Author name code: morton ADS astronomy entries on 2022-09-14 author:"Morton, Richard J." ------------------------------------------------------------------------ Title: Alfvénic waves in the inhomogeneous solar atmosphere Authors: Morton, R. J.; Sharma, R.; Tajfirouzhe, E.; Miriyala, H. Bibcode: 2022arXiv220805222M Altcode: The solar atmosphere is known to be replete with magneto-hydrodynamic wave modes, and there has been significant investment in understanding how these waves propagate through the Sun's atmopshere and deposit their energy into the plasma. The waves' journey is made interesting by the vertical variation in plasma quantities that define the solar atmosphere. In addition to this large-scale inhomogeneity, a wealth of fine-scale structure through the chromosphere and corona has been brought to light by high-resolution observations over the last couple of decades. This fine-scale sturcture represents inhomogeneity that is thought to be perpendicular to the local magnetic fields. The implications of this form of inhomogeneity on wave propagation is still being uncovered, but is known to fundamentally change the nature of MHD wave modes. It also enables interesting physics to arise including resonances, turbulence and instabilities. Here we review some of the key insights into how the inhomogeneity influences Alfvénic wave propagation through the Sun's atmosphere, discussing both inhomogeneities parallel and perpendicular to the magnetic field. Title: Magnetoseismology for the solar corona: from 10 Gauss to coronal magnetograms Authors: Yang, Zihao; Gibson, Sarah; He, Jiansen; Del Zanna, Giulio; Tomczyk, Steven; Morton, Richard; McIntosh, Scott; Wang, Linghua; Karak, Bidya Binay; Samanta, Tanmoy; Tian, Hui; Chen, Yajie; Bethge, Christian; Bai, Xianyong Bibcode: 2022cosp...44.2490Y Altcode: Magnetoseismology, a technique of magnetic field diagnostics based on observations of magnetohydrodynamic (MHD) waves, has been widely used to estimate the field strengths of oscillating structures in the solar corona. However, previously magnetoseismology was mostly applied to occasionally occurring oscillation events, providing an estimate of only the average field strength or one-dimensional distribution of field strength along an oscillating structure. This restriction could be eliminated if we apply magnetoseismology to the pervasive propagating transverse MHD waves discovered with the Coronal Multi-channel Polarimeter (CoMP). Using several CoMP observations of the Fe XIII 1074.7 nm and 1079.8 nm spectral lines, we obtained maps of the plasma density and wave phase speed in the corona, which allow us to map both the strength and direction of the coronal magnetic field in the plane of sky. We also examined distributions of the electron density and magnetic field strength, and compared their variations with height in the quiet Sun and active regions. Such measurements could provide critical information to advance our understanding of the Sun's magnetism and the magnetic coupling of the whole solar atmosphere. Title: Parallel Plasma Loops and the Energization of the Solar Corona Authors: Peter, Hardi; Chitta, Lakshmi Pradeep; Chen, Feng; Pontin, David I.; Winebarger, Amy R.; Golub, Leon; Savage, Sabrina L.; Rachmeler, Laurel A.; Kobayashi, Ken; Brooks, David H.; Cirtain, Jonathan W.; De Pontieu, Bart; McKenzie, David E.; Morton, Richard J.; Testa, Paola; Tiwari, Sanjiv K.; Walsh, Robert W.; Warren, Harry P. Bibcode: 2022ApJ...933..153P Altcode: 2022arXiv220515919P The outer atmosphere of the Sun is composed of plasma heated to temperatures well in excess of the visible surface. We investigate short cool and warm (<1 MK) loops seen in the core of an active region to address the role of field-line braiding in energizing these structures. We report observations from the High-resolution Coronal imager (Hi-C) that have been acquired in a coordinated campaign with the Interface Region Imaging Spectrograph (IRIS). In the core of the active region, the 172 Å band of Hi-C and the 1400 Å channel of IRIS show plasma loops at different temperatures that run in parallel. There is a small but detectable spatial offset of less than 1″ between the loops seen in the two bands. Most importantly, we do not see observational signatures that these loops might be twisted around each other. Considering the scenario of magnetic braiding, our observations of parallel loops imply that the stresses put into the magnetic field have to relax while the braiding is applied: the magnetic field never reaches a highly braided state on these length scales comparable to the separation of the loops. This supports recent numerical 3D models of loop braiding in which the effective dissipation is sufficiently large that it keeps the magnetic field from getting highly twisted within a loop. Title: Magnetoseismology for the solar corona: from 10 Gauss to coronal magnetograms Authors: Yang, Zihao; Bethge, Christian; Tian, Hui; Tomczyk, Steven; Morton, Richard; Del Zanna, Giulio; McIntosh, Scott; Karak, Bidya Binay; Gibson, Sarah; Samanta, Tanmoy; He, Jiansen; Chen, Yajie; Bai, Xianyong; Wang, Linghua Bibcode: 2021AGUFMSH12C..07Y Altcode: Magnetoseismology, a technique of magnetic field diagnostics based on observations of magnetohydrodynamic (MHD) waves, has been widely used to estimate the field strengths of oscillating structures in the solar corona. However, previously magnetoseismology was mostly applied to occasionally occurring oscillation events, providing an estimate of only the average field strength or one-dimensional distribution of field strength along an oscillating structure. This restriction could be eliminated if we apply magnetoseismology to the pervasive propagating transverse MHD waves discovered with the Coronal Multi-channel Polarimeter (CoMP). Using several CoMP observations of the Fe XIII 1074.7 nm and 1079.8 nm spectral lines, we obtained maps of the plasma density and wave phase speed in the corona, which allow us to map both the strength and direction of the coronal magnetic field in the plane of sky. We also examined distributions of the electron density and magnetic field strength, and compared their variations with height in the quiet Sun and active regions. Such measurements could provide critical information to advance our understanding of the Sun's magnetism and the magnetic coupling of the whole solar atmosphere. Title: Is phase mixing important in the quiet Sun? Authors: Morton, Richard; McLaughlin, James; Tiwari, Ajay; Van Doorsselaere, Tom Bibcode: 2021AGUFMSH12B..09M Altcode: The focus of many investigations on coronal wave heating has been to scrutinise the role of transverse (i.e. kink) modes; examining their damping by resonant absorption and the transfer of energy to Alfvén modes. Subsequently, the Alfvén modes are then subject to phase mixing and this leads to plasma heating. More recently, a non-linear mechanism for energy transfer has also been proposed, the so called uni-turbulence. Due to the ease with which they have been observed, the rapidly damped standing kink modes in active regions have spawned numerous studies investigating the role of resonant absorption in the observed damping. However, their counterparts in the quiet Sun, the propagating kink waves, have received little attention. Here I will discuss the results from a large-scale study of kink wave damping in the quiet Sun. We find convincing evidence that the damping of the kink waves is significantly weaker than in active regions and suggests that resonant absorption/phase mixing/uni-turbulence are not important mechanisms for wave-based heating of the quiescent Sun. I will also discuss the physical reason we suspect is behind this result and what it tells us about the fine-scale structure of the quiescent corona. Title: Tracking the Alfven Waves in Closed Coronal Structure Authors: Tajfirouze, Edris; Morton, Richard; Asgari-Targhi, Mahboubeh Bibcode: 2021AGUFMSH25A2080T Altcode: Alfvén waves are potential candidates to explain the heating of the solar corona, since they can propagate long distances from the source where they originate up to the corona without significant damping. They are believed to be driven by the turbulent convective motions in the photosphere, and predominantly propagate upwards into the corona along network magnetic fields. However, the mechanism by which they convert their energy into plasma heating is still under debate. One scenario is that counter propagating Alfvén waves can interact nonlinearly and create turbulence. Energy cascades from the larger scales to small scale where it can be dissipated, e.g., by viscosity and resistivity. To date, observations of Alfvénic waves in the corona have been limited. The Coronal Multi-Channel Polarimeter (CoMP) provides remote observations of the off-limb corona, and has revealed Alfvénic velocity fluctuations are ubiquitous. The observations are currently limited to examining parallel wavenumbers, with the velocity power spectral density displaying power law behaviour that possess a range of spectral indices across the corona. The slope of the power spectra is related to the parallel correlation time of the waves in the corona. Given that the photospheric motions should have the same correlation time across the Sun (maybe with the exception of active regions), this may indicate that the different coronal spectral indices are the results of different magnetic/plasma conditions influencing the evolution of the waves through the lower solar atmosphere. Here, we present results on how Alfvén waves are influenced by different magnetic field conditions using a Reduced Magneto Hydrodynamic (RMHD) model which incorporates the wave turbulence and describes the propagation and dissipation of Alfvén waves along a single flux tube. Title: Weak Damping of Propagating MHD Kink Waves in the Quiescent Corona Authors: Morton, Richard J.; Tiwari, Ajay K.; Van Doorsselaere, Tom; McLaughlin, James A. Bibcode: 2021ApJ...923..225M Altcode: 2021arXiv210511924M Propagating transverse waves are thought to be a key transporter of Poynting flux throughout the Sun's atmosphere. Recent studies have shown that these transverse motions, interpreted as the magnetohydrodynamic kink mode, are prevalent throughout the corona. The associated energy estimates suggest the waves carry enough energy to meet the demands of coronal radiative losses in the quiescent Sun. However, it is still unclear how the waves deposit their energy into the coronal plasma. We present the results from a large-scale study of propagating kink waves in the quiescent corona using data from the Coronal Multi-channel Polarimeter (CoMP). The analysis reveals that the kink waves appear to be weakly damped, which would imply low rates of energy transfer from the large-scale transverse motions to smaller scales via either uniturbulence or resonant absorption. This raises questions about how the observed kink modes would deposit their energy into the coronal plasma. Moreover, these observations, combined with the results of Monte Carlo simulations, lead us to infer that the solar corona displays a spectrum of density ratios, with a smaller density ratio (relative to the ambient corona) in quiescent coronal loops and a higher density ratio in active-region coronal loops. Title: A Statistical Study of Propagating MHD Kink Waves in the Quiescent Corona Authors: Tiwari, Ajay K.; Morton, Richard J.; McLaughlin, James A. Bibcode: 2021ApJ...919...74T Altcode: 2021arXiv210512451T The Coronal Multi-channel Polarimeter (CoMP) has opened up exciting opportunities to probe transverse MHD waves in the Sun's corona. The archive of CoMP data is utilized to generate a catalog of quiescent coronal loops that can be used for studying propagating kink waves. The catalog contains 120 loops observed between 2012 and 2014. This catalog is further used to undertake a statistical study of propagating kink waves in the quiet regions of the solar corona, investigating phase speeds, loop lengths, footpoint power ratio (a measure of wave power entering the corona through each footpoint of a loop) and equilibrium parameter (which provides a measure of the change in wave amplitude) values. The statistical study enables us to establish the presence of a relationship between the rate of damping and the length of the coronal loop, with longer coronal loops displaying weaker wave damping. We suggest the reason for this behavior is related to a decreasing average density contrast between the loop and ambient plasma as loop length increases. The catalog presented here will provide the community with the foundation for the further study of propagating kink waves in the quiet solar corona. Title: Mapping the global magnetic field in the solar corona through magnetoseismology Authors: Yang, Zihao; Bethge, Christian; Tian, Hui; Tomczyk, Steven; Morton, Richard; Del Zanna, Giulio; McIntosh, Scott; Karak, Bidya Binay; Gibson, Sarah; Samanta, Tanmoy; He, Jiansen; Chen, Yajie; Wang, Linghua; Bai, Xianyong Bibcode: 2021EGUGA..23..642Y Altcode: Magnetoseismology, a technique of magnetic field diagnostics based on observations of magnetohydrodynamic (MHD) waves, has been widely used to estimate the field strengths of oscillating structures in the solar corona. However, previously magnetoseismology was mostly applied to occasionally occurring oscillation events, providing an estimate of only the average field strength or one-dimensional distribution of field strength along an oscillating structure. This restriction could be eliminated if we apply magnetoseismology to the pervasive propagating transverse MHD waves discovered with the Coronal Multi-channel Polarimeter (CoMP). Using several CoMP observations of the Fe XIII 1074.7 nm and 1079.8 nm spectral lines, we obtained maps of the plasma density and wave phase speed in the corona, which allow us to map both the strength and direction of the coronal magnetic field in the plane of sky. We also examined distributions of the electron density and magnetic field strength, and compared their variations with height in the quiet Sun and active regions. Such measurements could provide critical information to advance our understanding of the Sun's magnetism and the magnetic coupling of the whole solar atmosphere. Title: Critical Science Plan for the Daniel K. Inouye Solar Telescope (DKIST) Authors: Rast, Mark P.; Bello González, Nazaret; Bellot Rubio, Luis; Cao, Wenda; Cauzzi, Gianna; Deluca, Edward; de Pontieu, Bart; Fletcher, Lyndsay; Gibson, Sarah E.; Judge, Philip G.; Katsukawa, Yukio; Kazachenko, Maria D.; Khomenko, Elena; Landi, Enrico; Martínez Pillet, Valentín; Petrie, Gordon J. D.; Qiu, Jiong; Rachmeler, Laurel A.; Rempel, Matthias; Schmidt, Wolfgang; Scullion, Eamon; Sun, Xudong; Welsch, Brian T.; Andretta, Vincenzo; Antolin, Patrick; Ayres, Thomas R.; Balasubramaniam, K. S.; Ballai, Istvan; Berger, Thomas E.; Bradshaw, Stephen J.; Campbell, Ryan J.; Carlsson, Mats; Casini, Roberto; Centeno, Rebecca; Cranmer, Steven R.; Criscuoli, Serena; Deforest, Craig; Deng, Yuanyong; Erdélyi, Robertus; Fedun, Viktor; Fischer, Catherine E.; González Manrique, Sergio J.; Hahn, Michael; Harra, Louise; Henriques, Vasco M. J.; Hurlburt, Neal E.; Jaeggli, Sarah; Jafarzadeh, Shahin; Jain, Rekha; Jefferies, Stuart M.; Keys, Peter H.; Kowalski, Adam F.; Kuckein, Christoph; Kuhn, Jeffrey R.; Kuridze, David; Liu, Jiajia; Liu, Wei; Longcope, Dana; Mathioudakis, Mihalis; McAteer, R. T. James; McIntosh, Scott W.; McKenzie, David E.; Miralles, Mari Paz; Morton, Richard J.; Muglach, Karin; Nelson, Chris J.; Panesar, Navdeep K.; Parenti, Susanna; Parnell, Clare E.; Poduval, Bala; Reardon, Kevin P.; Reep, Jeffrey W.; Schad, Thomas A.; Schmit, Donald; Sharma, Rahul; Socas-Navarro, Hector; Srivastava, Abhishek K.; Sterling, Alphonse C.; Suematsu, Yoshinori; Tarr, Lucas A.; Tiwari, Sanjiv; Tritschler, Alexandra; Verth, Gary; Vourlidas, Angelos; Wang, Haimin; Wang, Yi-Ming; NSO and DKIST Project; DKIST Instrument Scientists; DKIST Science Working Group; DKIST Critical Science Plan Community Bibcode: 2021SoPh..296...70R Altcode: 2020arXiv200808203R The National Science Foundation's Daniel K. Inouye Solar Telescope (DKIST) will revolutionize our ability to measure, understand, and model the basic physical processes that control the structure and dynamics of the Sun and its atmosphere. The first-light DKIST images, released publicly on 29 January 2020, only hint at the extraordinary capabilities that will accompany full commissioning of the five facility instruments. With this Critical Science Plan (CSP) we attempt to anticipate some of what those capabilities will enable, providing a snapshot of some of the scientific pursuits that the DKIST hopes to engage as start-of-operations nears. The work builds on the combined contributions of the DKIST Science Working Group (SWG) and CSP Community members, who generously shared their experiences, plans, knowledge, and dreams. Discussion is primarily focused on those issues to which DKIST will uniquely contribute. Title: An overall view of temperature oscillations in the solar chromosphere with ALMA Authors: Jafarzadeh, S.; Wedemeyer, S.; Fleck, B.; Stangalini, M.; Jess, D. B.; Morton, R. J.; Szydlarski, M.; Henriques, V. M. J.; Zhu, X.; Wiegelmann, T.; Guevara Gómez, J. C.; Grant, S. D. T.; Chen, B.; Reardon, K.; White, S. M. Bibcode: 2021RSPTA.37900174J Altcode: 2021RSTPA.379..174J; 2020arXiv201001918J By direct measurements of the gas temperature, the Atacama Large Millimeter/submillimeter Array (ALMA) has yielded a new diagnostic tool to study the solar chromosphere. Here, we present an overview of the brightness-temperature fluctuations from several high-quality and high-temporal-resolution (i.e. 1 and 2 s cadence) time series of images obtained during the first 2 years of solar observations with ALMA, in Band 3 and Band 6, centred at around 3 mm (100 GHz) and 1.25 mm (239 GHz), respectively. The various datasets represent solar regions with different levels of magnetic flux. We perform fast Fourier and Lomb-Scargle transforms to measure both the spatial structuring of dominant frequencies and the average global frequency distributions of the oscillations (i.e. averaged over the entire field of view). We find that the observed frequencies significantly vary from one dataset to another, which is discussed in terms of the solar regions captured by the observations (i.e. linked to their underlying magnetic topology). While the presence of enhanced power within the frequency range 3-5 mHz is found for the most magnetically quiescent datasets, lower frequencies dominate when there is significant influence from strong underlying magnetic field concentrations (present inside and/or in the immediate vicinity of the observed field of view). We discuss here a number of reasons which could possibly contribute to the power suppression at around 5.5 mHz in the ALMA observations. However, it remains unclear how other chromospheric diagnostics (with an exception of Hα line-core intensity) are unaffected by similar effects, i.e. they show very pronounced 3-min oscillations dominating the dynamics of the chromosphere, whereas only a very small fraction of all the pixels in the 10 ALMA datasets analysed here show peak power near 5.5 mHz.

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

This article is part of the Theo Murphy meeting issue `High-resolution wave dynamics in the lower solar atmosphere'. Title: Effect of coronal loop structure on wave heating through phase mixing Authors: Pagano, P.; De Moortel, I.; Morton, R. J. Bibcode: 2020A&A...643A..73P Altcode: 2020arXiv200904366P Context. The mechanism(s) behind coronal heating still elude(s) direct observation and modelling of viable theoretical processes and the subsequent effect on coronal structures is one of the key tools available to assess possible heating mechanisms. Wave heating via the phase mixing of magnetohydrodynamic (MHD) transverse waves has been proposed as a possible way to convert magnetic energy into thermal energy, but MHD models increasingly suggest this is not an efficient enough mechanism.
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 https://www.aanda.org Title: Mapping the magnetic field in the solar corona through magnetoseismology Authors: Yang, ZiHao; Tian, Hui; Tomczyk, Steven; Morton, Richard; Bai, XianYong; Samanta, Tanmoy; Chen, YaJie Bibcode: 2020ScChE..63.2357Y Altcode: 2020arXiv200803146Y Magnetoseismology, a technique of magnetic field diagnostics based on observations of magnetohydrodynamic (MHD) waves, has been widely used to estimate the field strengths of oscillating structures in the solar corona. However, previously magnetoseismology was mostly applied to occasionally occurring oscillation events, providing an estimate of only the average field strength or one-dimensional distribution of field strength along an oscillating structure. This restriction could be eliminated if we apply magnetoseismology to the pervasive propagating transverse MHD waves discovered with the Coronal Multi-channel Polarimeter (CoMP). Using several CoMP observations of the Fe xiii 1074.7 nm and 1079.8 nm spectral lines, we obtained maps of the plasma density and wave phase speed in the corona, which allow us to map both the strength and direction of the coronal magnetic field in the plane of sky. We also examined distributions of the electron density and magnetic field strength, and compared their variations with height in the quiet Sun and active regions. Such measurements could provide critical information to advance our understanding of the Sun's magnetism and the magnetic coupling of the whole solar atmosphere. Title: The Solar Orbiter Science Activity Plan. Translating solar and heliospheric physics questions into action Authors: Zouganelis, I.; De Groof, A.; Walsh, A. P.; Williams, D. R.; Müller, D.; St Cyr, O. C.; Auchère, F.; Berghmans, D.; Fludra, A.; Horbury, T. S.; Howard, R. A.; Krucker, S.; Maksimovic, M.; Owen, C. J.; Rodríguez-Pacheco, J.; Romoli, M.; Solanki, S. K.; Watson, C.; Sanchez, L.; Lefort, J.; Osuna, P.; Gilbert, H. R.; Nieves-Chinchilla, T.; Abbo, L.; Alexandrova, O.; Anastasiadis, A.; Andretta, V.; Antonucci, E.; Appourchaux, T.; Aran, A.; Arge, C. N.; Aulanier, G.; Baker, D.; Bale, S. D.; Battaglia, M.; Bellot Rubio, L.; Bemporad, A.; Berthomier, M.; Bocchialini, K.; Bonnin, X.; Brun, A. S.; Bruno, R.; Buchlin, E.; Büchner, J.; Bucik, R.; Carcaboso, F.; Carr, R.; Carrasco-Blázquez, I.; Cecconi, B.; Cernuda Cangas, I.; Chen, C. H. K.; Chitta, L. P.; Chust, T.; Dalmasse, K.; D'Amicis, R.; Da Deppo, V.; De Marco, R.; Dolei, S.; Dolla, L.; Dudok de Wit, T.; van Driel-Gesztelyi, L.; Eastwood, J. P.; Espinosa Lara, F.; Etesi, L.; Fedorov, A.; Félix-Redondo, F.; Fineschi, S.; Fleck, B.; Fontaine, D.; Fox, N. J.; Gandorfer, A.; Génot, V.; Georgoulis, M. K.; Gissot, S.; Giunta, A.; Gizon, L.; Gómez-Herrero, R.; Gontikakis, C.; Graham, G.; Green, L.; Grundy, T.; Haberreiter, M.; Harra, L. K.; Hassler, D. M.; Hirzberger, J.; Ho, G. C.; Hurford, G.; Innes, D.; Issautier, K.; James, A. W.; Janitzek, N.; Janvier, M.; Jeffrey, N.; Jenkins, J.; Khotyaintsev, Y.; Klein, K. -L.; Kontar, E. P.; Kontogiannis, I.; Krafft, C.; Krasnoselskikh, V.; Kretzschmar, M.; Labrosse, N.; Lagg, A.; Landini, F.; Lavraud, B.; Leon, I.; Lepri, S. T.; Lewis, G. R.; Liewer, P.; Linker, J.; Livi, S.; Long, D. M.; Louarn, P.; Malandraki, O.; Maloney, S.; Martinez-Pillet, V.; Martinovic, M.; Masson, A.; Matthews, S.; Matteini, L.; Meyer-Vernet, N.; Moraitis, K.; Morton, R. J.; Musset, S.; Nicolaou, G.; Nindos, A.; O'Brien, H.; Orozco Suarez, D.; Owens, M.; Pancrazzi, M.; Papaioannou, A.; Parenti, S.; Pariat, E.; Patsourakos, S.; Perrone, D.; Peter, H.; Pinto, R. F.; Plainaki, C.; Plettemeier, D.; Plunkett, S. P.; Raines, J. M.; Raouafi, N.; Reid, H.; Retino, A.; Rezeau, L.; Rochus, P.; Rodriguez, L.; Rodriguez-Garcia, L.; Roth, M.; Rouillard, A. P.; Sahraoui, F.; Sasso, C.; Schou, J.; Schühle, U.; Sorriso-Valvo, L.; Soucek, J.; Spadaro, D.; Stangalini, M.; Stansby, D.; Steller, M.; Strugarek, A.; Štverák, Š.; Susino, R.; Telloni, D.; Terasa, C.; Teriaca, L.; Toledo-Redondo, S.; del Toro Iniesta, J. C.; Tsiropoula, G.; Tsounis, A.; Tziotziou, K.; Valentini, F.; Vaivads, A.; Vecchio, A.; Velli, M.; Verbeeck, C.; Verdini, A.; Verscharen, D.; Vilmer, N.; Vourlidas, A.; Wicks, R.; Wimmer-Schweingruber, R. F.; Wiegelmann, T.; Young, P. R.; Zhukov, A. N. Bibcode: 2020A&A...642A...3Z Altcode: 2020arXiv200910772Z Solar Orbiter is the first space mission observing the solar plasma both in situ and remotely, from a close distance, in and out of the ecliptic. The ultimate goal is to understand how the Sun produces and controls the heliosphere, filling the Solar System and driving the planetary environments. With six remote-sensing and four in-situ instrument suites, the coordination and planning of the operations are essential to address the following four top-level science questions: (1) What drives the solar wind and where does the coronal magnetic field originate?; (2) How do solar transients drive heliospheric variability?; (3) How do solar eruptions produce energetic particle radiation that fills the heliosphere?; (4) How does the solar dynamo work and drive connections between the Sun and the heliosphere? Maximising the mission's science return requires considering the characteristics of each orbit, including the relative position of the spacecraft to Earth (affecting downlink rates), trajectory events (such as gravitational assist manoeuvres), and the phase of the solar activity cycle. Furthermore, since each orbit's science telemetry will be downloaded over the course of the following orbit, science operations must be planned at mission level, rather than at the level of individual orbits. It is important to explore the way in which those science questions are translated into an actual plan of observations that fits into the mission, thus ensuring that no opportunities are missed. First, the overarching goals are broken down into specific, answerable questions along with the required observations and the so-called Science Activity Plan (SAP) is developed to achieve this. The SAP groups objectives that require similar observations into Solar Orbiter Observing Plans, resulting in a strategic, top-level view of the optimal opportunities for science observations during the mission lifetime. This allows for all four mission goals to be addressed. In this paper, we introduce Solar Orbiter's SAP through a series of examples and the strategy being followed. Title: Global maps of the magnetic field in the solar corona Authors: Yang, Zihao; Bethge, Christian; Tian, Hui; Tomczyk, Steven; Morton, Richard; Del Zanna, Giulio; McIntosh, Scott W.; Karak, Bidya Binay; Gibson, Sarah; Samanta, Tanmoy; He, Jiansen; Chen, Yajie; Wang, Linghua Bibcode: 2020Sci...369..694Y Altcode: 2020arXiv200803136Y Understanding many physical processes in the solar atmosphere requires determination of the magnetic field in each atmospheric layer. However, direct measurements of the magnetic field in the Sun’s corona are difficult to obtain. Using observations with the Coronal Multi-channel Polarimeter, we have determined the spatial distribution of the plasma density in the corona and the phase speed of the prevailing transverse magnetohydrodynamic waves within the plasma. We combined these measurements to map the plane-of-sky component of the global coronal magnetic field. The derived field strengths in the corona, from 1.05 to 1.35 solar radii, are mostly 1 to 4 gauss. Our results demonstrate the capability of imaging spectroscopy in coronal magnetic field diagnostics. Title: Observation and Modeling of High-temperature Solar Active Region Emission during the High-resolution Coronal Imager Flight of 2018 May 29 Authors: Warren, Harry P.; Reep, Jeffrey W.; Crump, Nicholas A.; Ugarte-Urra, Ignacio; Brooks, David H.; Winebarger, Amy R.; Savage, Sabrina; De Pontieu, Bart; Peter, Hardi; Cirtain, Jonathan W.; Golub, Leon; Kobayashi, Ken; McKenzie, David; Morton, Richard; Rachmeler, Laurel; Testa, Paola; Tiwari, Sanjiv; Walsh, Robert Bibcode: 2020ApJ...896...51W Altcode: Excellent coordinated observations of NOAA active region 12712 were obtained during the flight of the High-resolution Coronal Imager (Hi-C) sounding rocket on 2018 May 29. This region displayed a typical active region core structure with relatively short, high-temperature loops crossing the polarity inversion line and bright "moss" located at the footpoints of these loops. The differential emission measure (DEM) in the active region core is very sharply peaked at about 4 MK. Further, there is little evidence for impulsive heating events in the moss, even at the high spatial resolution and cadence of Hi-C. This suggests that active region core heating is occurring at a high frequency and keeping the loops close to equilibrium. To create a time-dependent simulation of the active region core, we combine nonlinear force-free extrapolations of the measured magnetic field with a heating rate that is dependent on the field strength and loop length and has a Poisson waiting time distribution. We use the approximate solutions to the hydrodynamic loop equations to simulate the full ensemble of active region core loops for a range of heating parameters. In all cases, we find that high-frequency heating provides the best match to the observed DEM. For selected field lines, we solve the full hydrodynamic loop equations, including radiative transfer in the chromosphere, to simulate transition region and chromospheric emission. We find that for heating scenarios consistent with the DEM, classical signatures of energy release, such as transition region brightenings and chromospheric evaporation, are weak, suggesting that they would be difficult to detect. Title: The Drivers of Active Region Outflows into the Slow Solar Wind Authors: Brooks, David H.; Winebarger, Amy R.; Savage, Sabrina; Warren, Harry P.; De Pontieu, Bart; Peter, Hardi; Cirtain, Jonathan W.; Golub, Leon; Kobayashi, Ken; McIntosh, Scott W.; McKenzie, David; Morton, Richard; Rachmeler, Laurel; Testa, Paola; Tiwari, Sanjiv; Walsh, Robert Bibcode: 2020ApJ...894..144B Altcode: 2020arXiv200407461B Plasma outflows from the edges of active regions have been suggested as a possible source of the slow solar wind. Spectroscopic measurements show that these outflows have an enhanced elemental composition, which is a distinct signature of the slow wind. Current spectroscopic observations, however, do not have sufficient spatial resolution to distinguish what structures are being measured or determine the driver of the outflows. The High-resolution Coronal Imager (Hi-C) flew on a sounding rocket in 2018 May and observed areas of active region outflow at the highest spatial resolution ever achieved (250 km). Here we use the Hi-C data to disentangle the outflow composition signatures observed with the Hinode satellite during the flight. We show that there are two components to the outflow emission: a substantial contribution from expanded plasma that appears to have been expelled from closed loops in the active region core and a second contribution from dynamic activity in active region plage, with a composition signature that reflects solar photospheric abundances. The two competing drivers of the outflows may explain the variable composition of the slow solar wind. Title: Using Transverse Waves to Probe the Plasma Conditions at the Base of the Solar Wind Authors: Weberg, Micah J.; Morton, Richard J.; McLaughlin, James A. Bibcode: 2020ApJ...894...79W Altcode: It has long been suggested that magnetohydrodynamic (MHD) waves may supply a significant proportion of the energy required to heat the corona and accelerate the solar wind. Depending on the properties of the local plasma, MHD wave modes may exhibit themselves as a variety of incompressible, transverse waves. The local magnetic field and particle density influence the properties of these waves (e.g., amplitude), thus direct measurements of transverse waves provide a mechanism to indirectly probe the local plasma conditions. We present the first statistical approach to magnetoseismology of a localized region of the solar corona, analyzing transverse waves above the south polar coronal hole on 2011 May 23. Automated methods are utilized to examine 4 hr of EUV imaging data to study how the waves evolve as a function of height (I.e., altitude) through the low corona. Between heights of 15 and 35 Mm, we find that the measured wave periods are approximately constant, and that observed displacement and velocity amplitudes increase at rates that are consistent with undamped waves. This enables us to derive a relative density profile for the coronal hole environment in question, without the use of spectroscopic data. Furthermore, our results indicate that between 5 and 15 Mm above the limb, the relative density is larger than that expected from 1D hydrostatic models, and signals a more extended transition region with a gradual change in density. This has implications for self-consistent models of wave propagation from the photosphere to the corona and beyond. Title: Is the High-Resolution Coronal Imager Resolving Coronal Strands? Results from AR 12712 Authors: Williams, Thomas; Walsh, Robert W.; Winebarger, Amy R.; Brooks, David H.; Cirtain, Jonathan W.; De Pontieu, Bart; Golub, Leon; Kobayashi, Ken; McKenzie, David E.; Morton, Richard J.; Peter, Hardi; Rachmeler, Laurel A.; Savage, Sabrina L.; Testa, Paola; Tiwari, Sanjiv K.; Warren, Harry P.; Watkinson, Benjamin J. Bibcode: 2020ApJ...892..134W Altcode: 2020arXiv200111254W Following the success of the first mission, the High-Resolution Coronal Imager (Hi-C) was launched for a third time (Hi-C 2.1) on 2018 May 29 from the White Sands Missile Range, NM, USA. On this occasion, 329 s of 17.2 nm data of target active region AR 12712 were captured with a cadence of ≈4 s, and a plate scale of 0.129 arcsec pixel-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. Bibcode: 2020NatAs...4..220J Altcode: 2019NatAs...4..220J; 2019NatAs.tmp..502J Sunspots are intense collections of magnetic fields that pierce through the Sun's photosphere, with their signatures extending upwards into the outermost extremities of the solar 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. Bibcode: 2019ApJ...887L...8P Altcode: 2019arXiv191102331P We present high-resolution, high-cadence observations of six, fine-scale, on-disk jet-like events observed by the High-resolution Coronal Imager 2.1 (Hi-C 2.1) during its sounding-rocket flight. We combine the Hi-C 2.1 images with images from the Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA) and the Interface Region Imaging Spectrograph (IRIS), and investigate each event’s magnetic setting with co-aligned line-of-sight magnetograms from the SDO/Helioseismic and Magnetic Imager (HMI). We find that (i) all six events are jetlet-like (having apparent properties of jetlets), (ii) all six are rooted at edges of magnetic network lanes, (iii) four of the jetlet-like events stem from sites of flux cancelation between majority-polarity network flux and merging minority-polarity flux, and (iv) four of the jetlet-like events show brightenings at their bases reminiscent of the base brightenings in coronal jets. The average spire length of the six jetlet-like events (9000 ± 3000 km) is three times shorter than that for IRIS jetlets (27,000 ± 8000 km). While not ruling out other generation mechanisms, the observations suggest that at least four of these events may be miniature versions of both larger-scale coronal jets that are driven by minifilament eruptions and still-larger-scale solar eruptions that are driven by filament eruptions. Therefore, we propose that our Hi-C events are driven by the eruption of a tiny sheared-field flux rope, and that the flux rope field is built and triggered to erupt by flux cancelation. Title: Fine-scale Explosive Energy Release at Sites of Prospective Magnetic Flux Cancellation in the Core of the Solar Active Region Observed by Hi-C 2.1, IRIS, and SDO Authors: Tiwari, Sanjiv K.; Panesar, Navdeep K.; Moore, Ronald L.; De Pontieu, Bart; Winebarger, Amy R.; Golub, Leon; Savage, Sabrina L.; Rachmeler, Laurel A.; Kobayashi, Ken; Testa, Paola; Warren, Harry P.; Brooks, David H.; Cirtain, Jonathan W.; McKenzie, David E.; Morton, Richard J.; Peter, Hardi; Walsh, Robert W. Bibcode: 2019ApJ...887...56T Altcode: 2019arXiv191101424T The second Hi-C flight (Hi-C 2.1) provided unprecedentedly high spatial and temporal resolution (∼250 km, 4.4 s) coronal EUV images of Fe IX/X emission at 172 Å of AR 12712 on 2018 May 29, during 18:56:21-19:01:56 UT. Three morphologically different types (I: dot-like; II: loop-like; III: surge/jet-like) of fine-scale sudden-brightening events (tiny microflares) are seen within and at the ends of an arch filament system in the core of the AR. Although type Is (not reported before) resemble IRIS bombs (in size, and brightness with respect to surroundings), our dot-like events are apparently much hotter and shorter in span (70 s). We complement the 5 minute duration Hi-C 2.1 data with SDO/HMI magnetograms, SDO/AIA EUV images, and IRIS UV spectra and slit-jaw images to examine, at the sites of these events, brightenings and flows in the transition region and corona and evolution of magnetic flux in the photosphere. Most, if not all, of the events are seated at sites of opposite-polarity magnetic flux convergence (sometimes driven by adjacent flux emergence), implying likely flux cancellation at the microflare’s polarity inversion line. In the IRIS spectra and images, we find confirming evidence of field-aligned outflow from brightenings at the ends of loops of the arch filament system. In types I and II the explosion is confined, while in type III the explosion is ejective and drives jet-like outflow. The light curves from Hi-C, AIA, and IRIS peak nearly simultaneously for many of these events, and none of the events display a systematic cooling sequence as seen in typical coronal flares, suggesting that these tiny brightening events have chromospheric/transition region origin. Title: The High-Resolution Coronal Imager, Flight 2.1 Authors: Rachmeler, Laurel A.; Winebarger, Amy R.; Savage, Sabrina L.; Golub, Leon; Kobayashi, Ken; Vigil, Genevieve D.; Brooks, David H.; Cirtain, Jonathan W.; De Pontieu, Bart; McKenzie, David E.; Morton, Richard J.; Peter, Hardi; Testa, Paola; Tiwari, Sanjiv K.; Walsh, Robert W.; Warren, Harry P.; Alexander, Caroline; Ansell, Darren; Beabout, Brent L.; Beabout, Dyana L.; Bethge, Christian W.; Champey, Patrick R.; Cheimets, Peter N.; Cooper, Mark A.; Creel, Helen K.; Gates, Richard; Gomez, Carlos; Guillory, Anthony; Haight, Harlan; Hogue, William D.; Holloway, Todd; Hyde, David W.; Kenyon, Richard; Marshall, Joseph N.; McCracken, Jeff E.; McCracken, Kenneth; Mitchell, Karen O.; Ordway, Mark; Owen, Tim; Ranganathan, Jagan; Robertson, Bryan A.; Payne, M. Janie; Podgorski, William; Pryor, Jonathan; Samra, Jenna; Sloan, Mark D.; Soohoo, Howard A.; Steele, D. Brandon; Thompson, Furman V.; Thornton, Gary S.; Watkinson, Benjamin; Windt, David Bibcode: 2019SoPh..294..174R Altcode: 2019arXiv190905942R The third flight of the High-Resolution Coronal Imager (Hi-C 2.1) occurred on May 29, 2018; the Sounding Rocket was launched from White Sands Missile Range in New Mexico. The instrument has been modified from its original configuration (Hi-C 1) to observe the solar corona in a passband that peaks near 172 Å, and uses a new, custom-built low-noise camera. The instrument targeted Active Region 12712, and captured 78 images at a cadence of 4.4 s (18:56:22 - 19:01:57 UT; 5 min and 35 s observing time). The image spatial resolution varies due to quasi-periodic motion blur from the rocket; sharp images contain resolved features of at least 0.47 arcsec. There are coordinated observations from multiple ground- and space-based telescopes providing an unprecedented opportunity to observe the mass and energy coupling between the chromosphere and the corona. Details of the instrument and the data set are presented in this paper. Title: Investigating “Dark” Energy in the Solar Corona Using Forward Modeling of MHD Waves Authors: Pant, Vaibhav; Magyar, Norbert; Van Doorsselaere, Tom; Morton, Richard J. Bibcode: 2019ApJ...881...95P Altcode: 2019arXiv190610941P It is now well established that Alfvénic waves are ubiquitous in the solar corona. However, the Alfvénic wave energy estimated from Doppler velocity measurements in the corona was found to be four orders of magnitude less than that estimated from nonthermal line widths. McIntosh & 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 & De Pontieu termed this coronal “dark” or “hidden” energy. However, their simulations required the use of an additional, unknown source of Alfvénic wave energy to obtain agreement with measurements of the coronal nonthermal line widths. In this study, we investigate the requirement of this unknown source of additional “dark” energy in the solar corona using gravitationally stratified 3D magnetohydrodynamic (MHD) simulations of propagating waves. We excite the transverse MHD waves and generate synthetic observations of the Fe XIII emission line. We establish that LOS superposition greatly reduces the Doppler velocity amplitudes and increases the nonthermal line widths. Importantly, our model generates the observed wedge-shape correlation between Doppler velocities and nonthermal line widths. We find that the observed wave energy is only 0.2%-1% of the true wave energy, which explains the 2-3 order-of-magnitude energy discrepancy. We conclusively establish that true wave energies are hidden in nonthermal line widths. Hence, our results rule out the requirement for an additional “dark” energy in the solar corona. Title: Exploring the Properties of Transverse Waves at the Base of the Solar Wind Authors: Weberg, Micah J.; Morton, Richard; McLaughlin, James; Laming, Martin; Ko, Yuan-Kuen Bibcode: 2019shin.confE.173W Altcode: Transverse (or ‘Alfvénic’) waves are commonly invoked by theories and models to explain coronal heating and solar wind acceleration. However, direct measurements are sparse and most of what we know is derived from indirect proxies for wave activity. In this study, we present a large, statistical study of transverse waves directly observed in coronal plumes between May 2010 and May 2019 by SDO / AIA. The data was processed using an automated version of the Northumbria University Wave Tracking Code (NUWT) and presents a detailed picture of wave properties at the base of the solar wind. We find that the bulk wave parameters within the time periods analysed are largely consistent over most of a solar cycle. However, there is some evidence for smaller-scale variations with height, latitude, and over time periods of a few years. We will also explore the possibility of frequency-dependant processes which may give limits on the height at which wave dissipation, and thereby solar wind acceleration, begins. Lastly, we will give estimates for the total energy flux contained in the waves and discuss how it compares to the energy required to accelerate the solar wind. Title: Damping of Propagating Kink Waves in the Solar Corona Authors: Tiwari, Ajay K.; Morton, Richard J.; Régnier, Stéphane; McLaughlin, James A. Bibcode: 2019ApJ...876..106T Altcode: 2019arXiv190408834T Alfvénic waves have gained renewed interest since the existence of ubiquitous propagating kink waves were discovered in the corona. It has long been suggested that Alfvénic waves play an important role in coronal heating and the acceleration of the solar wind. To this effect, it is imperative to understand the mechanisms that enable their energy to be transferred to the plasma. Mode conversion via resonant absorption is believed to be one of the main mechanisms for kink wave damping and it is considered to play a key role in the process of energy transfer. This study examines the damping of propagating kink waves in quiescent coronal loops using the Coronal Multi-channel Polarimeter. A coherence-based method is used to track the Doppler velocity signal of the waves, which enables us to investigate the spatial evolution of velocity perturbations. The power ratio of outward to inward propagating waves is used to estimate the associated damping lengths and quality factors. To enable accurate estimates of these quantities, we provide the first derivation of a likelihood function suitable for fitting models to the ratio of two power spectra obtained from discrete Fourier transforms. Maximum likelihood estimation is used to fit an exponential damping model to the observed variation in power ratio as a function of frequency. We confirm earlier indications that propagating kink waves are undergoing frequency-dependent damping. Additionally, we find that the rate of damping decreases, or equivalently the damping length increases, for longer coronal loops that reach higher in the corona. Title: A basal contribution from p-modes to the Alfvénic wave flux in the Sun's corona Authors: Morton, R. J.; Weberg, M. J.; McLaughlin, J. A. Bibcode: 2019NatAs...3..223M Altcode: 2019arXiv190203811M; 2019NatAs.tmp..196M Many cool stars possess complex magnetic 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 Bibcode: 2018csc..confE..70P Altcode: Magnetohydrodynamic (MHD) waves are ubiquitous in the solar atmosphere. These waves play an important role in the heating of solar corona. Recently, an apparent discrepancy is observed in the Alfvénic wave amplitudes measured by the Coronal Multi-channel Polarimeter (CoMP) compared to those measured by the Hinode and the Solar Dynamics Observatory (SDO). This discrepancy was attributed to a large line-of-sight superposition and low spatial resolution of the CoMP, which may lead to low wave amplitudes and large non-thermal line widths. A wedge-shape correlation is also observed between root mean square Doppler velocity and mean non-thermal line width. We investigate this scenario by performing a 3D MHD simulation of a gravitationally stratified transversely inhomogenous plasma subjected to the unidirectionally propagating MHD waves. Here, we present the results of this simulation forward modelled with the FoMo for Fe XIII (10747 Å) emission line to study the variation of Doppler velocities with non-thermal line widths. We perform the random integration over different line-of-sights angles across and along the simulation box. We degrade the spatial resolution of the simulation box to the spatial resolution of the CoMP and compare Doppler velocities and non-thermal line widths at different heights. We compare our results with previous studies as well as with observations made by the CoMP and find a fairly good match between them. Title: Photospheric Observations of Surface and Body Modes in Solar Magnetic Pores Authors: Keys, Peter H.; Morton, Richard J.; Jess, David B.; Verth, Gary; Grant, Samuel D. T.; Mathioudakis, Mihalis; Mackay, Duncan H.; Doyle, John G.; Christian, Damian J.; Keenan, Francis P.; Erdélyi, Robertus Bibcode: 2018ApJ...857...28K Altcode: 2018arXiv180301859K Over the past number of years, great strides have been made in identifying the various low-order magnetohydrodynamic wave modes observable in a number of magnetic structures found within the solar atmosphere. However, one aspect of these modes that has remained elusive, until now, is their designation as either surface or body modes. This property has significant implications for how these modes transfer energy from the waveguide to the surrounding plasma. Here, for the first time to our knowledge, we present conclusive, direct evidence of these wave characteristics in numerous pores that were observed to support sausage modes. As well as outlining methods to detect these modes in observations, we make estimates of the energies associated with each mode. We find surface modes more frequently in the data, as well as that surface modes appear to carry more energy than those displaying signatures of body modes. We find frequencies in the range of ∼2-12 mHz, with body modes as high as 11 mHz, but we do not find surface modes above 10 mHz. It is expected that the techniques we have applied will help researchers search for surface and body signatures in other modes and in differing structures from those presented here. Title: An Automated Algorithm for Identifying and Tracking Transverse Waves in Solar Images Authors: Weberg, Micah J.; Morton, Richard J.; McLaughlin, James A. Bibcode: 2018ApJ...852...57W Altcode: 2018arXiv180704842W Recent instrumentation has demonstrated that the solar atmosphere supports omnipresent transverse waves, which could play a key role in energizing the solar corona. Large-scale studies are required in order to build up an understanding of the general properties of these transverse waves. To help facilitate this, we present an automated algorithm for identifying and tracking features in solar images and extracting the wave properties of any observed transverse oscillations. We test and calibrate our algorithm using a set of synthetic data, which includes noise and rotational effects. The results indicate an accuracy of 1%-2% for displacement amplitudes and 4%-10% for wave periods and velocity amplitudes. We also apply the algorithm to data from the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory and find good agreement with previous studies. Of note, we find that 35%-41% of the observed plumes exhibit multiple wave signatures, which indicates either the superposition of waves or multiple independent wave packets observed at different times within a single structure. The automated methods described in this paper represent a significant improvement on the speed and quality of direct measurements of transverse waves within the solar atmosphere. This algorithm unlocks a wide range of statistical studies that were previously impractical. Title: Annual Properties of Transverse Waves in the Corona over most of Solar Cycle 24 Authors: Weberg, M. J.; Morton, R. J.; McLaughlin, J. A. Bibcode: 2017AGUFMSH42B..07W Altcode: Waves are an omnipresent feature in heliophysical plasmas. In particular, transverse (or "Alfvénic") waves have been observed at a wide range of spatial and temporal scales within the corona and solar wind. These waves play a key role in transporting energy through the solar atmosphere and are also thought to contribute to the heating and acceleration of the solar wind. Previous studies of low-frequency (< 10 mHz) transverse waves in coronal loops and polar plumes have provided tantalizing glimpses at specific time periods, however few, if any, systematic studies have been performed spanning long time scales. In this study, we combine recent advancements in the automated detection and measurement of low-frequency transverse waves with over 7 years of SDO / AIA data to provide a detailed picture of coronal transverse waves in polar plumes and, for the first time, begin to examine their long-term behaviour. We measure waves at three different heights in each of eight, four-hour periods spanning May 2010 - May 2017. We find that the bulk wave parameters within these 24 regions are largely consistent over most of a solar cycle. However, there is some evidence for smaller-scale variations both with height and over time periods of a few years. We also discuss total energy flux estimations based on the full wave power spectra, which yields a more nuanced picture than previous values based on summary statistics. Overall, this work expands our view of wave processes in the corona and is relevant to both theoretical and modelling considerations of energy transport within the solar atmosphere. Crucially, these initial results suggest that the energy flux provided by the low-frequency transverse waves varies little over the solar cycle, potentially indicating that the waves provide a consistent source of energy to the corona and beyond. Title: Measuring the magnetic field of a trans-equatorial loop system using coronal seismology (Corrigendum) Authors: Long, D. M.; Valori, G.; Pérez-Suárez, D.; Morton, R. J.; Vásquez, A. M. Bibcode: 2017A&A...607C...3L Altcode: No abstract at ADS Title: Design and development by direct polishing of the WFXT thin polynomial mirror shells Authors: Proserpio, L.; Campana, S.; Citterio, O.; Civitani, M.; Combrinck, H.; Conconi, P.; Cotroneo, V.; Freeman, R.; Mattini, E.; Langstrof, P.; Morton, R.; Motta, G.; Oberle, O.; Pareschi, G.; Parodi, G.; Pels, C.; Schenk, C.; Stock, R.; Tagliaferri, G. Bibcode: 2017SPIE10565E..2NP Altcode: The Wide Field X-ray Telescope (WFXT) is a medium class mission proposed to address key questions about cosmic origins and physics of the cosmos through an unprecedented survey of the sky in the soft X-ray band (0.2-6 keV) [1], [2]. In order to get the desired angular resolution of 10 arcsec (5 arcsec goal) on the entire 1 degrees Field Of View (FOV), the design of the optical system is based on nested grazing-incidence polynomial profiles mirrors, and assumes a focal plane curvature and plate scale corrections among the shells. This design guarantees an increased angular resolution also at large off-axis positions with respect to the usually adopted Wolter I configuration. In order to meet the requirements in terms of mass and effective area (less than 1200 kg, 6000 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. Title: Dynamics of internetwork chromospheric fibrils: Basic properties and magnetohydrodynamic kink waves Authors: Mooroogen, K.; Morton, R. J.; Henriques, V. Bibcode: 2017A&A...607A..46M Altcode: 2017arXiv170803500M
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. Title: The Frequency-dependent Damping of Slow Magnetoacoustic Waves in a Sunspot Umbral Atmosphere Authors: Krishna Prasad, S.; Jess, D. B.; Van Doorsselaere, T.; Verth, G.; Morton, R. J.; Fedun, V.; Erdélyi, R.; Christian, D. J. Bibcode: 2017ApJ...847....5K Altcode: 2017ApJ...847....5P; 2017arXiv170804835K High spatial and temporal resolution images of a sunspot, obtained simultaneously in multiple optical and UV wavelengths, are employed to study the propagation and damping characteristics of slow magnetoacoustic waves up to transition region heights. Power spectra are generated from intensity oscillations in sunspot umbra, across multiple atmospheric heights, for frequencies up to a few hundred mHz. It is observed that the power spectra display a power-law dependence over the entire frequency range, with a significant enhancement around 5.5 mHz found for the chromospheric channels. The phase difference spectra reveal a cutoff frequency near 3 mHz, up to which the oscillations are evanescent, while those with higher frequencies propagate upward. The power-law index appears to increase with atmospheric height. Also, shorter damping lengths are observed for oscillations with higher frequencies suggesting frequency-dependent damping. Using the relative amplitudes of the 5.5 mHz (3 minute) oscillations, we estimate the energy flux at different heights, which seems to decay gradually from the photosphere, in agreement with recent numerical simulations. Furthermore, a comparison of power spectra across the umbral radius highlights an enhancement of high-frequency waves near the umbral center, which does not seem to be related to magnetic field inclination angle effects. Title: Measuring the magnetic field of a trans-equatorial loop system using coronal seismology Authors: Long, D. M.; Valori, G.; Pérez-Suárez, D.; Morton, R. J.; Vásquez, A. M. Bibcode: 2017A&A...603A.101L Altcode: 2017arXiv170310020L Context. EIT waves are freely-propagating global pulses in the low corona which are strongly associated with the initial evolution of coronal mass ejections (CMEs). They are thought to be large-amplitude, fast-mode magnetohydrodynamic waves initially driven by the rapid expansion of a CME in the low corona.
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 http://www.aanda.org Title: Observational Signatures of a Kink-unstable Coronal Flux Rope Using Hinode/EIS Authors: Snow, B.; Botha, G. J. J.; Régnier, S.; Morton, R. J.; Verwichte, E.; Young, P. R. Bibcode: 2017ApJ...842...16S Altcode: 2017arXiv170505114S The signatures of energy release and energy transport for a kink-unstable coronal flux rope are investigated via forward modeling. Synthetic intensity and Doppler maps are generated from a 3D numerical simulation. The CHIANTI database is used to compute intensities for three Hinode/EIS emission lines that cover the thermal range of the loop. The intensities and Doppler velocities at simulation-resolution are spatially degraded to the Hinode/EIS pixel size (1″), convolved using a Gaussian point-spread function (3″), and exposed for a characteristic time of 50 s. The synthetic images generated for rasters (moving slit) and sit-and-stare (stationary slit) are analyzed to find the signatures of the twisted flux and the associated instability. We find that there are several qualities of a kink-unstable coronal flux rope that can be detected observationally using Hinode/EIS, namely the growth of the loop radius, the increase in intensity toward the radial edge of the loop, and the Doppler velocity following an internal twisted magnetic field line. However, EIS cannot resolve the small, transient features present in the simulation, such as sites of small-scale reconnection (e.g., nanoflares). Title: Project SunbYte: solar astronomy on a budget Authors: Alvarez Gonzalez, F.; Badilita, A. -M.; Baker, A.; Cho, Y. -H.; Dhot, N.; Fedun, V.; Hare, C.; He, T.; Hobbs, M.; Javed, M.; Lovesey, H.; Lord, C.; Panoutsos, G.; Permyakov, A.; Pope, S.; Portnell, M.; Rhodes, L.; Sharma, R.; Taras, P.; Taylor, J.; Tilbrook, R.; Verth, G.; Wrigley, S. N.; Yaqoob, M.; Cook, R.; McLaughlin, J.; Morton, R.; Scullion, E.; Shelyag, S.; Hamilton, A.; Zharkov, S.; Jess, D.; Wrigley, M. Bibcode: 2017A&G....58d2.24A Altcode: The Sheffield University Nova Balloon Lifted Solar Telescope (SunbYte) is a high-altitude balloon experiment devised and run largely by students at the University of Sheffield, and is scheduled for launch in October 2017. It was the only UK project in 2016 to be selected for the balloon side of the Swedish-German student programme REXUS/BEXUS (Rocket and Balloon Experiments for University Students; see box on p2.25). The success of the SunbYte team in the REXUS/BEXUS selection process is an unprecedented opportunity for the students to gain valuable experience working in the space engineering industry, using their theoretical knowledge and networking with students and technology companies from all over Europe. Title: Automating Direct Observations of Transverse Waves in the Solar Corona Authors: Weberg, M. J.; Morton, R. J.; McLaughlin, J. A. Bibcode: 2016AGUFMSH21E2576W Altcode: A multitude of MHD waves have been observed at a large range of scales in the solar atmosphere. According to theories and models, transverse (or "Alfvénic") waves are a viable mechanism for both heating and accelerating the solar wind and may also drive certain elemental fractionation processes in the chromosphere and corona. However, direct measurements of transverse waves in polar plumes (Thurgood et al. 2014) have raised some questions concerning the total energy carried by the waves and whether or not it is sufficient to be a primary driver of either solar wind heating or acceleration. In this work we build upon on the framework of Morton & McLaughlin (2013) and Thurgood et al. (2014) and extend the capabilities of the Northumbria University Wave Tracking (NUWT) code. In particular, we present an automated method of detecting and quantifying transverse waves in polar coronal holes. With the application of Fourier analysis methods, we investigate the superposition of multiple waves propagating along individual structures and, additionally, examine multi-variate relationships that may exist between wave parameters. We report the distributions of wave parameters for hundreds of waves observed using data from the 171 Å channel of SDO / AIA at select times throughout the solar cycle. Finally, we discuss how the measured average wave energy compares to theoretical predictions. The methods described in this research can be easily applied to other instruments, both space- and ground-based, and the observations of wave parameters and energetics place important constraints on wave-driven models of the solar corona. Title: The importance of high-resolution observations of the solar corona Authors: Winebarger, A. R.; Cirtain, J. W.; Golub, L.; Walsh, R. W.; De Pontieu, B.; Savage, S. L.; Rachmeler, L.; Kobayashi, K.; Testa, P.; Brooks, D.; Warren, H.; Mcintosh, S. W.; Peter, H.; Morton, R. J.; Alexander, C. E.; Tiwari, S. K. Bibcode: 2016AGUFMSH31B2577W Altcode: The spatial and temporal resolutions of the available coronal observatories are inadequate to resolve the signatures of coronal heating. High-resolution and high-cadence observations available with the Interface Region Imaging Spectrograph (IRIS) and the High-resolution Coronal Imager (Hi-C) instrument hint that 0.3 arcsec resolution images and < 10 s cadence provide the necessary resolution to detect heating events. Hi-C was launched from White Sands Missile Range on July 11, 2012 (before the launch with IRIS) and obtained images of a solar active region in the 19.3 nm passband. In this presentation, I will discuss the potential of combining a flight in Hi-C with a 17.1 nm passband, in conjunction with IRIS. This combination will provide, for the first time, a definitive method of tracing the energy flow between the chromosphere and corona and vice versa. Title: Exploring Coronal Dynamics: A Next Generation Solar Physics Mission white paper Authors: Morton, R. J.; Scullion, E.; Bloomfield, D. S.; McLaughlin, J. A.; Regnier, S.; McIntosh, S. W.; Tomczyk, S.; Young, P. Bibcode: 2016arXiv161106149M Altcode: Determining the mechanisms responsible for the heating of the coronal plasma and maintaining and accelerating the solar wind are long standing goals in solar physics. There is a clear need to constrain the energy, mass and momentum flux through the solar corona and advance our knowledge of the physical process contributing to these fluxes. Furthermore, the accurate forecasting of Space Weather conditions at the near-Earth environment and, more generally, the plasma conditions of the solar wind throughout the heliosphere, require detailed knowledge of these fluxes in the near-Sun corona. Here we present a short case for a space-based imaging-spectrometer coronagraph, which will have the ability to provide synoptic information on the coronal environment and provide strict constraints on the mass, energy, and momentum flux through the corona. The instrument would ideally achieve cadences of $\sim10$~s, spatial resolution of 1" and observe the corona out to 2~$R_{\sun}$. Such an instrument will enable significant progress in our understanding of MHD waves throughout complex plasmas, as well as potentially providing routine data products to aid Space Weather forecasting. Title: A Global View of Velocity Fluctuations in the Corona below 1.3 R ⊙ with CoMP Authors: Morton, R. J.; Tomczyk, S.; Pinto, R. F. Bibcode: 2016ApJ...828...89M Altcode: 2016arXiv160801831M The Coronal Multi-channel Polarimeter (CoMP) has previously demonstrated the presence of Doppler velocity fluctuations in the solar corona. The observed fluctuations are thought to be transverse waves, I.e., highly incompressible motions whose restoring force is dominated by the magnetic tension, some of which demonstrate clear periodicity. We aim to exploit CoMP’s ability to provide high cadence observations of the off-limb corona to investigate the properties of velocity fluctuations in a range of coronal features, providing insight into how (whether) the properties of the waves are influenced by the varying magnetic topology in active regions, quiet Sun and open field regions. An analysis of Doppler velocity time-series of the solar corona from the 10747 Å Iron xiii line is performed, determining the velocity power spectrum and using it as a tool to probe wave behavior. Further, the average phase speed and density for each region are estimated and used to compute the spectra for energy density and energy flux. In addition, we assess the noise levels associated with the CoMP data, deriving analytic formulae for the uncertainty on Doppler velocity measurements and providing a comparison by estimating the noise from the data. It is found that the entire corona is replete with transverse wave behavior. The corresponding power spectra indicate that the observed velocity fluctuations are predominately generated by stochastic processes, with the spectral slope of the power varying between the different magnetic regions. Most strikingly, all power spectra reveal the presence of enhanced power occurring at ∼3 mHz, potentially implying that the excitation of coronal transverse waves by p-modes is a global phenomenon. Title: Model fitting of kink waves in the solar atmosphere: Gaussian damping and time-dependence Authors: Morton, R. J.; Mooroogen, K. Bibcode: 2016A&A...593A..59M Altcode: 2016arXiv160705905M
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&A, 585, L6). Further, we use the model comparison to provide evidence of time-dependent wave properties of a kink oscillation, attributing the behaviour to the thermodynamic evolution of the local plasma. Title: Tornados and Transverse Oscillations during Prominence Eruption Authors: Banerjee, Dipankar; Chandrashekhar, K.; Morton, Richard; Pant, Vaibhav; Datta, Ajanta Bibcode: 2016cosp...41E.141B Altcode: We report and analyse different phases of a prominence eruption. The winding-unwinding of two footpoints and a tornado like swirling motion is studied. The prominence eruption is observed by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). This prominence eruption is associated with a CME at a central principal angle of 340 degree, according to the SOHO/LASCO CME catalogue. We can observe the prominence threads and the time distance maps reveal that the loop threads are entangled. We also study the transverse oscillations in the threads. Swirling motions after the eruptions are also quantified and its possible link with the CME kinematics is also studied Title: Nuwt: Northumbria University Wave Tracking (Nuwt) Code Authors: Morton, Richard J.; Mooroogen, Krishna; McLaughlin, James A. Bibcode: 2016zndo.....49563M Altcode: This is the first release of the Northumbria University Wave Tracking (NUWT) code (in IDL). The code is primarily designed to analyse transverse waves along curvilinear features in solar imaging data, however, the underlying operations will work on any images. Tutorials and videos are included with the release. Title: On the Properties of Slow MHD Sausage Waves within Small-scale Photospheric Magnetic Structures Authors: Freij, N.; Dorotovič, I.; Morton, R. J.; Ruderman, M. S.; Karlovský, V.; Erdélyi, R. Bibcode: 2016ApJ...817...44F Altcode: 2015arXiv150908680F The presence of magnetoacoustic waves in magnetic structures in the solar atmosphere is well-documented. Applying the technique of solar magneto-seismology (SMS) allows us to infer the background properties of these structures. Here, we aim to identify properties of the observed magnetoacoustic waves and study the background properties of magnetic structures within the lower solar atmosphere. Using the Dutch Open Telescope and Rapid Oscillations in the Solar Atmosphere instruments, we captured two series of high-resolution intensity images with short cadences of two isolated magnetic pores. Combining wavelet analysis and empirical mode decomposition (EMD), we determined characteristic periods within the cross-sectional (I.e., area) and intensity time series. Then, by applying the theory of linear magnetohydrodynamics (MHD), we identified the mode of these oscillations within the MHD framework. Several oscillations have been detected within these two magnetic pores. Their periods range from 3 to 20 minutes. Combining wavelet analysis and EMD enables us to confidently find the phase difference between the area and intensity oscillations. From these observed features, we concluded that the detected oscillations can be classified as slow sausage MHD waves. Furthermore, we determined several key properties of these oscillations such as the radial velocity perturbation, the magnetic field perturbation, and the vertical wavenumber using SMS. The estimated range of the related wavenumbers reveals that these oscillations are trapped within these magnetic structures. Our results suggest that the detected oscillations are standing harmonics, and this allows us to estimate the expansion factor of the waveguides by employing SMS. The calculated expansion factor ranges from 4 to 12. Title: Investigating Alfvénic wave propagation in coronal open-field regions Authors: Morton, R. J.; Tomczyk, S.; Pinto, R. Bibcode: 2015NatCo...6.7813M Altcode: 2015NatCo...6E7813M The physical mechanisms behind accelerating solar and stellar winds are a long-standing astrophysical mystery, although recent breakthroughs have come from models invoking the turbulent dissipation of Alfvén waves. The existence of Alfvén waves far from the Sun has been known since the 1970s, and recently the presence of ubiquitous Alfvénic waves throughout the solar atmosphere has been confirmed. However, the presence of atmospheric Alfvénic waves does not, alone, provide sufficient support for wave-based models; the existence of counter-propagating Alfvénic waves is crucial for the development of turbulence. Here, we demonstrate that counter-propagating Alfvénic waves exist in open coronal magnetic fields and reveal key observational insights into the details of their generation, reflection in the upper atmosphere and outward propagation into the solar wind. The results enhance our knowledge of Alfvénic wave propagation in the solar atmosphere, providing support and constraints for some of the recent Alfvén wave turbulence models. Title: Multiwavelength Studies of MHD Waves in the Solar Chromosphere. An Overview of Recent Results Authors: Jess, D. B.; Morton, R. J.; Verth, G.; Fedun, V.; Grant, S. D. T.; Giagkiozis, I. Bibcode: 2015SSRv..190..103J Altcode: 2015arXiv150301769J; 2015SSRv..tmp...14J The chromosphere is a thin layer of the solar atmosphere that bridges the relatively cool photosphere and the intensely heated transition region and corona. Compressible and incompressible waves propagating through the chromosphere can supply significant amounts of energy to the interface region and corona. In recent years an abundance of high-resolution observations from state-of-the-art facilities have provided new and exciting ways of disentangling the characteristics of oscillatory phenomena propagating through the dynamic chromosphere. Coupled with rapid advancements in magnetohydrodynamic wave theory, we are now in an ideal position to thoroughly investigate the role waves play in supplying energy to sustain chromospheric and coronal heating. Here, we review the recent progress made in characterising, categorising and interpreting oscillations manifesting in the solar chromosphere, with an impetus placed on their intrinsic energetics. Title: Wave Damping Observed in Upwardly Propagating Sausage-mode Oscillations Contained within a Magnetic Pore Authors: Grant, S. D. T.; Jess, D. B.; Moreels, M. G.; Morton, R. J.; Christian, D. J.; Giagkiozis, I.; Verth, G.; Fedun, V.; Keys, P. H.; Van Doorsselaere, T.; Erdélyi, R. Bibcode: 2015ApJ...806..132G Altcode: 2015arXiv150501484G We present observational evidence of compressible MHD wave modes propagating from the solar photosphere through to the base of the transition region in a solar magnetic pore. High cadence images were obtained simultaneously across four wavelength bands using the Dunn Solar Telescope. Employing Fourier and wavelet techniques, sausage-mode oscillations displaying significant power were detected in both intensity and area fluctuations. The intensity and area fluctuations exhibit a range of periods from 181 to 412 s, with an average period ∼290 s, consistent with the global p-mode spectrum. Intensity and area oscillations present in adjacent bandpasses were found to be out of phase with one another, displaying phase angles of 6.°12, 5.°82, and 15.°97 between the 4170 Å continuum-G-band, G-band-Na i 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. Title: First Direct Measurements of Transverse Waves in Solar Polar Plumes Using SDO/AIA Authors: Thurgood, J. O.; Morton, R. J.; McLaughlin, J. A. Bibcode: 2014ApJ...790L...2T Altcode: 2014arXiv1406.5348T There is intense interest in determining the precise contribution of Alfvénic waves propagating along solar structures to the problems of coronal heating and solar wind acceleration. Since the launch of SDO/AIA, it has been possible to resolve transverse oscillations in off-limb solar polar plumes and recently McIntosh et al. concluded that such waves are energetic enough to play a role in heating the corona and accelerating the fast solar wind. However, this result is based on comparisons to Monte Carlo simulations and confirmation via direct measurements is still outstanding. Thus, this Letter reports on the first direct measurements of transverse wave motions in solar polar plumes. Over a four hour period, we measure the transverse displacements, periods, and velocity amplitudes of 596 distinct oscillations observed in the 171 Å channel of SDO/AIA. We find a broad range of non-uniformly distributed parameter values which are well described by log-normal distributions with peaks at 234 km, 121 s, and 8 km s-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. Title: High-resolution Observations of Active Region Moss and its Dynamics Authors: Morton, R. J.; McLaughlin, J. A. Bibcode: 2014ApJ...789..105M Altcode: 2014arXiv1405.5694M The High Resolution Coronal Imager has provided the sharpest view of the EUV corona to date. In this paper, we exploit its impressive resolving power to provide the first analysis of the fine-scale structure of moss in an active region. The data reveal that the moss is made up of a collection of fine threads that have widths with a mean and standard deviation of 440 ± 190 km (FWHM). The brightest moss emission is located at the visible head of the fine-scale structure and the fine structure appears to extend into the lower solar atmosphere. The emission decreases along the features, implying that the lower sections are most likely dominated by cooler transition region plasma. These threads appear to be the cool, lower legs of the hot loops. In addition, the increased resolution allows for the first direct observation of physical displacements of the moss fine structure in a direction transverse to its central axis. Some of these transverse displacements demonstrate periodic behavior, which we interpret as a signature of kink (Alfvénic) waves. Measurements of the properties of the transverse motions are made and the wave motions have means and standard deviations of 55 ± 37 km for the transverse displacement amplitude, 77 ± 33 s for the period, and 4.7 ± 2.5 km s-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. Title: Dynamic moss observed with Hi-C Authors: Alexander, Caroline; Winebarger, Amy R.; Morton, Richard; Savage, Sabrina Bibcode: 2014AAS...22431206A Altcode: The High-resolution Coronal Imager (Hi-C), flown on 11 July 2012, has revealed an unprecedented level of detail and substructure within the solar corona. Hi-C imaged a large active region (AR11520) with 0.2-0.3’’ spatial resolution and 5.5s cadence over a 5 minute period. An additional dataset with a smaller FOV, the same resolution, but with a higher temporal cadence (1s) was also taken during the rocket flight. This dataset was centered on a large patch of ‘moss’ emission that initially seemed to show very little variability. Image processing revealed this region to be much more dynamic than first thought with numerous bright and dark features observed to appear, move and disappear over the 5 minute observation. Moss is thought to be emission from the upper transition region component of hot loops so studying its dynamics and the relation between the bright/dark features and underlying magnetic features is important to tie the interaction of the different atmospheric layers together. Hi-C allows us to study the coronal emission of the moss at the smallest scales while data from SDO/AIA and HMI is used to give information on these structures at different heights/temperatures. Using the high temporal and spatial resolution of Hi-C the observed moss features were tracked and the distribution of displacements, speeds, and sizes were measured. This allows us to comment on both the physical processes occurring within the dynamic moss and the scales at which these changes are occurring. Title: Magneto-seismological insights into the penumbral chromosphere and evidence for wave damping in spicules Authors: Morton, R. J. Bibcode: 2014A&A...566A..90M Altcode: 2014arXiv1405.3203M
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. Bibcode: 2014ApJ...784...29M Altcode: 2013arXiv1310.4650M The source of the non-thermal energy required for the heating of the upper solar atmosphere to temperatures in excess of a million degrees and the acceleration of the solar wind to hundreds of kilometers per second is still unclear. One such mechanism for providing the required energy flux is incompressible torsional Alfvén and kink magnetohydrodynamic (MHD) waves, which are magnetically dominated waves supported by the Sun's pervasive and complex magnetic field. In particular, propagating MHD kink waves have recently been observed to be ubiquitous throughout the solar atmosphere, but, until now, critical details of the transport of the kink wave energy throughout the Sun's atmosphere were lacking. Here, the ubiquity of the waves is exploited for statistical studies in the highly dynamic solar chromosphere. This large-scale investigation allows for the determination of the chromospheric kink wave velocity power spectra, a missing link necessary for determining the energy transport between the photosphere and corona. Crucially, the power spectra contain evidence for horizontal photospheric motions being an important mechanism for kink wave generation in the quiescent Sun. In addition, a comparison with measured coronal power spectra is provided for the first time, revealing frequency-dependent transmission profiles, suggesting that there is enhanced damping of kink waves in the lower corona. Title: The dynamical behaviour of a jet in an on-disk coronal hole observed with AIA/SDO Authors: Chandrashekhar, K.; Morton, R. J.; Banerjee, D.; Gupta, G. R. Bibcode: 2014A&A...562A..98C Altcode: 2013arXiv1310.7853C
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 http://www.aanda.org Title: Magneto-seismological insights into the penumbral chromosphere and evidence for wave damping in chromospheric wave-guides Authors: Morton, Richard Bibcode: 2014cosp...40E2180M Altcode: The observation of propagating magneto-hydrodynamic kink waves in magnetic structures and measurement of their properties (amplitude, phase speed) can be used to diagnose the plasma conditions in the neighbourhood of the magnetic structure via magneto-seismology. Hinode SOT observed a sunspot as it was crossing over the limb, providing a unique side on view of the Sunspot atmosphere. The presence of large spicule-like jets is evident in Ca II H images and they are found to support transverse (kink) motions. The properties of a specific wave event are measured and used to determine the magnetic and density stratification along the structure. In addition, we can measure the width of the spicule and the intensity profile along the structure in order to provide a test for the magneto-seismological results. I will discuss the techniques behind the measurements and what the seismological results can reveal about the chromosphere above a sunspot. These results are contrasted to the direct measurements of the spicule properties and a good agreement is found between measured and seismological-ly inferred quantities. Perhaps most importantly, we demonstrate that a combination of seismological and measured properties implies that an observed decrease in wave amplitude at greater heights is due to wave damping. Hence, the first evidence of wave damping in chromospheric wave-guides is provided. The quality factor of the damping is found to be significantly smaller than estimated coronal values. Title: Transverse Oscillations observed in a Jet and coronal seismology Authors: Banerjee, Dipankar; Chandrashekhar, K.; Morton, Richard Bibcode: 2014cosp...40E.204B Altcode: Extreme Ultra Violet (EUV) jets situated in coronal holes are thought to play an important role in supplying heated material to the corona and solar wind. The multi-wavelength capabilities and high signal-to-noise ratio of detectors on-board Solar Dynamic Observatory (SDO) allows for detailed study of these jet’s evolution. We aim to exploit SDO’s capabilities to reveal information on the jet dynamics and to obtain estimates for plasma properties associated with the jet. We studied the dynamics an EUV jet with SDO at a coronal hole boundary. The details of the jet evolution are discussed and measurements of the jet’s parameters, e.g. length, width, life time, and outward speed, are obtained. Furthermore, automated emission measure analysis is exploited to determine estimates for the temperature and density of the jet. A propagating transverse wave supported by the jet spire is also observed. Measurement of the wave properties are exploited for magneto-seismology and are used in conjunction with the emission measure results to estimate the magnetic field strength of the jet. We present a detailed description of the jet’s evolution, with new evidence of plasma flows, prior to the jet’s initiation, along the loops at the base of the jet and also find further evidence that flows along the jet spire consist of multiple, quasi-periodic small scale plasma ejection events. In addition, spectroscopic analysis reveal that the jet has temperatures of log 5.89 ±0.08 K and electron densities of log 8.75 ± 0.05 cm(-3) . Measured properties of the transverse wave provide evidence that a strong damping of the wave occurs as it propagates along the jet spire with speeds of 110 km/s. The magneto-seismological inversion of the wave parameters provides values of B = 1.21 ±0.2 G along the jet spire, which is in line with previous estimates for open fields in coronal holes. Title: High-resolution observations of active region moss and its dynamics Authors: Morton, Richard; McLaughlin, James Bibcode: 2014cosp...40E2181M Altcode: The High resolution Coronal Imager (Hi-C) has provided the sharpest view of the EUV corona to date. I will present results that exploit its impressive resolving power to provide the first analysis of the fine-scale structure of moss in an active region. The data reveal that the moss is made up of a collection of fine threads that have widths ranging between 400-1000 km. These fine-scale structures are connected to the bright moss and appear to extend into the lower solar atmosphere. The emission decreases along the features implying the lower sections are most likely dominated by cooler transition region plasma. These threads appear to be the cool, lower legs of the hot loops. The increased resolution also allows for the first direct observation of physical displacements of the moss fine-structure in a direction transverse to its central axis. Some of these transverse displacements demonstrate periodic behaviour, which we interpret as a signature of kink (Alfvénic) waves. The presence of waves in the transition region of hot loops could have important implications for the heating of active regions. Title: Characteristics of Transverse Waves in Chromospheric Mottles Authors: Kuridze, D.; Verth, G.; Mathioudakis, M.; Erdélyi, R.; Jess, D. B.; Morton, R. J.; Christian, D. J.; Keenan, F. P. Bibcode: 2013ApJ...779...82K Altcode: 2013arXiv1310.3628K Using data obtained by the high temporal and spatial resolution Rapid Oscillations in the Solar Atmosphere instrument on the Dunn Solar Telescope, we investigate at an unprecedented level of detail transverse oscillations in chromospheric fine structures near the solar disk center. The oscillations are interpreted in terms of propagating and standing magnetohydrodynamic kink waves. Wave characteristics including the maximum transverse velocity amplitude and the phase speed are measured as a function of distance along the structure's length. Solar magnetoseismology is applied to these measured parameters to obtain diagnostic information on key plasma parameters (e.g., magnetic field, density, temperature, flow speed) of these localized waveguides. The magnetic field strength of the mottle along the ~2 Mm length is found to decrease by a factor of 12, while the local plasma density scale height is ~280 ± 80 km. Title: A Statistical Study of Transverse Oscillations in a Quiescent Prominence Authors: Hillier, A.; Morton, R. J.; Erdélyi, R. Bibcode: 2013ApJ...779L..16H Altcode: 2013arXiv1310.8009H The launch of the Hinode satellite has allowed for seeing-free observations at high-resolution and high-cadence making it well suited to study the dynamics of quiescent prominences. In recent years it has become clear that quiescent prominences support small-amplitude transverse oscillations, however, sample sizes are usually too small for general conclusions to be drawn. We remedy this by providing a statistical study of transverse oscillations in vertical prominence threads. Over a 4 hr period of observations it was possible to measure the properties of 3436 waves, finding periods from 50 to 6000 s with typical velocity amplitudes ranging between 0.2 and 23 km s-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. Bibcode: 2013A&A...556C...1M Altcode: No abstract at ADS Title: Hi-C and AIA observations of transverse magnetohydrodynamic waves in active regions Authors: Morton, R. J.; McLaughlin, J. A. Bibcode: 2013A&A...553L..10M Altcode: 2013arXiv1305.0140M The recent launch of the High resolution Coronal imager (Hi-C) provided a unique opportunity of studying the EUV corona with unprecedented spatial resolution. We utilize these observations to investigate the properties of low-frequency (50-200 s) active region transverse waves, whose omnipresence had been suggested previously. The five-fold improvement in spatial resolution over SDO/AIA reveals coronal loops with widths 150-310 km and that these loops support transverse waves with displacement amplitudes <50 km. However, the results suggest that wave activity in the coronal loops is of low energy, with typical velocity amplitudes <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 http://www.aanda.org Title: Evidence for the Photospheric Excitation of Incompressible Chromospheric Waves Authors: Morton, R. J.; Verth, G.; Fedun, V.; Shelyag, S.; Erdélyi, R. Bibcode: 2013ApJ...768...17M Altcode: 2013arXiv1303.2356M Observing the excitation mechanisms of incompressible transverse waves is vital for determining how energy propagates through the lower solar atmosphere. We aim to show the connection between convectively driven photospheric flows and incompressible chromospheric waves. The observations presented here show the propagation of incompressible motion through the quiet lower solar atmosphere, from the photosphere to the chromosphere. We determine photospheric flow vectors to search for signatures of vortex motion and compare results to photospheric flows present in convective simulations. Further, we search for the chromospheric response to vortex motions. Evidence is presented that suggests incompressible waves can be excited by the vortex motions of a strong magnetic flux concentration in the photosphere. A chromospheric counterpart to the photospheric vortex motion is also observed, presenting itself as a quasi-periodic torsional motion. Fine-scale, fibril structures that emanate from the chromospheric counterpart support transverse waves that are driven by the observed torsional motion. A new technique for obtaining details of transverse waves from time-distance diagrams is presented and the properties of transverse waves (e.g., amplitudes and periods) excited by the chromospheric torsional motion are measured. Title: SDO/AIA observations of periodic and quasi-periodic phenomenon associated with an EUV jet Authors: Morton, Richard; Verth, Gary; Erdelyi, Robertus; Srivastava, Abhi Bibcode: 2013EGUGA..15...52M Altcode: It has long been advocated that explosive magnetic activity is responsible for the mass-balance in the solar atmosphere, supplying the corona and the solar wind with heated plasma. The explosive events are thought to be the result of emerging bi-polar (EB) regions reconnecting with pre-existing, open fields, with the size of the EB's (i.e., granular, super-granular) being related to size of the resulting feature (i.e., spicules, EUV/X-ray jets). Recent evidence has suggested a deeper relationship between spicules and EUV jets (Sterling et al., 2010). We present here observations of a EUV jet observed with SDO/AIA close to a southern coronal hole. The jet can be considered as a 'Blowout jet' (using the terminology of Moore et al., 2010), launching vast amounts of chromospheric plasma into the atmosphere along with hotter material. The hotter part of the jet appears to be composed of multiple, (quasi-)periodic ejections that individually resemble fast moving (>100 km/s) spicules. The multiple ejections appear crucial for distributing the hotter material high into the corona, possibly suggesting that larger EUV/X-ray are composed of many smaller spicule-like events. Although the event is close to the limb, evidence for reconnection at the chromospheric level is provided. Further, evidence for helicity (or torsional motion) and the presence of slow and fast Magnetohydrodynamic waves is given, with the wave mode excitation likely due to the reconnection process. Exploiting the observed wave motion, we also use magneto-seismological techniques to determine local plasma parameters with sub-resolution accuracy along one of the jets unique features. Title: Observations of ubiquitous compressive waves in the Sun's chromosphere Authors: Morton, Richard J.; Verth, Gary; Jess, David B.; Kuridze, David; Ruderman, Michael S.; Mathioudakis, Mihalis; Erdélyi, Robertus Bibcode: 2012NatCo...3.1315M Altcode: 2012NatCo...3E1315M; 2013arXiv1306.4124M The details of the mechanism(s) responsible for the observed heating and dynamics of the solar atmosphere still remain a mystery. Magnetohydrodynamic waves are thought to have a vital role in this process. Although it has been shown that incompressible waves are ubiquitous in off-limb solar atmospheric observations, their energy cannot be readily dissipated. Here we provide, for the first time, on-disk observation and identification of concurrent magnetohydrodynamic wave modes, both compressible and incompressible, in the solar chromosphere. The observed ubiquity and estimated energy flux associated with the detected magnetohydrodynamic waves suggest the chromosphere is a vast reservoir of wave energy with the potential to meet chromospheric and coronal heating requirements. We are also able to propose an upper bound on the flux of the observed wave energy that is able to reach the corona based on observational constraints, which has important implications for the suggested mechanism(s) for quiescent coronal heating. Title: Thin glass shell oriented to wide field x-ray telescope Authors: Civitani, M. M.; Citterio, O.; Campana, S.; Conconi, P.; Mattaini, E.; Pareschi, G.; Tagliaferri, G.; Parodi, G.; Burwitz, V.; Hartner, G. D.; Arnold, J.; Schuler, S.; Combrinck, H.; Freeman, R.; Morton, R.; Simpson, P.; Walker, D. Bibcode: 2012SPIE.8443E..0QC Altcode: The next generation wide-field X-ray telescope (WFXT), to be implemented beyond eRosita and proposed within the NASA RFI call 2011, requires an angular resolution of less than 10 arcsec (with goal of 5”) constant across a wide field of view (1 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. Bibcode: 2012cosp...39.1883S Altcode: 2012cosp.meet.1883S No abstract at ADS Title: Chromospheric jets around the edges of sunspots Authors: Morton, R. J. Bibcode: 2012A&A...543A...6M Altcode: 2012arXiv1205.2307M
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 http://www.aanda.org Title: Observations of quasi-periodic phenomena associated with a large blowout solar jet Authors: Morton, R. J.; Srivastava, A. K.; Erdélyi, R. Bibcode: 2012A&A...542A..70M Altcode: 2012arXiv1204.5033M
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 http://www.aanda.org Title: Transverse Oscillations in Chromospheric Mottles Authors: Kuridze, D.; Morton, R. J.; Erdélyi, R.; Dorrian, G. D.; Mathioudakis, M.; Jess, D. B.; Keenan, F. P. Bibcode: 2012ApJ...750...51K Altcode: 2012arXiv1202.5697K A number of recent investigations have revealed that transverse waves are ubiquitous in the solar chromosphere. The vast majority of these have been reported in limb spicules and active region fibrils. We investigate long-lived, quiet-Sun, on-disk features such as chromospheric mottles (jet-like features located at the boundaries of supergranular cells) and their transverse motions. The observations were obtained with the Rapid Oscillations in the Solar Atmosphere instrument at the Dunn Solar Telescope. The data set is comprised of simultaneous imaging in the Hα core, Ca II K, and G band of an on-disk quiet-Sun region. Time-distance techniques are used to study the characteristics of the transverse oscillations. We detect over 40 transverse oscillations in both bright and dark mottles, with periods ranging from 70 to 280 s, with the most frequent occurrence at ~165 s. The velocity amplitudes and transverse displacements exhibit characteristics similar to limb spicules. Neighboring mottles oscillating in-phase are also observed. The transverse oscillations of individual mottles are interpreted in terms of magnetohydrodynamic kink waves. Their estimated periods and damping times are consistent with phase mixing and resonant mode conversion. Title: Determination of Sub-resolution Structure of a Jet by Solar Magnetoseismology Authors: Morton, R. J.; Verth, G.; McLaughlin, J. A.; Erdélyi, R. Bibcode: 2012ApJ...744....5M Altcode: 2011arXiv1109.4851M A thin dark thread is observed in a UV/EUV solar jet in the 171 Å, 193 Å, and 211 Å, and partially in 304 Å. The dark thread appears to originate in the chromosphere but its temperature does not appear to lie within the passbands of the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory. We therefore implement solar magnetoseismology to estimate the plasma parameters of the dark thread. A propagating kink (transverse) wave is observed to travel along the dark thread. The wave is tracked over a range of ~7000 km by placing multiple slits along the axis of the dark thread. The phase speed and amplitude of the wave are estimated and magnetoseismological theory is employed to determine the plasma parameters. We are able to estimate the plasma temperature, density gradient, magnetic field gradient, and sub-resolution expansion of the dark thread. The dark thread is found to be cool, T <~ 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. Bibcode: 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. Bibcode: 2011SPIE.8147E..14C Altcode: 2011SPIE.8147E..37C The next generation wide-field X-ray telescope (WFXT) will require an angular resolution of ~5-10 arcsec almost constant across a wide field of view (~1 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. Bibcode: 2011SoPh..272...73E Altcode: 2010arXiv1011.2617E; 2011SoPh..tmp..314E; 2011SoPh..tmp..184E; 2011SoPh..tmp..253E; 2011SoPh..tmp..289E We investigate the propagation of MHD waves in a magnetised plasma in a weakly stratified atmosphere, representative of hot coronal loops. In most earlier studies, a time-independent equilibrium was considered. Here we abandon this restriction and allow the equilibrium to develop as a function of time. In particular, the background plasma is assumed to be cooling due to thermal conduction. The cooling is assumed to occur on a time scale greater than the characteristic travel times of the perturbations. We investigate the influence of cooling of the background plasma on the properties of magneto-acoustic waves. The MHD equations are reduced to a 1D system modelling magneto-acoustic modes propagating along a dynamically cooling coronal loop. A time-dependent dispersion relation that describes the propagation of the magneto-acoustic waves is derived using the WKB theory. An analytic solution for the time-dependent amplitude of waves is obtained, and the method of characteristics is used to find an approximate analytical solution. Numerical calculations of the analytically derived solutions are obtained to give further insight into the behaviour of the MHD waves in a system with a variable, time-dependent background. The results show that there is a strong damping of MHD waves and the damping also appears to be independent of the position along the loop. Studies of MHD wave behaviour in a time-dependent backgrounds seem to be a fundamental and very important next step in the development of MHD wave theory that is applicable to a wide range of situations in solar physics. Title: Kink and fluting modes of stratified coronal magnetic loops with elliptical cross-sections Authors: Morton, R. J.; Ruderman, M. S. Bibcode: 2011A&A...527A..53M Altcode: 2010arXiv1011.2377M
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. Bibcode: 2011ApJ...729L..18M Altcode: 2010arXiv1011.2375M We present here evidence for the observation of the magnetohydrodynamic (MHD) sausage modes in magnetic pores in the solar photosphere. Further evidence for the omnipresent nature of acoustic global modes is also found. The empirical decomposition method of wave analysis is used to identify the oscillations detected through a 4170 Å "blue continuum" filter observed with the Rapid Oscillations in the Solar Atmosphere (ROSA) instrument. Out of phase, periodic behavior in pore size and intensity is used as an indicator of the presence of magnetoacoustic sausage oscillations. Multiple signatures of the magnetoacoustic sausage mode are found in a number of pores. The periods range from as short as 30 s up to 450 s. A number of the magnetoacoustic sausage mode oscillations found have periods of 3 and 5 minutes, similar to the acoustic global modes of the solar interior. It is proposed that these global oscillations could be the driver of the sausage-type magnetoacoustic MHD wave modes in pores. Title: Application of the theory of damping of kink oscillations by radiative cooling of coronal loop plasma Authors: Morton, R. J.; Erdélyi, R. Bibcode: 2010A&A...519A..43M Altcode:
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 & 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. Bibcode: 2010SPIE.7732E..0DP Altcode: 2010SPIE.7732E..10P The Wide Field X-ray Telescope (WFXT) is a medium class mission for X-ray surveys of the sky with an unprecedented area and sensitivity. In order to meet the effective area requirement, the design of the optical system is based on very thin mirror shells, with thicknesses in the 1-2 mm range. In order to get the desired angular resolution (10 arcsec requirement, 5 arcsec goal) across the entire 1x1 degree FOV (Field Of View), the design of the optical system is based on nested modified grazing incidence Wolter-I mirrors realized with polynomial profiles, focal plane curvature and plate scale corrections. This design guarantees an increased angular resolution at large off-axis angle with respect to the normally used Wolter I configuration, making WFXT ideal for survey purposes. The WFXT X-ray Telescope Assembly is composed by three identical mirror modules of 78 nested shells each, with diameter up to 1.1 m. The epoxy replication process with SiC shells has already been proved to be a valuable technology to meet the angular resolution requirement of 10 arcsec. To further mature the telescope manufacturing technology and to achieve the goal of 5 arcsec, a deterministic direct polishing method is under investigation. The direct polishing method has already been used for past missions (as Einstein, Rosat, Chandra): the technological challenge now is to apply it for almost ten times thinner shells. Under investigation is quartz glass (fused silica), a well-known material with good thermo-mechanical and polishability characteristics that could meet our goal in terms of mass and stiffness, with significant cost and time saving with respect to SiC. Our approach is based on two main steps: first quartz glass tubes available on the market are grinded to conical profiles, and second the obtained shells are polished to the required polynomial profiles by CNC (Computer Numerical Control) polishing machine. In this paper, the first results of the direct grinding and polishing of prototypes shells made by quartz glass with low thickness, representative of the WFXT optical design, are presented. Title: Propagating magneto-hydrodynamic waves in a cooling homogenous coronal plasma Authors: Morton, R. J.; Hood, A. W.; Erdélyi, R. Bibcode: 2010A&A...512A..23M Altcode:
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. Bibcode: 2009ApJ...707..750M Altcode: Here we present an investigation into how cooling of the plasma influences the oscillation properties (e.g., eigenfunctions and eigenfrequencies) of transverse (i.e., kink) magnetohydrodynamic (MHD) waves in a compressible magnetic flux tube embedded in a gravitationally stratified and uniformly magnetized atmosphere. The cooling is introduced via a temperature-dependent density profile. A time-dependent governing equation is derived and an approximate zeroth-order solution is then obtained. From this the influence of cooling on the behavior of the eigenfrequencies and eigenfunctions of the transverse MHD waves is determined for representative cooling timescales. It is shown analytically, as the loop cools, how the amplitude of the perturbations is found to decrease as time increases. For cooling timescales of 900-2000 s (as observed in typical EUV loops), it is shown that the cooling has important and relevant influence on the damping times of loop oscillations. Next, the theory is put to the test. The damping due to cooling is fitted to a representative observation of standing kink oscillation of EUV loops. It is also shown with an explicit approximate analytical form, how the period of the fundamental and first harmonic of the kink mode changes with time as the loop cools. A consequence of this is that the value of the period ratio P 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. Bibcode: 2009A&A...502..315M Altcode: Aims: We determine the effect of an elliptical shape on the period ratio for the standing transversal oscillations of a longitudinally stratified coronal loop throughout its emergence from the low solar atmosphere into the ubiquitously magnetised corona.
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. Bibcode: 2009A&A...494..295E Altcode: Aims: The propagation of magnetohydrodynamic (MHD) waves in a finite, compressible magnetic flux tube with an elliptical cross-section embedded in a magnetic environment is investigated.
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. Bibcode: 2008SPIE.7018E..35B Altcode: 2008SPIE.7018E.100B This paper describes a major advance in the post-treatment of diamond-turned surfaces to remove repetitive micro-structure; a result which could have a major beneficial impact on fabrication of Walter-type X-ray mandrels, and metal mirrors. Diamond-turning is highly deterministic and versatile in producing axially-symmetric forms, and through fast-tool servos, non-axially symmetric, free-form and micro-structured surfaces. However, the fine turning marks left in the metal surface limit performance. In this paper, we describe how fluid-jet polishing under CNC control can be used to eliminate these structures, without significantly degrading the surface roughness or form produced by the prior turning operation. Title: Active control of edges and global microstructure on segmented mirrors Authors: Walker, D. D.; Beaucamp, A.; Dunn, C.; Evans, R.; Freeman, R.; Morton, R.; Wei, S.; Yu, G. Bibcode: 2008SPIE.7018E..12W Altcode: 2008SPIE.7018E..31W In this paper we address two interrelated issues important to primary mirror segments for extremely large telescopes - edge-control, and the detailed topography over the segment surface. Both affect the intensity and distribution of stray light and infrared emissivity. CNC polishing processes typically deploy spiral or raster tool-paths, tending to leave repetitive features. We compare and contrast two novel families of pseudo-random tool-paths for Precessions CNC polishing. We then show how CNC control of the three-dimensional tool-path can optimize edge-profiles. Finally, we demonstrate fluid-jet polishing used to clean up residual edge defects. Title: Automated optical fabrication: first results from the new Precessions 1.2m CNC polishing machine Authors: Walker, D. D.; Beaucamp, A. T. H.; Doubrovski, V.; Dunn, C.; Evans, R.; Freeman, R.; Kelchner, J.; McCavana, G.; Morton, R.; Riley, D.; Simms, J.; Yu, G.; Wei, X. Bibcode: 2006SPIE.6273E..09W Altcode: 2006SPIE.6273E...8W The requirements of space and defence optical systems and ground-based astronomy (especially extremely large telescopes) are providing optical fabricators with new challenges. These challenges particularly concern process speed, determinism and automation, and tighter tolerances on surface form and texture. Moreover, there is a growing demand for complex off-axis and 'freeform' surfaces and for larger components of the ~1m scale. With this in view, we first report on form-correction on a smaller analogue of the IRP1200: an IRP400 in service in industry. We then report on the design, commissioning and preliminary process-development results from the first of the scaled-up 1.2m capacity CNC polishing machine from Zeeko, Ltd. This machine delivers the 'Classic' bonnet-based process, together with two new processes: fluid-jet polishing and the hybrid soft-grinding/polishing process called 'Zeeko-Grolish.' We indicate how this trio of processes running on the same machine platform with unified software can provide an unprecedented dynamic range in both volumetric removal rate and removal spot-size. This leads into a discussion of how these processes may be brought to bear on optimal control of texture and form. Preliminary performance of the 1.2m machine is illustrated with results on both axially-symmetric and more complex removal regimes. The paper concludes with an overview of the relevance of the technology to efficient production of instrumentation-optics, space optics and segmented telescope mirrors. Title: Recent advances in the control of form and texture on free-form surfaces Authors: Walker, D. D.; Beaucamp, A. T.; Doubrovski, V.; Dunn, C.; Freeman, R.; Hobbs, G.; McCavana, G.; Morton, R.; Riley, D.; Simms, J.; Wei, X. Bibcode: 2005SPIE.5965..249W Altcode: The recent upsurge in the demand for off-axis and complex "freeform" optical surfaces is driving the development of novel processes for their fabrication. This paper focuses on recent developments of the Precessions CNC polishing process for freeform surfaces, including off-axis as a special case. First, the surface-prescription and metrology-data, and their relation to the data-input for the polishing machines, are considered. The relevance of consistent coordinate frames is emphasised. An outline of how the process can 'polish' a ground freeform part (improve the texture), and then 'figure' the part (reduce the form errors) is given. Specific experimental case-studies are then presented, illustrating the versatility of the process on different materials and forms. Recent work is included in which the process-speed has been moderated in order to remove tens of nanometres of stock material, rather then the more usual hundreds of nanometres to tens of microns as in the standard Precessions process. The relevance of this to improving the ultimate surface-precision that should be achievable by this method is described. As a final illustration, the potential of the process to the rapid fabrication of the hundreds to thousands of 1-2 metre class mirror segments required for extremely large telescopes is considered. Title: New results extending the Precessions process to smoothing ground aspheres and producing freeform parts Authors: Walker, D. D.; Beaucamp, A. T. H.; Doubrovski, V.; Dunn, C.; Freeman, R.; McCavana, G.; Morton, R.; Riley, D.; Simms, J.; Wei, X. Bibcode: 2005SPIE.5869...79W Altcode: Zeeko's Precession polishing process uses a bulged, rotating membrane tool, creating a contact-area of variable size. In separate modes of operation, the bonnet rotation-axis is orientated pole-down on the surface, or inclined at an angle and then precessed about the local normal. The bonnet, covered with standard polishing cloth and working with standard slurry, has been found to give superb surface textures in the regime of nanometre to sub-nanometre Ra values, starting with parts directly off precision CNC aspheric grinding machines. This paper reports an important extension of the process to the precision-controlled smoothing (or 'fining') operation required between more conventional diamond milling and subsequent Precession polishing. The method utilises an aggressive surface on the bonnet, again with slurry. This is compared with an alternative approach using diamond abrasives bound onto flexible carriers attached to the bonnets. The results demonstrate the viability of smoothing aspheric surfaces, which extends Precessions processing to parts with inferior input-quality. This may prove of particular importance to large optics where significant volumes of material may need to be removed, and to the creation of more substantial aspheric departures from a parent sphere. The paper continues with a recent update on results obtained, and lessons learnt, processing free-form surfaces, and concludes with an assessment of the relevance of the smoothing and free-form operations to the fabrication of off-axis parts including segments for extremely large telescopes. Title: Kinetics of suprathermal hydrogen atom reactions with saturated hydrides in planetary and satellite atmospheres Authors: Morton, Richard J.; Kaiser, Ralf I. Bibcode: 2003P&SS...51..365M Altcode: The kinetics of saturated hydrides methane (CH 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. Bibcode: 1985Natur.314..688J Altcode: No abstract at ADS Title: The statistical analysis and interpretation of imperfectly-fitted Rb-Sr isochrons from polymetamorphic terrains (reply to a comment by H. Austrheim) Authors: Cameron, M.; Collerson, K. D.; Compston, W.; Morton, R. Bibcode: 1983GeCoA..47..659C Altcode: No abstract at ADS Title: The statistical analysis and interpretation of imperfectly-fitted Rb-Sr isochrons from polymetamorphic terrains Authors: Cameron, M.; Collerson, K. D.; Compston, W.; Morton, R. Bibcode: 1981GeCoA..45.1087C Altcode: Rb-Sr isotopic data for large, relatively homogeneous, whole-rock samples of Uivak 1 gneiss from the Saglek-Hebron area of northern Labrador exhibit a scatter which exceeds that predicted by experimental error. Isotopic analyses of adjacent compositionally-different layers of Uivak gneiss, 1-2 cm in width, define secondary isochrons, with slopes corresponding to an age of ca. 1800 Ma. As field evidence combined with previous isotopic dating demonstrates that the compositional layering did not form at this time, the secondary isochrons are interpreted as resulting from localized Sr-isotopic homogenization along 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