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Title: ULTRAVIOLET AND EXTREME-ULTRAVIOLET EMISSIONS AT THE FLARE FOOTPOINTS OBSERVED BY ATMOSPHERE IMAGING ASSEMBLY

A solar flare is composed of impulsive energy release events by magnetic reconnection, which forms and heats flare loops. Recent studies have revealed a two-phase evolution pattern of UV 1600 A emission at the feet of these loops: a rapid pulse lasting for a few seconds to a few minutes, followed by a gradual decay on timescales of a few tens of minutes. Multiple band EUV observations by the Atmosphere Imaging Assembly further reveal very similar signatures. These two phases represent different but related signatures of an impulsive energy release in the corona. The rapid pulse is an immediate response of the lower atmosphere to an intense thermal conduction flux resulting from the sudden heating of the corona to high temperatures (we rule out energetic particles due to a lack of significant hard X-ray emission). The gradual phase is associated with the cooling of hot plasma that has been evaporated into the corona. The observed footpoint emission is again powered by thermal conduction (and enthalpy), but now during a period when approximate steady-state conditions are established in the loop. UV and EUV light curves of individual pixels may therefore be separated into contributions from two distinct physical mechanisms to shedmore » light on the nature of energy transport in a flare. We demonstrate this technique using coordinated, spatially resolved observations of UV and EUV emissions from the footpoints of a C3.2 thermal flare.« less
Authors:
; ;  [1] ;  [2] ;  [3]
  1. Department of Physics, Montana State University, Bozeman, MT 59717-3840 (United States)
  2. Department of Applied Mathematics, University of St. Andrews (United Kingdom)
  3. NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
Publication Date:
OSTI Identifier:
22133987
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 774; 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; COOLING; EARTH ATMOSPHERE; EMISSION; ENTHALPY; EVOLUTION; EXTREME ULTRAVIOLET RADIATION; HARD X RADIATION; HEATING; HOT PLASMA; MAGNETIC RECONNECTION; SOLAR CORONA; SOLAR FLARES; STEADY-STATE CONDITIONS; TEMPERATURE RANGE 0400-1000 K; THERMAL CONDUCTION