morton

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

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Title: Alfvénic waves in the inhomogeneous solar atmosphere
Authors: Morton, R. J.; Sharma, R.; Tajfirouzhe, E.; Miriyala, H.
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.

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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
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.

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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.
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.

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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
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.

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Title: Is phase mixing important in the quiet Sun?
Authors: Morton, Richard; McLaughlin, James; Tiwari, Ajay; Van
Doorsselaere, Tom
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.

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Title: Tracking the Alfven Waves in Closed Coronal Structure
Authors: Tajfirouze, Edris; Morton, Richard; Asgari-Targhi, Mahboubeh
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.

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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.
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.

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Title: A Statistical Study of Propagating MHD Kink Waves in the
Quiescent Corona
Authors: Tiwari, Ajay K.; Morton, Richard J.; McLaughlin, James A.
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.

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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
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.

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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
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.

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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.
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. This article is part of the Theo Murphy meeting issue
`High-resolution wave dynamics in the lower solar atmosphere'.

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Title: Transverse motions in sunspot super-penumbral fibrils
Authors: Morton, R. J.; Mooroogen, K.; Henriques, V. M. J.
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. This article is
part of the Theo Murphy meeting issue `High-resolution wave dynamics
in the lower solar atmosphere'.

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Title: Effect of coronal loop structure on wave heating through
phase mixing
Authors: Pagano, P.; De Moortel, I.; Morton, R. J.
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. 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. 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. 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. 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. 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>

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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
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.

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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.
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
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
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
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.
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.
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-1. 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.
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 corona1. Cutting-edge
observations and simulations are providing insights into the
underlying wave generation2, configuration3,4 and
damping5 mechanisms found in sunspot atmospheres. However,
the in situ amplification of magnetohydrodynamic waves6,
rising from a few hundreds of metres per second in the photosphere to
several kilometres per second in the chromosphere7, 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 resonator8-10, which
is created due to the substantial temperature gradients experienced
at photospheric and transition region heights11. 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 cavities12.

---------------------------------------------------------
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.
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.
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
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.
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
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.
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.
2019NatAs...3..223M Altcode: 2019arXiv190203811M; 2019NatAs.tmp..196M
Many cool stars possess complex magnetic fields1 that are
considered to undertake a central role in the structuring and energizing
of their atmospheres2. 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
winds3-5. 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 cells4,6,7. 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
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
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.
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.
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.
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.
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 cm2 @ 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.

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Title: Dynamics of internetwork chromospheric fibrils: Basic
properties and magnetohydrodynamic kink waves
Authors: Mooroogen, K.; Morton, R. J.; Henriques, V.
2017A&A...607A..46M Altcode: 2017arXiv170803500M
 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. 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. 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.

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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.
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.

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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.
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. 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. 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. 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. 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>

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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.
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).

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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.
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.
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.
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.
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 ⊙ with CoMP
Authors: Morton, R. J.; Tomczyk, S.; Pinto, R. F.
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.
2016A&A...593A..59M Altcode: 2016arXiv160705905M
 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. 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. 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.

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Title: Tornados and Transverse Oscillations during Prominence Eruption
Authors: Banerjee, Dipankar; Chandrashekhar, K.; Morton, Richard;
Pant, Vaibhav; Datta, Ajanta
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.
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.

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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.
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.

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Title: Investigating Alfvénic wave propagation in coronal open-field
regions
Authors: Morton, R. J.; Tomczyk, S.; Pinto, R.
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.
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.

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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.
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
D1, and Na i D1-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-2. 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.

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Title: First Direct Measurements of Transverse Waves in Solar Polar
Plumes Using SDO/AIA
Authors: Thurgood, J. O.; Morton, R. J.; McLaughlin, J. A.
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-1, and mean and standard deviations of
407 ± 297 km, 173 ± 118 s, and 14 ± 10 km s-1. 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-2, 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.

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Title: High-resolution Observations of Active Region Moss and its
Dynamics
Authors: Morton, R. J.; McLaughlin, J. A.
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-1
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.

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Title: Dynamic moss observed with Hi-C
Authors: Alexander, Caroline; Winebarger, Amy R.; Morton, Richard;
Savage, Sabrina
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.

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Title: Magneto-seismological insights into the penumbral chromosphere
and evidence for wave damping in spicules
Authors: Morton, R. J.
2014A&A...566A..90M Altcode: 2014arXiv1405.3203M
 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. 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. 
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.
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.
2014A&A...562A..98C Altcode: 2013arXiv1310.7853C
 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. 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. 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-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-1. 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. 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
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
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
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.
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.
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-1. 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.
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.
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-1. 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. 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.
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
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
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.
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 deg2). 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.
2012cosp...39.1883S Altcode: 2012cosp.meet.1883S
No abstract at ADS

---------------------------------------------------------
Title: Chromospheric jets around the edges of sunspots
Authors: Morton, R. J.
2012A&A...543A...6M Altcode: 2012arXiv1205.2307M
 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. 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. 
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-1 and a range of 10-100
km s-1. 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. 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.
2012A&A...542A..70M Altcode: 2012arXiv1204.5033M
 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. 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. 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-1 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. 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.
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.
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 × 104, 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.
2011A&A...534A..27M Altcode:
 Aims: We study the properties of torsional Alfvén waves in
coronal loops so that they may be exploited for coronal seismological
applications. 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. 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.
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 deg2 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.
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.
2011A&A...527A..53M Altcode: 2010arXiv1011.2377M
 Aims: We study kink and fluting oscillations of a straight
magnetic tube with an elliptic cross-section and density varying
along the tube. 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. 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.
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.
2010A&A...519A..43M Altcode:
 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. 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. 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.
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.
2010A&A...512A..23M Altcode:
 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. 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. 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.
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 1/P 2,
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 1/P
2 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
P1/P2 of emerging coronal loops
Authors: Morton, R. J.; Erdélyi, R.
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. 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 (P1/P2) at various stages
of emergence is determined, assuming that the oscillation periods are
much shorter than the characteristic time scale of loop emergence. 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 P1/P2 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 P1/P2 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 P1/P2 is
dependent upon the stage of emergence of the loop, where the greatest
contribution from emergence to the ratio of P1/P2
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.
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. 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. 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.
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.
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.
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.
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.
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.
2003P&SS...51..365M Altcode:
The kinetics of saturated hydrides methane (CH 4),
silane (SiH 4), germane (GeH 4), ammonia (NH
3), phosphine (PH 3), arsane (AsH 3),
water (H 2O), and hydrogen sulfide (H 2S) 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 -10 cm3 s-1,
whereas the thermal counterparts are as low as 8×10 -73
cm3 s-1. 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.
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.
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.
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 87Sr 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 87Sr /86Sr and mean 87Rb
/86Sr 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 87Rb /86Sr and 87Sr
/86Sr . 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 87Rb
/86Sr and 87Sr /86Sr 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 87Sr /86Sr , respectively, of the Uivak
1 gneisses: (1) Free-line Model: 3621 -410+686
Ma, 0.70006 -565+354 (2) Bulk Earth
Model 1: 3606 Ma, 0.70020 (3) Bulk Earth Model 2: 3606
-175+213Ma, 0.70020 -27+22