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Title: ON THE CAUSE OF SUPRA-ARCADE DOWNFLOWS IN SOLAR FLARES

A model of supra-arcade downflows (SADs), dark low density regions also known as tadpoles that propagate sunward during solar flares, is presented. It is argued that the regions of low density are flow channels carved by sunward-directed outflow jets from reconnection. The solar corona is stratified, so the flare site is populated by a lower density plasma than that in the underlying arcade. As the jets penetrate the arcade, they carve out regions of depleted plasma density which appear as SADs. The present interpretation differs from previous models in that reconnection is localized in space but not in time. Reconnection is continuous in time to explain why SADs are not filled in from behind as they would if they were caused by isolated descending flux tubes or the wakes behind them due to temporally bursty reconnection. Reconnection is localized in space because outflow jets in standard two-dimensional reconnection models expand in the normal (inflow) direction with distance from the reconnection site, which would not produce thin SADs as seen in observations. On the contrary, outflow jets in spatially localized three-dimensional reconnection with an out-of-plane (guide) magnetic field expand primarily in the out-of-plane direction and remain collimated in the normal direction,more » which is consistent with observed SADs being thin. Two-dimensional proof-of-principle simulations of reconnection with an out-of-plane (guide) magnetic field confirm the creation of SAD-like depletion regions and the necessity of density stratification. Three-dimensional simulations confirm that localized reconnection remains collimated.« less
Authors:
;  [1] ;  [2] ;  [3] ;  [4] ;  [5]
  1. Department of Physics and Astronomy, West Virginia University, Morgantown, WV 26506 (United States)
  2. Department of Physics and the Institute for Physical Science and Technology and the Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, MD 20742 (United States)
  3. Laboratory for Atmospheric and Space Physics, University of Colorado at Boulder, Boulder, CO 80303 (United States)
  4. Space Science Laboratory, University of California, Berkeley, CA 94720 (United States)
  5. Department of Physics and Astronomy, University of Delaware, Newark, DE 20742 (United States)
Publication Date:
OSTI Identifier:
22215468
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 775; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; DENSITY; DISTANCE; MAGNETIC FIELDS; MAGNETIC RECONNECTION; PLASMA DENSITY; SIMULATION; SOLAR CORONA; SOLAR FLARES; SPACE; STRATIFICATION; SUN