Peristaltic Pumping Near Post-Coronal Mass Ejection Supra-Arcade Current Sheets

Scott, Roger B.; Longcope, D. W.; McKenzie, D. E.

doi:10.1088/0004-637x/776/1/54

Cited by 24 publications

(34 citation statements)

References 28 publications

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“…We also note that the last two narrow SADs simply slowed down and faded in the bright fan plasma. There was no indication of either a loop or enhanced emission at their heads, as has been predicted by some retracting loop models (Scott et al 2013). …”

Section: Km Ssupporting

confidence: 59%

“…When the loops descend through the supra-arcade fan, they may drive shocks ahead and rarefactions behind (Scott et al 2013) travelling with speeds of the order of the local sound speed (350 km s −1 for 10 MK plasma). The SAD model developed by Costa et al (2009), Maglione et al (2011), and Cécere et al (2012 assumes multiple reconnection sites in which the SADs are a consequence of shocks and rarefactions bouncing back and forth in magnetic structures.…”

Section: Introductionmentioning

confidence: 99%

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Observations of Supra-Arcade Fans: Instabilities at the Head of Reconnection Jets

Innes¹,

Guo²,

Bhattacharjee³

et al. 2014

ApJ

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Supra-arcade fans are bright, irregular regions of emission that develop during eruptive flares, above flare arcades. The underlying flare arcades are thought to be a consequence of magnetic reconnection along a current sheet in the corona. At the same time, theory predicts plasma jets from the reconnection site which would be extremely difficult to observe directly becuase of their low density. It has been suggested that the dark supra-arcade downflows (SADs) seen falling through supra-arcade fans may be low density jet plasma. The head of a low density jet directed towards higher density plasma would be Rayleigh-Taylor unstable, and lead to the development of rapidly growing low and high density fingers along the interface. Using SDO/AIA 131Å images, we show details of SADs seen from three different orientations with respect to the flare arcade and current sheet, and highlight features that have been previously unexplained, such as the splitting of SADs at their heads, but are a natural consequence of instabilities above the arcade. Comparison with 3-D magnetohydrodynamic simulations suggests that supra-arcade downflows are the result of secondary instabilities of the Rayleigh-Taylor type in the exhaust of reconnection jets.

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Section: Km Ssupporting

confidence: 59%

Section: Introductionmentioning

confidence: 99%

Observations of Supra-Arcade Fans: Instabilities at the Head of Reconnection Jets

Innes¹,

Guo²,

Bhattacharjee³

et al. 2014

ApJ

View full text Add to dashboard Cite

show abstract

“…This value has been employed in a number of numerical simulations of late (Cécere et al 2012(Cécere et al , 2015Guo et al 2014). Our own more recent work (Scott 2016) extends the efforts of Scott et al (2013), showing that these results are also valid for β1. In the coming years it will be important, therefore, to test each of these models against different β regimes; only in this way will we ever be able to truly pinpoint the energy distribution of the supra-arcade region and, simultaneously, explain the fundamental processes behind the evolution of supra-arcade features.…”

supporting

confidence: 55%

Inferring the Magnetohydrodynamic Structure of Solar Flare Supra-Arcade Plasmas From a Data-Assimilated Field Transport Model

Scott

McKenzie

Longcope

2016

ApJ

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Supra-arcade fans are highly dynamic structures that form in the region above post-reconnection flare arcades. In these features the plasma density and temperature evolve on the scale of a few seconds, despite the much slower dynamics of the underlying arcade. Further, the motion of supra-arcade plasma plumes appears to be inconsistent with the low-beta conditions that are often assumed to exist in the solar corona. In order to understand the nature of these highly debated structures,it is, therefore, important to investigate the interplay of the magnetic field with the plasma. Here we present a technique for inferring the underlying magnetohydrodynamic processes that might lead to the types of motions seen in supra-arcade structures. Taking as a case study the 2011 October 22 event, we begin with extreme-ultraviolet observations and develop a time-dependent velocity field that is consistent with both continuity and local correlation tracking. We then assimilate this velocity field into a simplified magnetohydrodynamic simulation, which deals simultaneously with regions of high and low signal-to-noise ratio, thereby allowing the magnetic field to evolve self-consistently with the fluid. Ultimately, we extract the missing contributions from the momentum equation in order to estimate the relative strength of the various forcing terms. In this way we are able to make estimates of the plasma beta, as well as predictthe spectral character and total power of Alfvén waves radiated from the supra-arcade region.

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“…It is possible that flux within the current sheet has experienced some heating and "densification" prior to its actual reconnection (Scott et al 2013, offers one possible mechanism). Another possibility is that reconnection of other flux, during the preceding phase of the same flare, might have supplied energy across field lines and driven evaporation into that flux tube.…”

Section: Discussionmentioning

confidence: 99%

A Reconnection-Driven Model of the Hard X-Ray Loop-Top Source From Flare 2004 February 26

Longcope

Qiu

Brewer

2016

ApJ

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A reconnection-driven model of the hard X-ray loop-top source from flare 2004-Feb-26 Dana Longcope 1 , Jiong Qiu 1 , and Jasmine Brewer ABSTRACT A compact X-class flare on 2004-Feb-26 showed a concentrated source of hard X-rays at the tops of the flare's loops. This was analyzed in previous work , and interpreted as plasma heated and compressed by slow magnetosonic shocks generated during post-reconnection retraction of the flux. That work used analytic expressions from a thin flux tube (TFT) model, which neglected many potentially important factors such as thermal conduction and chromospheric evaporation. Here we use a numerical solution of the TFT equations to produce a more comprehensive and accurate model of the same flare, including those effects previously omitted. These simulations corroborate the prior hypothesis that slow mode shocks persist well after the retraction has ended, thus producing a compact, loop-top source instead of an elongated jet, as steady reconnection models predict. Thermal conduction leads to densities higher than analytic estimates had predicted, and evaporation enhances the density still higher, but at lower temperatures. X-ray light curves and spectra are synthesized by convolving the results from a single TFT simulation with the rate at which flux is reconnected, as measured through motion of flare ribbons, for example. These agree well with light curves observed by RHESSI and GOES and spectra from RHESSI. An image created from a superposition of TFT model runs resembles one produced from RHESSI observations. This suggests that the HXR looptop source, at least the one observed in this flare, could be the result of slow magnetosonic shocks produced in fast reconnection models like Petschek's.

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Peristaltic Pumping Near Post-Coronal Mass Ejection Supra-Arcade Current Sheets

Cited by 24 publications

References 28 publications

Observations of Supra-Arcade Fans: Instabilities at the Head of Reconnection Jets

Observations of Supra-Arcade Fans: Instabilities at the Head of Reconnection Jets

Inferring the Magnetohydrodynamic Structure of Solar Flare Supra-Arcade Plasmas From a Data-Assimilated Field Transport Model

A Reconnection-Driven Model of the Hard X-Ray Loop-Top Source From Flare 2004 February 26

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