An Exploration of Heating Mechanisms in a Supra-arcade Plasma Sheet Formed after a Coronal Mass Ejection

Reeves, Katharine K.; Freed, Michael; McKenzie, D. E.; Savage, Sabrina

doi:10.3847/1538-4357/836/1/55

Cited by 47 publications

(62 citation statements)

References 41 publications

(58 reference statements)

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“…12 and 32. In the event of 2011 October 22, observed from the face-on perspective, Reeves et al (2017) found temperature peaking in an elongated ridge lying just above the arcade. They observed SADs occurring above it and even passing through it.…”

Section: Downflows In the Plasma Sheetmentioning

confidence: 93%

“…When an eruption is viewed face-on, its trailing plasma sheet appears as a tall, broad, fan-like structure above the post-flare arcade (Švestka et al 1998), offering complimentary insight. Of particular note are elongated dark structures, called supraarcade downflows (SADs), observed to move sunward through the plasma sheet (McKenzie & Hudson 1999;Innes et al 2003;Sheeley et al 2004;Khan et al 2007;McKenzie & Savage 2009;Savage & McKenzie 2011;Guo et al 2013;Reeves et al 2017). Supra-arcade fans viewed edge-on sometimes exhibit downward-moving loops, called supra-arcade downflowing loops (SADLs) interpreted as SADs viewed from a different perspective (Savage & McKenzie 2011).…”

Section: Introductionmentioning

confidence: 99%

“…In any case the downflowing features reveal the motion of reconnected flux tubes. Their motion, as well as the motion of the surrounding plasma, has revealed that the sheet is at relatively high plasma β (McKenzie 2013; Scott et al 2016b) and may be heated by its own compression (Reeves et al 2017).…”

Section: Introductionmentioning

confidence: 99%

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Evidence for Downflows in the Narrow Plasma Sheet of 2017 September 10 and Their Significance for Flare Reconnection

Longcope

Unverferth

Klein

et al. 2018

ApJ

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Current sheets are believed to form in the wakes of erupting flux ropes and to enable the magnetic reconnection responsible for an associated flare. Multiwavelength observations of an eruption on 2017 September 10 show a long, linear feature widely taken as evidence of a current sheet viewed edge-on. The relation between the hightemperature, high-density plasma thus observed and any current sheet is not yet entirely clear. We estimate the magnetic field strength surrounding the sheet and conclude that approximately one-third of all flux in the active region was opened by the eruption. Subsequently decreasing field strength suggests that the open flux closed down over the next several hours through reconnection at a rate F 5 10 17 Mx s −1. We find in AIA observations evidence of downward-moving, dark structures analogous to either supra-arcade downflows, more typically observed above flare arcades viewed face-on, or supra-arcade downflowing loops, previously reported in flares viewed in this perspective. These features suggest that the plasma sheet is composed of the magnetic flux retracting after being reconnected high above the arcade. We model flux tube retraction following reconnection to show that this process can generate high densities and temperatures as observed in the plasma sheet. The retracting flux tubes reach their highest temperatures at the end of their retraction, well below the site of reconnection, consistent with previous analysis of AIA and EIS data showing a peak in the plasma temperature near the base of this particular sheet.

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Section: Downflows In the Plasma Sheetmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Evidence for Downflows in the Narrow Plasma Sheet of 2017 September 10 and Their Significance for Flare Reconnection

Longcope

Unverferth

Klein

et al. 2018

ApJ

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“…These structures persist for long times in the late phase of an eruption (e.g. Hanneman & Reeves 2014;Savage et al 2012), lasting much longer arXiv:1910.05386v1 [astro-ph.SR] 11 Oct 2019 than the conductive cooling time (Reeves et al 2017). This finding indicates that there must either be some heating mechanism in the vicinity of the current sheet that keeps the plasma from cooling, or a suppression of the thermal conduction in this region (or both).…”

Section: Introductionmentioning

confidence: 99%

Exploring Plasma Heating in the Current Sheet Region in a Three-dimensional Coronal Mass Ejection Simulation

Reeves

Török

Mikić

et al. 2019

ApJ

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We simulate a coronal mass ejection (CME) using a three-dimensional magnetohydrodynamic (MHD) code that includes coronal heating, thermal conduction, and radiative cooling in the energy equation. The magnetic flux distribution at 1 R s is produced by a localized subsurface dipole superimposed on a global dipole field, mimicking the presence of an active region within the global corona. Transverse electric fields are applied near the polarity inversion line to introduce a transverse magnetic field, followed by the imposition of a converging flow to form and destabilize a flux rope, producing an eruption. We examine the quantities responsible for plasma heating and cooling during the eruption, including thermal conduction, radiation, adiabatic effects, coronal heating, and ohmic heating. We find that ohmic heating is an important contributor to hot temperatures in the current sheet region early in the eruption, but in the late phase adiabatic compression plays an important role in heating the plasma there. Thermal conduction also plays an important role in the transport of thermal energy away from the current sheet region throughout the reconnection process, producing a "thermal halo" and widening the region of high temperatures. We simulate emission from solar telescopes for this eruption and find that there is evidence for emission from heated plasma above the flare loops late in the eruption, when the adiabatic heating is the dominant heating term. These results provide an explanation for hot supra-arcade plasma sheets that are often observed in X-rays and extreme ultraviolet wavelengths during the decay phase of large flares.

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“…Recent high temporal and spatial resolution measurements make the detailed analysis of erupting solar coronal plasma possible. Most coronal analyses assume ionization equilibrium to determine the physical properties of the erupting plasma (Cheng et al 2012;Hannah & Kontar 2013;Patsourakos et al 2013;Tripathi et al 2013;Hanneman & Reeves 2014;Lee et al 2015Lee et al , 2017Reeves et al 2017). In ionization equilibrium, the responses of the Atmospheric Imaging Assembly (AIA) on board Solar Dynamic Observatory and X-ray Telescope (XRT) on board Hinode are functions of temperature alone.…”

Section: Introductionmentioning

confidence: 99%

Nonequilibrium Ionization Effects on Solar EUV and X-Ray Imaging Observations

Lee

Raymond

Reeves

et al. 2019

ApJ

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During transient events such as major solar eruptions, the plasma can be far from the equilibrium ionization state because of rapid heating or cooling. Non-equilibrium ionization (NEI) is important in rapidly evolving systems where the thermodynamical timescale is shorter than the ionization or recombination time scales. We investigate the effects of NEI on EUV and X-ray observations by the Atmospheric Imaging Assembly (AIA) on board Solar Dynamic Observatory and X-ray Telescope (XRT) on board Hinode. Our model assumes that the plasma is initially in ionization equilibrium at low temperature, and it is heated rapidly by a shock or magnetic reconnection. We tabulate the responses of the AIA and XRT passbands as functions of temperature and a characteristic timescale, n e t. We find that most of the ions reach equilibrium at n e t ≤10 12 cm −3 s. Comparing ratios of the responses between different passbands allows us to determine whether a combination of plasmas at temperatures in ionization equilibrium can account for a given AIA and XRT observation. It also expresses how far the observed plasma is from equilibrium ionization. We apply the ratios to a supraarcade plasma sheet on 2012 January 27. We find that the closer the plasma is to the arcade, the closer it is to a single-temperature plasma in ionization equilibrium. We also utilize the set of responses to estimate the temperature and density for shocked plasma associated with a coronal mass ejection on 2010 June 13. The temperature and density ranges we obtain are in reasonable agreement with previous works.

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An Exploration of Heating Mechanisms in a Supra-arcade Plasma Sheet Formed after a Coronal Mass Ejection

Cited by 47 publications

References 41 publications

Evidence for Downflows in the Narrow Plasma Sheet of 2017 September 10 and Their Significance for Flare Reconnection

Evidence for Downflows in the Narrow Plasma Sheet of 2017 September 10 and Their Significance for Flare Reconnection

Exploring Plasma Heating in the Current Sheet Region in a Three-dimensional Coronal Mass Ejection Simulation

Nonequilibrium Ionization Effects on Solar EUV and X-Ray Imaging Observations

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