Observational Constraints on Coronal Heating Models Using Coronal Diagnostics Spectrometer and Soft X‐Ray Telescope Data

Schmelz, J. T.; Scopes, R. T.; Cirtain, Jonathan; Winter, H. D.; Allen, J. D.

doi:10.1086/321588

Cited by 106 publications

(109 citation statements)

References 28 publications

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“…Recently, TRACE data on the ratio between two well chosen spectral lines observed nearly simultaneously have been used to derive temperature profiles along loops (Aschwanden et al 1999). On the other hand, Schmelz et al (2001) reported problems with this approach and appealed that more advanced methods are required for getting reliable temperature estimates for coronal plasmas. Ideally speaking, the combination of such observational results with a family of reconnection solutions could help us better understand the functional behaviour of magnetised plasma in which the reconnection process takes place.…”

Section: Summary and Future Workmentioning

confidence: 99%

Magnetic reconnection in 2D stratified atmospheres

Galsgaard¹,

Roussev

2002

A&A

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Abstract.We explore the dynamical consequences of magnetic reconnection in a 2D stratified physical configuration representing a "quiet" solar environment. By including gravity, an initial magneto-hydrostatic solution is found that allows the magnetic field to expand with height. The change in kinetic gas pressure with height leads to the formation of a cold current "sheet" in the case of strong stratification, in contrast to a hot current "sheet" in the case of negligible stratification. Here the "sheet" temperature is measured relative to the temperature in the ambient background plasma. The dynamics of magnetic reconnection in a stratified atmosphere evolves through a new initial stage, with a more complex velocity structure than the quadrupolar velocity pattern present in traditional 2D X-point reconnection. As time progresses, the new initial phase is suppressed and the driven reconnection evolves into the traditional 2D reconnection pattern. The transition time between the two regimes is found to depend on the imposed stratification, and through this, on the degree of expansion of the initial magnetic field with height. The new reconnection regime undergoes a more complicated physical evolution and seems to have a lower reconnection rate than the classical 2D X-point reconnection. The faster the magnetic field expands with height, the slower and more complex are the dynamics of the magnetic reconnection at the early stages of its evolution.

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Section: Summary and Future Workmentioning

confidence: 99%

Magnetic reconnection in 2D stratified atmospheres

Galsgaard¹,

Roussev

2002

A&A

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“…Schmelz & Martens (2006) applied various backgroundsubtraction methods to previously analyzed data (see Schmelz et al 2001 for previous results) and found that although the DEM curves determined from background subtracted pixels were reduced in temperature coverage, the results were conclusive: the postflare coronal loops observed were not isothermal. It could, however, be that quiescent active region loops are heated differently from postflare loops.…”

Section: Introductionmentioning

confidence: 99%

“…It has been suggested that the discrepancy between the temperatures resulting from DEMs, such as those from Schmelz et al (2001) and the narrowband filter ratio results of Winebarger et al (2003) could be due to specious background subtraction methods. Schmelz & Martens (2006) applied various backgroundsubtraction methods to previously analyzed data (see Schmelz et al 2001 for previous results) and found that although the DEM curves determined from background subtracted pixels were reduced in temperature coverage, the results were conclusive: the postflare coronal loops observed were not isothermal.…”

Section: Introductionmentioning

confidence: 99%

Active Region Loops: Temperature Measurements as a Function of Time from JointTRACEandSOHOCDS Observations

Cirtain

Zanna

DeLuca

et al. 2007

ApJ

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In this paper, we aim to quantitatively investigate the structure and time variation of quiescent active region loop structures. We coordinated a joint program of observations (JOP 146) using TRACE, to obtain high-cadence EUV images, and SOHO CDS, to obtain spectroscopic data. Loop intensities are used to determine temperature as a function of time for a single loop, taking full account of the background emission. In many locations, the emission measure loci are consistent with an isothermal structure. However, the results indicate significant changes in the loop temperature (between 1 and 2 MK) over the 6 hr observing period. It is possible that the loop structures are composed of multiple, independently heated strands with sizes less than the resolution of the imager and spectrometer.

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“…Similarly, coronal loops may have non-circular cross-section (Ruderman 2003). Furthermore, there is good evidence that loops have substructure, consisting of elemental magnetic flux strands of widths less than 2 Mm (Schmelz et al 2001(Schmelz et al , 2003(Schmelz et al , 2005Schmelz 2002;Martens et al 2002;Aschwanden & Nightingale 2005;Aschwanden 2005). …”

Section: Introductionmentioning

confidence: 99%

Resonant absorption with 2D variation of field line eigenfrequencies

Russell

Wright

2010

A&A

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Context. Resonant absorption, also known as field line resonance, can be used to describe coupling between fast and Alfvén waves in non-uniform plasmas. Since the conditions for resonant absorption occur widely in astrophysics, it is applicable in many different contexts, all of which are united by their common physics. For example, resonant absorption is known to play a major role in the excitation of ultra-low frequency pulsations in the terrestrial magnetosphere and is also a leading explanation for the decay of fast kink oscillations of coronal loops. The occurrence of non-axisymmetric conditions in the magnetosphere, and observational evidence that coronal loops may possess fine transverse structure, highlight a need to consider equilibria that vary in two dimensions across the background magnetic field. Aims. We investigate the properties of resonant absorption when field line eigenfrequencies vary in two dimensions across the background magnetic field. We aim to place the theory on a firm mathematical footing and explore some of its key features. Methods. Using cold, linear, ideal MHD with a straight, uniform background magnetic field, we systematically obtain a complete analytic solution for behaviour at late times. This provides a framework from which the features of resonant absorption may be understood. The time-dependent problem is solved numerically, reproducing key features of the analytic solution. Results. Energy is deposited from a monochromatic fast wave as a phase mixing Alfvén wave, in the vicinity of the resonant surface, at which the local field line eigenfrequency matches the frequency of the driver. A generalisation of the one dimensional phase mixing length to higher dimensions is suggested, and shown to successfully estimate the finest lengthscales in time-dependent simulations. The resonant Alfvén wave is driven by gradients of the field aligned magnetic field perturbation, which is associated with the fast wave pressure. This leads to amplitude variations of the Alfvén wave that can be used to reveal the spatial form of the fast wave.

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Observational Constraints on Coronal Heating Models Using Coronal Diagnostics Spectrometer and Soft X‐Ray Telescope Data

Cited by 106 publications

References 28 publications

Magnetic reconnection in 2D stratified atmospheres

Magnetic reconnection in 2D stratified atmospheres

Active Region Loops: Temperature Measurements as a Function of Time from JointTRACEandSOHOCDS Observations

Resonant absorption with 2D variation of field line eigenfrequencies

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