores are able to transport waves that exhibit
  appreciable energy damping, which may release considerable energy into
  the local chromospheric plasma.

Title: First Direct Measurements of Transverse Waves in Solar Polar
    Plumes Using SDO/AIA
Authors: Thurgood, J. O.; Morton, R. J.; McLaughlin, J. A.
Bibcode: 2014ApJ...790L...2T
Altcode: 2014arXiv1406.5348T
  There is intense interest in determining the precise contribution of
  Alfvénic waves propagating along solar structures to the problems
  of coronal heating and solar wind acceleration. Since the launch of
  SDO/AIA, it has been possible to resolve transverse oscillations in
  off-limb solar polar plumes and recently McIntosh et al. concluded
  that such waves are energetic enough to play a role in heating the
  corona and accelerating the fast solar wind. However, this result is
  based on comparisons to Monte Carlo simulations and confirmation via
  direct measurements is still outstanding. Thus, this Letter reports
  on the first direct measurements of transverse wave motions in solar
  polar plumes. Over a four hour period, we measure the transverse
  displacements, periods, and velocity amplitudes of 596 distinct
  oscillations observed in the 171 Å channel of SDO/AIA. We find a
  broad range of non-uniformly distributed parameter values which are
  well described by log-normal distributions with peaks at 234 km,
  121 s, and 8 km s<SUP>-1</SUP>, and mean and standard deviations of
  407 ± 297 km, 173 ± 118 s, and 14 ± 10 km s<SUP>-1</SUP>. Within
  standard deviations, our direct measurements are broadly consistent
  with previous results. However, accounting for the whole of our observed
  non-uniform parameter distribution we calculate an energy flux of 9-24
  W m<SUP>-2</SUP>, which is 4-10 times below the energy requirement for
  solar wind acceleration. Hence, our results indicate that transverse
  magnetohydrodynamic waves as resolved by SDO/AIA cannot be the dominant
  energy source for fast solar wind acceleration in the open-field corona.

Title: High-resolution Observations of Active Region Moss and its
    Dynamics
Authors: Morton, R. J.; McLaughlin, J. A.
Bibcode: 2014ApJ...789..105M
Altcode: 2014arXiv1405.5694M
  The High Resolution Coronal Imager has provided the sharpest view
  of the EUV corona to date. In this paper, we exploit its impressive
  resolving power to provide the first analysis of the fine-scale
  structure of moss in an active region. The data reveal that the moss
  is made up of a collection of fine threads that have widths with a
  mean and standard deviation of 440 ± 190 km (FWHM). The brightest
  moss emission is located at the visible head of the fine-scale
  structure and the fine structure appears to extend into the lower
  solar atmosphere. The emission decreases along the features, implying
  that the lower sections are most likely dominated by cooler transition
  region plasma. These threads appear to be the cool, lower legs of the
  hot loops. In addition, the increased resolution allows for the first
  direct observation of physical displacements of the moss fine structure
  in a direction transverse to its central axis. Some of these transverse
  displacements demonstrate periodic behavior, which we interpret as a
  signature of kink (Alfvénic) waves. Measurements of the properties
  of the transverse motions are made and the wave motions have means
  and standard deviations of 55 ± 37 km for the transverse displacement
  amplitude, 77 ± 33 s for the period, and 4.7 ± 2.5 km s<SUP>-1</SUP>
  for the velocity amplitude. The presence of waves in the transition
  region of hot loops could have important implications for the heating
  of active regions.

Title: Dynamic moss observed with Hi-C
Authors: Alexander, Caroline; Winebarger, Amy R.; Morton, Richard;
   Savage, Sabrina
Bibcode: 2014AAS...22431206A
Altcode:
  The High-resolution Coronal Imager (Hi-C), flown on 11 July 2012,
  has revealed an unprecedented level of detail and substructure within
  the solar corona. Hi-C imaged a large active region (AR11520) with
  0.2-0.3’’ spatial resolution and 5.5s cadence over a 5 minute
  period. An additional dataset with a smaller FOV, the same resolution,
  but with a higher temporal cadence (1s) was also taken during the
  rocket flight. This dataset was centered on a large patch of ‘moss’
  emission that initially seemed to show very little variability. Image
  processing revealed this region to be much more dynamic than first
  thought with numerous bright and dark features observed to appear,
  move and disappear over the 5 minute observation. Moss is thought to
  be emission from the upper transition region component of hot loops so
  studying its dynamics and the relation between the bright/dark features
  and underlying magnetic features is important to tie the interaction of
  the different atmospheric layers together. Hi-C allows us to study the
  coronal emission of the moss at the smallest scales while data from
  SDO/AIA and HMI is used to give information on these structures at
  different heights/temperatures. Using the high temporal and spatial
  resolution of Hi-C the observed moss features were tracked and the
  distribution of displacements, speeds, and sizes were measured. This
  allows us to comment on both the physical processes occurring within
  the dynamic moss and the scales at which these changes are occurring.

Title: Magneto-seismological insights into the penumbral chromosphere
    and evidence for wave damping in spicules
Authors: Morton, R. J.
Bibcode: 2014A&A...566A..90M
Altcode: 2014arXiv1405.3203M
  <BR /> Aims: The observation of propagating magneto-hydrodynamic
  kink waves in magnetic structures and measurement of their
  properties (amplitude, phase speed) can be used to diagnose the
  plasma conditions in the neighbourhood of the magnetic structure
  via magneto-seismology. We aim to reveal properties of the
  chromosphere/transition region above the sunspot penumbra using
  this technique. <BR /> Methods: Hinode SOT observed a sunspot as it
  was crossing over the limb, providing a unique side on view of the
  atmosphere above a sunspot. The presence of large spicule-like jets
  is evident in Ca ii H images. The jets are found to support transverse
  wave motions that displace the central axis of the spicules, which can
  be interpreted as the kink wave. The properties of a specific wave
  event are measured and used to determine the magnetic and density
  stratification along the structure. In addition, we measure the
  width of the spicule and the intensity profile along the structure in
  order to provide a test for the magneto-seismological results. <BR />
  Results: The measurements of the wave properties reveal an initial rapid
  increase in amplitude with height above the solar surface, followed by
  a decrease in amplitude. The magneto-seismological inversions suggests
  this initial increase corresponds to large changes in density and
  magnetic field strength. In addition, we provide the first measurements
  of spicule width with height, which confirm that the spicule under goes
  rapid expansion. The measured rates of expansion show good agreement
  with the results from the magneto-seismology. The observed rapid
  variations in plasma parameters are suggested to be partly due to the
  presence of a gravitational stratified, ambient atmosphere. Combining
  width measurements with phase speed measurements implies the observed
  decrease in wave amplitude at greater heights can be explained by wave
  damping. Hence, we provide the first direct evidence of wave damping
  in chromospheric spicules and the quality factor of the damping is
  found to be significantly smaller than estimated coronal values.

Title: The Generation and Damping of Propagating MHD Kink Waves in
    the Solar Atmosphere
Authors: Morton, R. J.; Verth, G.; Hillier, A.; Erdélyi, R.
Bibcode: 2014ApJ...784...29M
Altcode: 2013arXiv1310.4650M
  The source of the non-thermal energy required for the heating of the
  upper solar atmosphere to temperatures in excess of a million degrees
  and the acceleration of the solar wind to hundreds of kilometers
  per second is still unclear. One such mechanism for providing the
  required energy flux is incompressible torsional Alfvén and kink
  magnetohydrodynamic (MHD) waves, which are magnetically dominated
  waves supported by the Sun's pervasive and complex magnetic field. In
  particular, propagating MHD kink waves have recently been observed
  to be ubiquitous throughout the solar atmosphere, but, until now,
  critical details of the transport of the kink wave energy throughout
  the Sun's atmosphere were lacking. Here, the ubiquity of the
  waves is exploited for statistical studies in the highly dynamic
  solar chromosphere. This large-scale investigation allows for the
  determination of the chromospheric kink wave velocity power spectra, a
  missing link necessary for determining the energy transport between the
  photosphere and corona. Crucially, the power spectra contain evidence
  for horizontal photospheric motions being an important mechanism for
  kink wave generation in the quiescent Sun. In addition, a comparison
  with measured coronal power spectra is provided for the first time,
  revealing frequency-dependent transmission profiles, suggesting that
  there is enhanced damping of kink waves in the lower corona.

Title: The dynamical behaviour of a jet in an on-disk coronal hole
    observed with AIA/SDO
Authors: Chandrashekhar, K.; Morton, R. J.; Banerjee, D.; Gupta, G. R.
Bibcode: 2014A&A...562A..98C
Altcode: 2013arXiv1310.7853C
  <BR /> Aims: Extreme ultraviolet (EUV) jets situated in coronal holes
  are thought to play an important role in supplying heated material
  to the corona and solar wind. The multi-wavelength capabilities and
  high signal-to-noise ratio of detectors on board the Solar Dynamic
  Observatory (SDO) allow for detailed study of these jets' evolution. We
  aim to exploit SDO's capabilities to reveal information on the jet
  dynamics and to obtain estimates for plasma properties associated with
  the jets. <BR /> Methods: We studied the dynamics of an EUV jet with
  SDO at a coronal hole boundary. The details of the jet evolution are
  discussed and measurements of the jet's parameters, e.g. length, width,
  life time, and outward speed, are obtained. Furthermore, automated
  emission measure analysis is exploited to determine estimates for
  the temperature and density of the jet. A propagating transverse
  wave supported by the jet spire is also observed. Measurements of
  the wave properties are exploited for magneto-seismology and are
  used in conjunction with the emission measure results to estimate
  the magnetic field strength of the jet. <BR /> Results: We present
  a detailed description of the jet's evolution, with new evidence
  of plasma flows, prior to the jet's initiation, along the loops
  at the base of the jet and also find further evidence that flows
  along the jet spire consist of multiple, quasi-periodic small-scale
  plasma ejection events. In addition, spectroscopic analysis reveal
  that the jet has temperatures of log 5.89 ± 0.08 K and electron
  densities of log 8.75 ± 0.05 cm<SUP>-3</SUP>. Measured properties
  of the transverse wave provide evidence that a strong damping of
  the wave occurs as it propagates along the jet spire with speeds of
  ~110 km s<SUP>-1</SUP>. The magneto-seismological inversion of the
  wave parameters provides values of B = 1.21 ± 0.2 G along the jet
  spire, which is in line with previous estimates for open fields in
  coronal holes. <P />Movies are available in electronic form at <A
  href="http://www.aanda.org/10.1051/0004-6361/201322408/olm">http://www.aanda.org</A>

Title: Magneto-seismological insights into the penumbral chromosphere
    and evidence for wave damping in chromospheric wave-guides
Authors: Morton, Richard
Bibcode: 2014cosp...40E2180M
Altcode:
  The observation of propagating magneto-hydrodynamic kink waves in
  magnetic structures and measurement of their properties (amplitude,
  phase speed) can be used to diagnose the plasma conditions in the
  neighbourhood of the magnetic structure via magneto-seismology. Hinode
  SOT observed a sunspot as it was crossing over the limb, providing a
  unique side on view of the Sunspot atmosphere. The presence of large
  spicule-like jets is evident in Ca II H images and they are found to
  support transverse (kink) motions. The properties of a specific wave
  event are measured and used to determine the magnetic and density
  stratification along the structure. In addition, we can measure the
  width of the spicule and the intensity profile along the structure
  in order to provide a test for the magneto-seismological results. I
  will discuss the techniques behind the measurements and what the
  seismological results can reveal about the chromosphere above a
  sunspot. These results are contrasted to the direct measurements of
  the spicule properties and a good agreement is found between measured
  and seismological-ly inferred quantities. Perhaps most importantly, we
  demonstrate that a combination of seismological and measured properties
  implies that an observed decrease in wave amplitude at greater heights
  is due to wave damping. Hence, the first evidence of wave damping in
  chromospheric wave-guides is provided. The quality factor of the damping
  is found to be significantly smaller than estimated coronal values.

Title: Transverse Oscillations observed in a Jet and coronal
    seismology
Authors: Banerjee, Dipankar; Chandrashekhar, K.; Morton, Richard
Bibcode: 2014cosp...40E.204B
Altcode:
  Extreme Ultra Violet (EUV) jets situated in coronal holes are thought to
  play an important role in supplying heated material to the corona and
  solar wind. The multi-wavelength capabilities and high signal-to-noise
  ratio of detectors on-board Solar Dynamic Observatory (SDO) allows for
  detailed study of these jet’s evolution. We aim to exploit SDO’s
  capabilities to reveal information on the jet dynamics and to obtain
  estimates for plasma properties associated with the jet. We studied
  the dynamics an EUV jet with SDO at a coronal hole boundary. The
  details of the jet evolution are discussed and measurements of the
  jet’s parameters, e.g. length, width, life time, and outward speed,
  are obtained. Furthermore, automated emission measure analysis is
  exploited to determine estimates for the temperature and density of
  the jet. A propagating transverse wave supported by the jet spire is
  also observed. Measurement of the wave properties are exploited for
  magneto-seismology and are used in conjunction with the emission measure
  results to estimate the magnetic field strength of the jet. We present
  a detailed description of the jet’s evolution, with new evidence of
  plasma flows, prior to the jet’s initiation, along the loops at the
  base of the jet and also find further evidence that flows along the jet
  spire consist of multiple, quasi-periodic small scale plasma ejection
  events. In addition, spectroscopic analysis reveal that the jet has
  temperatures of log 5.89 ±0.08 K and electron densities of log 8.75
  ± 0.05 cm(-3) . Measured properties of the transverse wave provide
  evidence that a strong damping of the wave occurs as it propagates
  along the jet spire with speeds of 110 km/s. The magneto-seismological
  inversion of the wave parameters provides values of B = 1.21 ±0.2
  G along the jet spire, which is in line with previous estimates for
  open fields in coronal holes.

Title: High-resolution observations of active region moss and its
    dynamics
Authors: Morton, Richard; McLaughlin, James
Bibcode: 2014cosp...40E2181M
Altcode:
  The High resolution Coronal Imager (Hi-C) has provided the sharpest
  view of the EUV corona to date. I will present results that exploit
  its impressive resolving power to provide the first analysis of the
  fine-scale structure of moss in an active region. The data reveal
  that the moss is made up of a collection of fine threads that have
  widths ranging between 400-1000 km. These fine-scale structures are
  connected to the bright moss and appear to extend into the lower solar
  atmosphere. The emission decreases along the features implying the
  lower sections are most likely dominated by cooler transition region
  plasma. These threads appear to be the cool, lower legs of the hot
  loops. The increased resolution also allows for the first direct
  observation of physical displacements of the moss fine-structure in
  a direction transverse to its central axis. Some of these transverse
  displacements demonstrate periodic behaviour, which we interpret as
  a signature of kink (Alfvénic) waves. The presence of waves in the
  transition region of hot loops could have important implications for
  the heating of active regions.

Title: Characteristics of Transverse Waves in Chromospheric Mottles
Authors: Kuridze, D.; Verth, G.; Mathioudakis, M.; Erdélyi, R.;
   Jess, D. B.; Morton, R. J.; Christian, D. J.; Keenan, F. P.
Bibcode: 2013ApJ...779...82K
Altcode: 2013arXiv1310.3628K
  Using data obtained by the high temporal and spatial resolution
  Rapid Oscillations in the Solar Atmosphere instrument on the Dunn
  Solar Telescope, we investigate at an unprecedented level of detail
  transverse oscillations in chromospheric fine structures near the solar
  disk center. The oscillations are interpreted in terms of propagating
  and standing magnetohydrodynamic kink waves. Wave characteristics
  including the maximum transverse velocity amplitude and the phase
  speed are measured as a function of distance along the structure's
  length. Solar magnetoseismology is applied to these measured parameters
  to obtain diagnostic information on key plasma parameters (e.g.,
  magnetic field, density, temperature, flow speed) of these localized
  waveguides. The magnetic field strength of the mottle along the ~2 Mm
  length is found to decrease by a factor of 12, while the local plasma
  density scale height is ~280 ± 80 km.

Title: A Statistical Study of Transverse Oscillations in a Quiescent
    Prominence
Authors: Hillier, A.; Morton, R. J.; Erdélyi, R.
Bibcode: 2013ApJ...779L..16H
Altcode: 2013arXiv1310.8009H
  The launch of the Hinode satellite has allowed for seeing-free
  observations at high-resolution and high-cadence making it well suited
  to study the dynamics of quiescent prominences. In recent years it
  has become clear that quiescent prominences support small-amplitude
  transverse oscillations, however, sample sizes are usually too small
  for general conclusions to be drawn. We remedy this by providing a
  statistical study of transverse oscillations in vertical prominence
  threads. Over a 4 hr period of observations it was possible to
  measure the properties of 3436 waves, finding periods from 50 to
  6000 s with typical velocity amplitudes ranging between 0.2 and 23
  km s<SUP>-1</SUP>. The large number of observed waves allows the
  determination of the frequency dependence of the wave properties and
  derivation of the velocity power spectrum for the transverse waves. For
  frequencies less than 7 mHz, the frequency dependence of the velocity
  power is consistent with the velocity power spectra generated from
  observations of the horizontal motions of magnetic elements in the
  photosphere, suggesting that the prominence transverse waves are
  driven by photospheric motions. However, at higher frequencies the two
  distributions significantly diverge, with relatively more power found
  at higher frequencies in the prominence oscillations. These results
  highlight that waves over a large frequency range are ubiquitous in
  prominences, and that a significant amount of the wave energy is found
  at higher frequency.

Title: Hi-C and AIA observations of transverse magnetohydrodynamic
    waves in active regions (Corrigendum)
Authors: Morton, R. J.; McLaughlin, J. A.
Bibcode: 2013A&A...556C...1M
Altcode:
  No abstract at ADS

Title: Hi-C and AIA observations of transverse magnetohydrodynamic
    waves in active regions
Authors: Morton, R. J.; McLaughlin, J. A.
Bibcode: 2013A&A...553L..10M
Altcode: 2013arXiv1305.0140M
  The recent launch of the High resolution Coronal imager (Hi-C)
  provided a unique opportunity of studying the EUV corona with
  unprecedented spatial resolution. We utilize these observations
  to investigate the properties of low-frequency (50-200 s) active
  region transverse waves, whose omnipresence had been suggested
  previously. The five-fold improvement in spatial resolution over
  SDO/AIA reveals coronal loops with widths 150-310 km and that these
  loops support transverse waves with displacement amplitudes &lt;50
  km. However, the results suggest that wave activity in the coronal
  loops is of low energy, with typical velocity amplitudes &lt;3 km
  s<SUP>-1</SUP>. An extended time-series of SDO data suggests that
  low-energy wave behaviour is typical of the coronal structures both
  before and after the Hi-C observations. <P />Appendix A and five
  movies associated to Figs. A.2-A.6 are available in electronic form
  at <A href="http://www.aanda.org">http://www.aanda.org</A>

Title: Evidence for the Photospheric Excitation of Incompressible
    Chromospheric Waves
Authors: Morton, R. J.; Verth, G.; Fedun, V.; Shelyag, S.; Erdélyi, R.
Bibcode: 2013ApJ...768...17M
Altcode: 2013arXiv1303.2356M
  Observing the excitation mechanisms of incompressible transverse
  waves is vital for determining how energy propagates through the lower
  solar atmosphere. We aim to show the connection between convectively
  driven photospheric flows and incompressible chromospheric waves. The
  observations presented here show the propagation of incompressible
  motion through the quiet lower solar atmosphere, from the photosphere
  to the chromosphere. We determine photospheric flow vectors to search
  for signatures of vortex motion and compare results to photospheric
  flows present in convective simulations. Further, we search for the
  chromospheric response to vortex motions. Evidence is presented that
  suggests incompressible waves can be excited by the vortex motions of a
  strong magnetic flux concentration in the photosphere. A chromospheric
  counterpart to the photospheric vortex motion is also observed,
  presenting itself as a quasi-periodic torsional motion. Fine-scale,
  fibril structures that emanate from the chromospheric counterpart
  support transverse waves that are driven by the observed torsional
  motion. A new technique for obtaining details of transverse waves from
  time-distance diagrams is presented and the properties of transverse
  waves (e.g., amplitudes and periods) excited by the chromospheric
  torsional motion are measured.

Title: SDO/AIA observations of periodic and quasi-periodic phenomenon
    associated with an EUV jet
Authors: Morton, Richard; Verth, Gary; Erdelyi, Robertus; Srivastava,
   Abhi
Bibcode: 2013EGUGA..15...52M
Altcode:
  It has long been advocated that explosive magnetic activity is
  responsible for the mass-balance in the solar atmosphere, supplying
  the corona and the solar wind with heated plasma. The explosive
  events are thought to be the result of emerging bi-polar (EB) regions
  reconnecting with pre-existing, open fields, with the size of the EB's
  (i.e., granular, super-granular) being related to size of the resulting
  feature (i.e., spicules, EUV/X-ray jets). Recent evidence has suggested
  a deeper relationship between spicules and EUV jets (Sterling et al.,
  2010). We present here observations of a EUV jet observed with SDO/AIA
  close to a southern coronal hole. The jet can be considered as a
  'Blowout jet' (using the terminology of Moore et al., 2010), launching
  vast amounts of chromospheric plasma into the atmosphere along with
  hotter material. The hotter part of the jet appears to be composed
  of multiple, (quasi-)periodic ejections that individually resemble
  fast moving (&gt;100 km/s) spicules. The multiple ejections appear
  crucial for distributing the hotter material high into the corona,
  possibly suggesting that larger EUV/X-ray are composed of many smaller
  spicule-like events. Although the event is close to the limb, evidence
  for reconnection at the chromospheric level is provided. Further,
  evidence for helicity (or torsional motion) and the presence of slow and
  fast Magnetohydrodynamic waves is given, with the wave mode excitation
  likely due to the reconnection process. Exploiting the observed wave
  motion, we also use magneto-seismological techniques to determine local
  plasma parameters with sub-resolution accuracy along one of the jets
  unique features.

Title: Observations of ubiquitous compressive waves in the Sun's
    chromosphere
Authors: Morton, Richard J.; Verth, Gary; Jess, David B.; Kuridze,
   David; Ruderman, Michael S.; Mathioudakis, Mihalis; Erdélyi, Robertus
Bibcode: 2012NatCo...3.1315M
Altcode: 2012NatCo...3E1315M; 2013arXiv1306.4124M
  The details of the mechanism(s) responsible for the observed
  heating and dynamics of the solar atmosphere still remain a
  mystery. Magnetohydrodynamic waves are thought to have a vital role
  in this process. Although it has been shown that incompressible
  waves are ubiquitous in off-limb solar atmospheric observations,
  their energy cannot be readily dissipated. Here we provide, for the
  first time, on-disk observation and identification of concurrent
  magnetohydrodynamic wave modes, both compressible and incompressible,
  in the solar chromosphere. The observed ubiquity and estimated energy
  flux associated with the detected magnetohydrodynamic waves suggest
  the chromosphere is a vast reservoir of wave energy with the potential
  to meet chromospheric and coronal heating requirements. We are also
  able to propose an upper bound on the flux of the observed wave energy
  that is able to reach the corona based on observational constraints,
  which has important implications for the suggested mechanism(s) for
  quiescent coronal heating.

Title: Thin glass shell oriented to wide field x-ray telescope
Authors: Civitani, M. M.; Citterio, O.; Campana, S.; Conconi, P.;
   Mattaini, E.; Pareschi, G.; Tagliaferri, G.; Parodi, G.; Burwitz, V.;
   Hartner, G. D.; Arnold, J.; Schuler, S.; Combrinck, H.; Freeman, R.;
   Morton, R.; Simpson, P.; Walker, D.
Bibcode: 2012SPIE.8443E..0QC
Altcode:
  The next generation wide-field X-ray telescope (WFXT), to be implemented
  beyond eRosita and proposed within the NASA RFI call 2011, requires
  an angular resolution of less than 10 arcsec (with goal of 5”)
  constant across a wide field of view (1 deg<SUP>2</SUP>). To achieve
  this requirement the design is based on nested modified grazing
  incidence Wolter-I mirrors with polynomial profiles. Our goals in
  terms of mass and stiffness can be meet with the use of fused silica
  glass, a wellknown material with good thermo-mechanical properties and
  polishability characteristics, together with an innovative polishing
  approach. Here we present the X-ray calibration results obtained for
  a prototypal shell tested in fullillumination mode at the Panter/MPE
  facility.

Title: Observations of Magneto-acoustic Waves above the Intensity
    Enhanced Quiet Sun Regions from Hinode/SOT
Authors: Srivastava, Abhishek K.; Von Fay-Siebenburgen Erdélyi,
   Robert; Fedun, Viktor; Ravindra, B.; Morton, R. J.
Bibcode: 2012cosp...39.1883S
Altcode: 2012cosp.meet.1883S
  No abstract at ADS

Title: Chromospheric jets around the edges of sunspots
Authors: Morton, R. J.
Bibcode: 2012A&A...543A...6M
Altcode: 2012arXiv1205.2307M
  <BR /> Aims: Evidence is beginning to be put forward that
  demonstrates the role of the chromosphere in supplying energy and
  mass to the corona. We aim to assess the role of chromospheric jets
  in active region dynamics. <BR /> Methods: Using a combination of
  the Hinode/SOT Ca II H and TRACE 1550 Å and 1600 Å filters we
  examine chromospheric jets situated at the edge of a sunspot. <BR />
  Results: Analysis reveals a near continuous series of jets, that raise
  chromospheric material into the low corona above a sunspot. The jets
  have average rise speeds of 30 km s<SUP>-1</SUP> and a range of 10-100
  km s<SUP>-1</SUP>. Enhanced emission observed at the jets leading
  edge suggests the formation of a shock front. Increased emission in
  TRACE bandpasses above the sunspot and the disappearance of the jets
  from the Ca II filter suggests that some of the chromospheric jet
  material is at least heated to ~0.1 MK. The evidence suggests that
  the jets could be a source of steady, low-level heating for active
  region features. <P />Movie is available in electronic form at <A
  href="http://www.aanda.org">http://www.aanda.org</A>

Title: Observations of quasi-periodic phenomena associated with a
    large blowout solar jet
Authors: Morton, R. J.; Srivastava, A. K.; Erdélyi, R.
Bibcode: 2012A&A...542A..70M
Altcode: 2012arXiv1204.5033M
  <BR /> Aims: A variety of periodic phenomena have been observed in
  conjunction with large solar jets. We aim to find further evidence for
  (quasi-)periodic behaviour in solar jets and determine what the periodic
  behaviour can tell us about the excitation mechanism and formation
  process of the large solar jet. <BR /> Methods: Using the 304 Å
  (He-II), 171 Å (Fe IX), 193 Å (Fe XII/XXIV) and 131 Å (Fe VIII/XXI)
  filters onboard the Solar Dynamic Observatory (SDO) Atmospheric
  Imaging Assembly (AIA), we investigate the intensity oscillations
  associated with a solar jet. <BR /> Results: Evidence is provided for
  multiple magnetic reconnection events occurring between a pre-twisted,
  closed field and open field lines. Components of the jet are seen
  in multiple SDO/AIA filters covering a wide range of temperatures,
  suggesting the jet can be classified as a blowout jet. Two bright,
  elongated features are observed to be co-spatial with the large jet,
  appearing at the jet's footpoints. Investigation of these features
  reveal they are defined by multiple plasma ejections. The ejecta
  display (quasi-)periodic behaviour on timescales of 50 s and have
  rise velocities of 40-150 km s<SUP>-1</SUP> along the open field
  lines. Due to the suggestion that the large jet is reconnection-driven
  and the observed properties of the ejecta, we further propose that these
  ejecta events are similar to type-II spicules. The bright features also
  display (quasi)-periodic intensity perturbations on the timescale of
  300 s. Possible explanations for the existence of the (quasi-)periodic
  perturbations in terms of jet dynamics and the response of the
  transition region are discussed. <P />Movies are available in electronic
  form at <A href="http://www.aanda.org">http://www.aanda.org</A>

Title: Transverse Oscillations in Chromospheric Mottles
Authors: Kuridze, D.; Morton, R. J.; Erdélyi, R.; Dorrian, G. D.;
   Mathioudakis, M.; Jess, D. B.; Keenan, F. P.
Bibcode: 2012ApJ...750...51K
Altcode: 2012arXiv1202.5697K
  A number of recent investigations have revealed that transverse
  waves are ubiquitous in the solar chromosphere. The vast majority
  of these have been reported in limb spicules and active region
  fibrils. We investigate long-lived, quiet-Sun, on-disk features such as
  chromospheric mottles (jet-like features located at the boundaries of
  supergranular cells) and their transverse motions. The observations
  were obtained with the Rapid Oscillations in the Solar Atmosphere
  instrument at the Dunn Solar Telescope. The data set is comprised
  of simultaneous imaging in the Hα core, Ca II K, and G band of an
  on-disk quiet-Sun region. Time-distance techniques are used to study
  the characteristics of the transverse oscillations. We detect over
  40 transverse oscillations in both bright and dark mottles, with
  periods ranging from 70 to 280 s, with the most frequent occurrence
  at ~165 s. The velocity amplitudes and transverse displacements
  exhibit characteristics similar to limb spicules. Neighboring mottles
  oscillating in-phase are also observed. The transverse oscillations
  of individual mottles are interpreted in terms of magnetohydrodynamic
  kink waves. Their estimated periods and damping times are consistent
  with phase mixing and resonant mode conversion.

Title: Determination of Sub-resolution Structure of a Jet by Solar
    Magnetoseismology
Authors: Morton, R. J.; Verth, G.; McLaughlin, J. A.; Erdélyi, R.
Bibcode: 2012ApJ...744....5M
Altcode: 2011arXiv1109.4851M
  A thin dark thread is observed in a UV/EUV solar jet in the 171 Å,
  193 Å, and 211 Å, and partially in 304 Å. The dark thread appears
  to originate in the chromosphere but its temperature does not appear
  to lie within the passbands of the Atmospheric Imaging Assembly
  onboard the Solar Dynamics Observatory. We therefore implement solar
  magnetoseismology to estimate the plasma parameters of the dark
  thread. A propagating kink (transverse) wave is observed to travel
  along the dark thread. The wave is tracked over a range of ~7000 km
  by placing multiple slits along the axis of the dark thread. The phase
  speed and amplitude of the wave are estimated and magnetoseismological
  theory is employed to determine the plasma parameters. We are able
  to estimate the plasma temperature, density gradient, magnetic field
  gradient, and sub-resolution expansion of the dark thread. The dark
  thread is found to be cool, T &lt;~ 3 × 10<SUP>4</SUP>, with both
  strong density and magnetic field gradients. The expansion of the flux
  tube along its length is ~300-400 km.

Title: Torsional Alfvén waves: magneto-seismology in static and
    dynamic coronal plasmas
Authors: Morton, R. J.; Ruderman, M. S.; Erdélyi, R.
Bibcode: 2011A&A...534A..27M
Altcode:
  <BR /> Aims: We study the properties of torsional Alfvén waves in
  coronal loops so that they may be exploited for coronal seismological
  applications. <BR /> Methods: The governing equation is obtained
  for standing torsional Alfvén waves of a dynamic, gravitationally
  stratified plasma. The footpoints are assumed to obey line-tying
  conditions necessary for standing oscillations. Solutions are found
  in a number of different but typical scenarios to demonstrate the
  possibilities for both temporal and spatial magneto-seismology
  exploitation of waveguides with the standing torsional Alfvén
  oscillations. <BR /> Results: It is found that the frequency of the
  standing Alfvén oscillation increases as the stratification of the
  plasma increases. The ratio of the periods of the fundamental modeand
  the first overtone is also found to change as the stratification of the
  plasma increases. Further, the eigenfunctions of the higher overtones
  of the standing oscillations are found to experience a shift of their
  anti-nodes. The influence of a dynamic plasma on the amplitudes of the
  mode is also investigated. The amplitude of the torsional Alfvén mode
  is found to increase as the plasma within the coronal loop experiences
  cooling.

Title: Progress on precise grinding and polishing of thin glass
    monolithic shell (towards WFXT)
Authors: Citterio, O.; Civitani, M. M.; Arnold, J.; Campana, S.;
   Combrinck, H.; Conconi, P.; Cotroneo, V.; Freeman, R.; Mattaini,
   E.; Morton, R.; Motta, G.; Pareschi, G.; Parodi, G.; Proserpio, L.;
   Schuler, S.; Simpson, P.; Tagliaferri, G.; Walker, D.
Bibcode: 2011SPIE.8147E..14C
Altcode: 2011SPIE.8147E..37C
  The next generation wide-field X-ray telescope (WFXT) will require an
  angular resolution of ~5-10 arcsec almost constant across a wide field
  of view (~1 deg<SUP>2</SUP> diameter). To achieve this goal, the design
  of the optical system has to be based on mirrors characterized by short
  length and polynomial profiles, as well as focal plane curvature and
  plate scale corrections. These concepts guarantee an improved angular
  resolution at large off-axis angle with respect to the normally
  used Wolter-I configuration. These telescopes are therefore optimal
  for survey purposes. A significant increase of effective area and
  grasp with respect to previous missions must also be achieved. This
  is possible with high precision but at the same time thin (2-3 mm
  thickness for mirror diameters of 30-110 cm) glass mirror shells. To
  achieve the goal of 5 arcsec and improve further the technology, we are
  considering different materials. Fused silica, a well-known material
  with good thermo-mechanical and polishability characteristics provide
  the best choice. To bring the mirror shells to the needed accuracy,
  we are adopting a deterministic direct polishing method (already used
  for past missions as Einstein, Rosat, Chandra). The technological
  challenge now is to apply it for almost ten times thinner shells.

Title: Damping of Longitudinal Magneto-Acoustic Oscillations in
    Slowly Varying Coronal Plasma
Authors: Erdélyi, R.; Al-Ghafri, K. S.; Morton, R. J.
Bibcode: 2011SoPh..272...73E
Altcode: 2010arXiv1011.2617E; 2011SoPh..tmp..314E; 2011SoPh..tmp..184E;
   2011SoPh..tmp..253E; 2011SoPh..tmp..289E
  We investigate the propagation of MHD waves in a magnetised plasma
  in a weakly stratified atmosphere, representative of hot coronal
  loops. In most earlier studies, a time-independent equilibrium was
  considered. Here we abandon this restriction and allow the equilibrium
  to develop as a function of time. In particular, the background plasma
  is assumed to be cooling due to thermal conduction. The cooling is
  assumed to occur on a time scale greater than the characteristic travel
  times of the perturbations. We investigate the influence of cooling of
  the background plasma on the properties of magneto-acoustic waves. The
  MHD equations are reduced to a 1D system modelling magneto-acoustic
  modes propagating along a dynamically cooling coronal loop. A
  time-dependent dispersion relation that describes the propagation of
  the magneto-acoustic waves is derived using the WKB theory. An analytic
  solution for the time-dependent amplitude of waves is obtained, and
  the method of characteristics is used to find an approximate analytical
  solution. Numerical calculations of the analytically derived solutions
  are obtained to give further insight into the behaviour of the MHD waves
  in a system with a variable, time-dependent background. The results show
  that there is a strong damping of MHD waves and the damping also appears
  to be independent of the position along the loop. Studies of MHD wave
  behaviour in a time-dependent backgrounds seem to be a fundamental
  and very important next step in the development of MHD wave theory
  that is applicable to a wide range of situations in solar physics.

Title: Kink and fluting modes of stratified coronal magnetic loops
    with elliptical cross-sections
Authors: Morton, R. J.; Ruderman, M. S.
Bibcode: 2011A&A...527A..53M
Altcode: 2010arXiv1011.2377M
  <BR /> Aims: We study kink and fluting oscillations of a straight
  magnetic tube with an elliptic cross-section and density varying
  along the tube. <BR /> Methods: The governing equations for kink and
  fluting modes in the thin tube approximation are derived. We found
  that there are two kink modes, polarised along the semimajor and
  semiminor axes of the elliptic cross-section. We have shown that the
  ratio of frequencies of the first overtone and fundamental mode is the
  same for both kink modes and independent of the ratio of the ellipse
  axes. <BR /> Results: On the basis of this result we concluded that the
  estimates of the atmospheric scale height obtained using simultaneous
  observations of the fundamental mode and first overtone of the coronal
  loop kink oscillations are independent of the ellipticity of the loop
  cross-section.

Title: Observations of Sausage Modes in Magnetic Pores
Authors: Morton, R. J.; Erdélyi, R.; Jess, D. B.; Mathioudakis, M.
Bibcode: 2011ApJ...729L..18M
Altcode: 2010arXiv1011.2375M
  We present here evidence for the observation of the magnetohydrodynamic
  (MHD) sausage modes in magnetic pores in the solar photosphere. Further
  evidence for the omnipresent nature of acoustic global modes is also
  found. The empirical decomposition method of wave analysis is used to
  identify the oscillations detected through a 4170 Å "blue continuum"
  filter observed with the Rapid Oscillations in the Solar Atmosphere
  (ROSA) instrument. Out of phase, periodic behavior in pore size and
  intensity is used as an indicator of the presence of magnetoacoustic
  sausage oscillations. Multiple signatures of the magnetoacoustic
  sausage mode are found in a number of pores. The periods range from
  as short as 30 s up to 450 s. A number of the magnetoacoustic sausage
  mode oscillations found have periods of 3 and 5 minutes, similar to
  the acoustic global modes of the solar interior. It is proposed that
  these global oscillations could be the driver of the sausage-type
  magnetoacoustic MHD wave modes in pores.

Title: Application of the theory of damping of kink oscillations by
    radiative cooling of coronal loop plasma
Authors: Morton, R. J.; Erdélyi, R.
Bibcode: 2010A&A...519A..43M
Altcode:
  <BR /> Aims: We present here a first comparative study between the
  observed damping of numerous fast kink oscillations and the theoretical
  model of their damping due to the cooling of coronal loops. The theory
  of damping of kink oscillations due to radiation of the solar plasma
  with a temporally varying background is applied here to all known
  cases of coronal kink oscillations. <BR /> Methods: A recent dynamic
  model of cooling coronal loops predicts that transverse oscillations of
  such loops could be significantly damped due to the radiative cooling
  process (Morton &amp; Erdélyi 2009, ApJ, 707, 750). The cooling of the
  loop plasma also has the consequence that the kink oscillation has a
  time-dependent frequency. The theory is applied to a relatively large
  number of known and reported examples of TRACE observations of damped
  kink oscillations. <BR /> Results: We find that, for cooling timescales
  that are typical of EUV loops (500-2000 s), the observed damping of
  the transversal (i.e. kink) oscillations can be accounted for almost
  entirely by the cooling process in half of the examples. No other
  dissipative mechanism(s) seems to be needed to model the damping. In
  the remaining other examples, the cooling process does not appear to
  be able to account fully for the observed damping, though could still
  have a significant influence on the damping. In these cases another
  mechanism(s), e.g. resonant absorption, may be additionally required
  to account for the complete decay of oscillations. Also, we show that
  because of the dynamic nature of the background plasma, allowing for
  a time-dependent frequency provides a better fit profile for the data
  points of observations than a fit profile with a constant frequency,
  opening novel avenues for solar magneto-seismology.

Title: Design and development of thin quartz glass WFXT polynomial
    mirror shells by direct polishing
Authors: Proserpio, L.; Campana, S.; Citterio, O.; Civitani, M.;
   Combrinck, H.; Conconi, P.; Cotroneo, V.; Freeman, R.; Langstrof,
   P.; Mattaini, E.; Morton, R.; Oberle, B.; Pareschi, G.; Parodi, G.;
   Pels, C.; Schenk, C.; Stock, R.; Tagliaferri, G.
Bibcode: 2010SPIE.7732E..0DP
Altcode: 2010SPIE.7732E..10P
  The Wide Field X-ray Telescope (WFXT) is a medium class mission for
  X-ray surveys of the sky with an unprecedented area and sensitivity. In
  order to meet the effective area requirement, the design of the
  optical system is based on very thin mirror shells, with thicknesses
  in the 1-2 mm range. In order to get the desired angular resolution
  (10 arcsec requirement, 5 arcsec goal) across the entire 1x1 degree FOV
  (Field Of View), the design of the optical system is based on nested
  modified grazing incidence Wolter-I mirrors realized with polynomial
  profiles, focal plane curvature and plate scale corrections. This design
  guarantees an increased angular resolution at large off-axis angle with
  respect to the normally used Wolter I configuration, making WFXT ideal
  for survey purposes. The WFXT X-ray Telescope Assembly is composed by
  three identical mirror modules of 78 nested shells each, with diameter
  up to 1.1 m. The epoxy replication process with SiC shells has already
  been proved to be a valuable technology to meet the angular resolution
  requirement of 10 arcsec. To further mature the telescope manufacturing
  technology and to achieve the goal of 5 arcsec, a deterministic direct
  polishing method is under investigation. The direct polishing method
  has already been used for past missions (as Einstein, Rosat, Chandra):
  the technological challenge now is to apply it for almost ten times
  thinner shells. Under investigation is quartz glass (fused silica),
  a well-known material with good thermo-mechanical and polishability
  characteristics that could meet our goal in terms of mass and stiffness,
  with significant cost and time saving with respect to SiC. Our approach
  is based on two main steps: first quartz glass tubes available on the
  market are grinded to conical profiles, and second the obtained shells
  are polished to the required polynomial profiles by CNC (Computer
  Numerical Control) polishing machine. In this paper, the first results
  of the direct grinding and polishing of prototypes shells made by quartz
  glass with low thickness, representative of the WFXT optical design,
  are presented.

Title: Propagating magneto-hydrodynamic waves in a cooling homogenous
    coronal plasma
Authors: Morton, R. J.; Hood, A. W.; Erdélyi, R.
Bibcode: 2010A&A...512A..23M
Altcode:
  <BR /> Aims: We present an investigation into how the cooling of the
  background plasma influences the propagation of slow and fast MHD
  wave modes supported by an unbounded, homogenous plasma. Previous
  investigations have suggested that the cooling of the plasma and a
  reduction in density could lead to the damping of fast magneto-acoustic
  oscillations. We aim to investigate whether cooling of the background
  plasma at a constant density may be responsible for the damping of
  slow and fast modes. <BR /> Methods: The plasma is assumed homogeneous
  and the background temperature (pressure) is decreasing with time. The
  temperature change is assumed to be due to optically thin radiation. A
  special case of the radiative function is chosen to allow an analytical
  assessment of the effects of cooling on magneto-acoustic MHD modes
  and ensures the temperature evolution of the background plasma
  due to this radiation also matches the observed cooling profile of
  coronal loops. <BR /> Results: A time-dependent dispersion relation
  is obtained on the slow timescale of cooling and full time-dependent
  solutions are found. Leading order equations for the amplitude of the
  waves are obtained and solved analytically for the slow and fast MHD
  modes. The cooling of the plasma is found to cause the frequency of the
  magneto-acoustic modes to decrease with time. The slow modes are found
  to experience a greater change in frequency than the fast modes. More
  importantly, the radiative losses also provide a significant damping
  of the slow mode and a small damping of the component of the fast mode
  perpendicular to the magnetic field. The damping of the slow mode is
  found to be strong within typical lifetimes of oscillations observed in
  coronal structures. Cooling could have important consequences and needs
  to be assessed when trying to determine what mechanism is responsible
  for the observed damping of coronal oscillations.

Title: Transverse Oscillations of a Cooling Coronal Loop
Authors: Morton, R. J.; Erdélyi, R.
Bibcode: 2009ApJ...707..750M
Altcode:
  Here we present an investigation into how cooling of the plasma
  influences the oscillation properties (e.g., eigenfunctions and
  eigenfrequencies) of transverse (i.e., kink) magnetohydrodynamic
  (MHD) waves in a compressible magnetic flux tube embedded in a
  gravitationally stratified and uniformly magnetized atmosphere. The
  cooling is introduced via a temperature-dependent density profile. A
  time-dependent governing equation is derived and an approximate
  zeroth-order solution is then obtained. From this the influence of
  cooling on the behavior of the eigenfrequencies and eigenfunctions
  of the transverse MHD waves is determined for representative
  cooling timescales. It is shown analytically, as the loop cools,
  how the amplitude of the perturbations is found to decrease as time
  increases. For cooling timescales of 900-2000 s (as observed in
  typical EUV loops), it is shown that the cooling has important and
  relevant influence on the damping times of loop oscillations. Next,
  the theory is put to the test. The damping due to cooling is fitted
  to a representative observation of standing kink oscillation of EUV
  loops. It is also shown with an explicit approximate analytical form,
  how the period of the fundamental and first harmonic of the kink
  mode changes with time as the loop cools. A consequence of this is
  that the value of the period ratio P <SUB>1</SUB>/P <SUB>2</SUB>,
  a tool that is popular in magneto-seismological studies in coronal
  diagnostics, decreases from the value of a uniform loop, 2, as
  the temperature decreases. The rate of change in P <SUB>1</SUB>/P
  <SUB>2</SUB> is dependent upon the cooling timescale and is well
  within the observable range for typical EUV loops. Further to this,
  the magnitude of the anti-node shift of the eigenfunctions of the
  first harmonic is shown to continually increase as the loop cools,
  giving additional impetus to the use of spatial magneto-seismology
  of the solar atmosphere. Finally, we suggest that measurements of
  the rate of change in the eigenfunctions and eigenfrequencies of MHD
  oscillations can provide values for the cooling timescale and a further
  insight into the physics of coronal loops.

Title: The effect of elliptic shape on the period ratio
    P<SUB>1</SUB>/P<SUB>2</SUB> of emerging coronal loops
Authors: Morton, R. J.; Erdélyi, R.
Bibcode: 2009A&A...502..315M
Altcode:
  Aims: We determine the effect of an elliptical shape on the period
  ratio for the standing transversal oscillations of a longitudinally
  stratified coronal loop throughout its emergence from the low solar
  atmosphere into the ubiquitously magnetised corona. <BR />Methods:
  Under the assumption that elliptical curvature has a negligible effect
  on eigenfrequencies, the equation that describes the projection of a
  density profile onto a magnetic flux tube with elliptical shape is
  obtained in a gravitationally stratified atmosphere. The effect of
  the elliptical shape on the period ratio of the fundamental mode to
  the first harmonic (P<SUB>1</SUB>/P<SUB>2</SUB>) at various stages
  of emergence is determined, assuming that the oscillation periods are
  much shorter than the characteristic time scale of loop emergence. <BR
  />Results: We find that there are two separate cases of elliptical shape
  that occur, the minor ellipse and the major ellipse. It is then shown
  how the period ratio P<SUB>1</SUB>/P<SUB>2</SUB> is dependent upon the
  ellipticity (ɛ), the parameter characterising the stage of emergence
  (λ) and the density scale height (H). Ellipticity is found to make an
  important contribution to P<SUB>1</SUB>/P<SUB>2</SUB> for the minor
  ellipse when compared to its counterpart of standing oscillations of
  stratified loops with semi-circle or circle-arc shape. The major ellipse
  was found to have a lesser effect on the period ratio of standing
  oscillations. We also find the value of P<SUB>1</SUB>/P<SUB>2</SUB> is
  dependent upon the stage of emergence of the loop, where the greatest
  contribution from emergence to the ratio of P<SUB>1</SUB>/P<SUB>2</SUB>
  is when the loop is almost fully emerged. The important implication for
  magneto-seismological interpretations of the observations of oscillating
  coronal loops is that measurements of ellipticity and stage of emergence
  should supplement observations of oscillation periods and should be
  considered when applying observed frequencies of the fundamental
  mode and first harmonic to determine the diagnostic properties of
  these oscillating loops, e.g. the density scale height or strength of
  magnetic field. Neglecting the determination of ellipticity and stage of
  emergence may result in a 35% error in estimating density scale height.

Title: Magnetohydrodynamic waves in a compressible magnetic flux
    tube with elliptical cross-section
Authors: Erdélyi, R.; Morton, R. J.
Bibcode: 2009A&A...494..295E
Altcode:
  Aims: The propagation of magnetohydrodynamic (MHD) waves in a finite,
  compressible magnetic flux tube with an elliptical cross-section
  embedded in a magnetic environment is investigated. <BR />Methods: We
  present the derivation of the general dispersion relation of linear
  magneto-acoustic wave propagation for a compressible magnetic flux
  tube with elliptical cross-section in a plasma with finite beta. The
  wave modes of propagation for the n=0 (symmetric) sausage and n=1
  (anti-symmetric) kink oscillations are then examined within the limit
  of the thin flux tube approximation. <BR />Results: It is shown that
  a compressible magnetic tube with elliptical cross-section supports
  slow and fast magneto-acoustic waves. In the thin tube approximation,
  the slow sausage mode and the slow and fast kink modes are found in
  analogue to a circular cross-section. However, the kink modes propagate
  with different phase speeds depending on whether the axial displacement
  takes place along the major or minor axis of the ellipse. This feature
  is present in both the slow and the fast bands, providing two infinite
  sets of slow kink modes and two infinite sets of fast kink modes,
  i.e. each corresponding cylindrical mode splits into two sets of modes
  due to the ellipticity. The difference between the phase speeds along
  the different axis is dependent on the ratio of the lengths of the two
  axes. Analytical expressions for the phase speeds are found. We show
  that the sausage modes do not split due to the introduced ellipticity
  and only the phase speed is modified when compared to the appropriate
  cylindrical counterpart. The percentage difference between the periods
  of the circular and elliptical cross-sections is also calculated, which
  reaches up to 21% for oscillations along the major axis. The level of
  difference in period could be very important in magneto-seismological
  applications, when observed periods are inverted into diagnostic
  properties (e.g. magnetic field strength, gravitational scale height,
  tube expansion parameter). Also shown is the perturbation of focal
  points of the elliptical cross-section for different modes. It is
  found that the focal points are unperturbed for the sausage mode,
  but are perturbed for all higher modes.

Title: Removal of diamond-turning signatures on x-ray mandrels and
    metal optics by fluid-jet polishing
Authors: Beaucamp, A.; Freeman, R.; Morton, R.; Ponudurai, Karthik;
   Walker, D. D.
Bibcode: 2008SPIE.7018E..35B
Altcode: 2008SPIE.7018E.100B
  This paper describes a major advance in the post-treatment of
  diamond-turned surfaces to remove repetitive micro-structure; a
  result which could have a major beneficial impact on fabrication
  of Walter-type X-ray mandrels, and metal mirrors. Diamond-turning
  is highly deterministic and versatile in producing axially-symmetric
  forms, and through fast-tool servos, non-axially symmetric, free-form
  and micro-structured surfaces. However, the fine turning marks left in
  the metal surface limit performance. In this paper, we describe how
  fluid-jet polishing under CNC control can be used to eliminate these
  structures, without significantly degrading the surface roughness or
  form produced by the prior turning operation.

Title: Active control of edges and global microstructure on segmented
    mirrors
Authors: Walker, D. D.; Beaucamp, A.; Dunn, C.; Evans, R.; Freeman,
   R.; Morton, R.; Wei, S.; Yu, G.
Bibcode: 2008SPIE.7018E..12W
Altcode: 2008SPIE.7018E..31W
  In this paper we address two interrelated issues important to primary
  mirror segments for extremely large telescopes - edge-control, and the
  detailed topography over the segment surface. Both affect the intensity
  and distribution of stray light and infrared emissivity. CNC polishing
  processes typically deploy spiral or raster tool-paths, tending to
  leave repetitive features. We compare and contrast two novel families
  of pseudo-random tool-paths for Precessions CNC polishing. We then
  show how CNC control of the three-dimensional tool-path can optimize
  edge-profiles. Finally, we demonstrate fluid-jet polishing used to
  clean up residual edge defects.

Title: Automated optical fabrication: first results from the new
    Precessions 1.2m CNC polishing machine
Authors: Walker, D. D.; Beaucamp, A. T. H.; Doubrovski, V.; Dunn,
   C.; Evans, R.; Freeman, R.; Kelchner, J.; McCavana, G.; Morton, R.;
   Riley, D.; Simms, J.; Yu, G.; Wei, X.
Bibcode: 2006SPIE.6273E..09W
Altcode: 2006SPIE.6273E...8W
  The requirements of space and defence optical systems and
  ground-based astronomy (especially extremely large telescopes) are
  providing optical fabricators with new challenges. These challenges
  particularly concern process speed, determinism and automation, and
  tighter tolerances on surface form and texture. Moreover, there is
  a growing demand for complex off-axis and 'freeform' surfaces and
  for larger components of the ~1m scale. With this in view, we first
  report on form-correction on a smaller analogue of the IRP1200:
  an IRP400 in service in industry. We then report on the design,
  commissioning and preliminary process-development results from
  the first of the scaled-up 1.2m capacity CNC polishing machine from
  Zeeko, Ltd. This machine delivers the 'Classic' bonnet-based process,
  together with two new processes: fluid-jet polishing and the hybrid
  soft-grinding/polishing process called 'Zeeko-Grolish.' We indicate
  how this trio of processes running on the same machine platform with
  unified software can provide an unprecedented dynamic range in both
  volumetric removal rate and removal spot-size. This leads into a
  discussion of how these processes may be brought to bear on optimal
  control of texture and form. Preliminary performance of the 1.2m machine
  is illustrated with results on both axially-symmetric and more complex
  removal regimes. The paper concludes with an overview of the relevance
  of the technology to efficient production of instrumentation-optics,
  space optics and segmented telescope mirrors.

Title: Recent advances in the control of form and texture on
    free-form surfaces
Authors: Walker, D. D.; Beaucamp, A. T.; Doubrovski, V.; Dunn, C.;
   Freeman, R.; Hobbs, G.; McCavana, G.; Morton, R.; Riley, D.; Simms,
   J.; Wei, X.
Bibcode: 2005SPIE.5965..249W
Altcode:
  The recent upsurge in the demand for off-axis and complex "freeform"
  optical surfaces is driving the development of novel processes for
  their fabrication. This paper focuses on recent developments of the
  Precessions CNC polishing process for freeform surfaces, including
  off-axis as a special case. First, the surface-prescription and
  metrology-data, and their relation to the data-input for the polishing
  machines, are considered. The relevance of consistent coordinate
  frames is emphasised. An outline of how the process can 'polish' a
  ground freeform part (improve the texture), and then 'figure' the part
  (reduce the form errors) is given. Specific experimental case-studies
  are then presented, illustrating the versatility of the process on
  different materials and forms. Recent work is included in which the
  process-speed has been moderated in order to remove tens of nanometres
  of stock material, rather then the more usual hundreds of nanometres to
  tens of microns as in the standard Precessions process. The relevance
  of this to improving the ultimate surface-precision that should be
  achievable by this method is described. As a final illustration, the
  potential of the process to the rapid fabrication of the hundreds to
  thousands of 1-2 metre class mirror segments required for extremely
  large telescopes is considered.

Title: New results extending the Precessions process to smoothing
    ground aspheres and producing freeform parts
Authors: Walker, D. D.; Beaucamp, A. T. H.; Doubrovski, V.; Dunn, C.;
   Freeman, R.; McCavana, G.; Morton, R.; Riley, D.; Simms, J.; Wei, X.
Bibcode: 2005SPIE.5869...79W
Altcode:
  Zeeko's Precession polishing process uses a bulged, rotating membrane
  tool, creating a contact-area of variable size. In separate modes
  of operation, the bonnet rotation-axis is orientated pole-down on
  the surface, or inclined at an angle and then precessed about the
  local normal. The bonnet, covered with standard polishing cloth and
  working with standard slurry, has been found to give superb surface
  textures in the regime of nanometre to sub-nanometre Ra values,
  starting with parts directly off precision CNC aspheric grinding
  machines. This paper reports an important extension of the process to
  the precision-controlled smoothing (or 'fining') operation required
  between more conventional diamond milling and subsequent Precession
  polishing. The method utilises an aggressive surface on the bonnet,
  again with slurry. This is compared with an alternative approach
  using diamond abrasives bound onto flexible carriers attached to the
  bonnets. The results demonstrate the viability of smoothing aspheric
  surfaces, which extends Precessions processing to parts with inferior
  input-quality. This may prove of particular importance to large optics
  where significant volumes of material may need to be removed, and to
  the creation of more substantial aspheric departures from a parent
  sphere. The paper continues with a recent update on results obtained,
  and lessons learnt, processing free-form surfaces, and concludes with an
  assessment of the relevance of the smoothing and free-form operations
  to the fabrication of off-axis parts including segments for extremely
  large telescopes.

Title: Kinetics of suprathermal hydrogen atom reactions with saturated
    hydrides in planetary and satellite atmospheres
Authors: Morton, Richard J.; Kaiser, Ralf I.
Bibcode: 2003P&SS...51..365M
Altcode:
  The kinetics of saturated hydrides methane (CH <SUB>4</SUB>),
  silane (SiH <SUB>4</SUB>), germane (GeH <SUB>4</SUB>), ammonia (NH
  <SUB>3</SUB>), phosphine (PH <SUB>3</SUB>), arsane (AsH <SUB>3</SUB>),
  water (H <SUB>2</SUB>O), and hydrogen sulfide (H <SUB>2</SUB>S) in
  the low-temperature atmospheres of Jupiter, Saturn, Uranus, Neptune,
  Pluto, Titan, and Triton reacting with suprathermal hydrogen atoms were
  investigated computationally to extract suprathermal rate constants k(
  E) via an inverse Laplace transformation from experimentally available
  thermal rate constants k( T). Our data reveal that all suprathermal rate
  constants range up to 10 <SUP>-10</SUP> cm<SUP>3</SUP> s<SUP>-1</SUP>,
  whereas the thermal counterparts are as low as 8×10 <SUP>-73</SUP>
  cm<SUP>3</SUP> s<SUP>-1</SUP>. These data demonstrate explicitly
  a significantly enhanced reactivity of photolytically generated
  suprathermal hydrogen atoms in the low-temperature planetary and
  satellite atmospheres and suggest that this hitherto unaccounted
  reaction class should be included by the planetary modeling community
  into future photochemical networks of atmospheres of outer solar system
  planets and their moons.

Title: Book-Review - Creative Computer Graphics
Authors: Jankel, A.; Morton, R.; Dearing, A.
Bibcode: 1985Natur.314..688J
Altcode:
  No abstract at ADS

Title: The statistical analysis and interpretation of
    imperfectly-fitted Rb-Sr isochrons from polymetamorphic terrains
    (reply to a comment by H. Austrheim)
Authors: Cameron, M.; Collerson, K. D.; Compston, W.; Morton, R.
Bibcode: 1983GeCoA..47..659C
Altcode:
  No abstract at ADS

Title: The statistical analysis and interpretation of
    imperfectly-fitted Rb-Sr isochrons from polymetamorphic terrains
Authors: Cameron, M.; Collerson, K. D.; Compston, W.; Morton, R.
Bibcode: 1981GeCoA..45.1087C
Altcode:
  Rb-Sr isotopic data for large, relatively homogeneous, whole-rock
  samples of Uivak 1 gneiss from the Saglek-Hebron area of northern
  Labrador exhibit a scatter which exceeds that predicted by experimental
  error. Isotopic analyses of adjacent compositionally-different layers
  of Uivak gneiss, 1-2 cm in width, define secondary isochrons,
  with slopes corresponding to an age of ca. 1800 Ma. As field
  evidence combined with previous isotopic dating demonstrates that
  the compositional layering did not form at this time, the secondary
  isochrons are interpreted as resulting from localized Sr-isotopic
  homogenization along <SUP>87</SUP>Sr abundance gradients generated
  by ageing in the previously-layered gneisses. The geological scatter
  in the larger gneiss specimens is therefore attributed to the same
  phenomenon on a reduced scale, viz. Sr isotopic equilibration at 1800
  Ma between adjacent volumes of gneiss. However regional differences
  in mean <SUP>87</SUP>Sr /<SUP>86</SUP>Sr and mean <SUP>87</SUP>Rb
  /<SUP>86</SUP>Sr are assumed to be unchanged. This interpretation
  has led us to the development of a weighted least squares regression
  technique that utilizes the geologically-induced error structure in
  the whole-rock Rb-Sr data. The method encompasses three models. In the
  first, the ' Local Isotopic Equilibrium' or ' Free-line' model, it is
  assumed that the error structure in the whole-rock samples is the same
  as that in the layered gneisses except for an unknown scaling factor,
  common to both <SUP>87</SUP>Rb /<SUP>86</SUP>Sr and <SUP>87</SUP>Sr
  /<SUP>86</SUP>Sr . In the other two models, the initial strontium
  isotopic composition is constrained to values greater than primordial
  Sr and corresponding to that expected for the contemporary 'Bulk
  Earth' by forcing the least squares fit for the data to pass through
  a fixed-point that corresponds to the present-day <SUP>87</SUP>Rb
  /<SUP>86</SUP>Sr and <SUP>87</SUP>Sr /<SUP>86</SUP>Sr composition of
  the Bulk Earth viz. approximately 0.085 and 0.7047 respectively. In the
  first of these models, ' Bulk Earth Model 1', no assumptions are made
  about the error structure of the primary data. An estimate of the age
  can be obtained but no estimate of its uncertainty. In the second, '
  Bulk Earth Model 2', the first two methods are combined and estimates
  for both the age and its 95% confidence limits may be found. In
  developing the method, nineteen whole-rock samples plus the means of
  the slabbed gneisses yielded the following results for the age and
  initial <SUP>87</SUP>Sr /<SUP>86</SUP>Sr , respectively, of the Uivak
  1 gneisses: (1) Free-line Model: 3621 <SUB>-410</SUB><SUP>+686</SUP>
  Ma, 0.70006 <SUB>-565</SUB><SUP>+354</SUP> <P />(2) Bulk Earth
  Model 1: 3606 Ma, 0.70020 <P />(3) Bulk Earth Model 2: 3606
  <SUB>-175</SUB><SUP>+213</SUP>Ma, 0.70020 <SUB>-27</SUB><SUP>+22</SUP>

