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Title: Where is the chromospheric response to conductive energy input from a hot pre-flare coronal loop?

Before the onset of a flare is observed in hard X-rays, there is often a prolonged pre-flare or pre-heating phase with no detectable hard X-ray emission but pronounced soft X-ray emission, which suggests that energy is already being released and deposited into the corona and chromosphere at this stage. This work analyzes the temporal evolution of coronal source heating and the chromospheric response during this pre-heating phase to investigate the origin and nature of early energy release and transport during a solar flare. Simultaneous X-ray, EUV, and microwave observations of a well-observed flare with a prolonged pre-heating phase are analyzed to study the time evolution of the thermal emission and to determine the onset of particle acceleration. During the 20 minute duration of the pre-heating phase we find no hint of accelerated electrons in either hard X-rays or microwave emission. However, the total energy budget during the pre-heating phase suggests that energy must be supplied to the flaring loop to sustain the observed temperature and emission measure. Under the assumption of this energy being transported toward the chromosphere via thermal conduction, significant energy deposition at the chromosphere is expected. However, no detectable increase of the emission in the AIA wavelengthmore » channels sensitive to chromospheric temperatures is observed. The observations suggest energy release and deposition in the flaring loop before the onset of particle acceleration, yet a model in which energy is conducted to the chromosphere and subsequent heating of the chromosphere is not supported by the observations.« less
Authors:
 [1] ; ;  [2]
  1. Institute of 4D Technologies, School of Engineering, University of Applied Sciences and Arts Northwestern Switzerland, CH-5210 Windisch (Switzerland)
  2. SUPA School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom)
Publication Date:
OSTI Identifier:
22356483
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 789; 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; ACCELERATION; CHROMOSPHERE; DEPOSITION; ECOSYSTEMS; ELECTRONS; EMISSION; ENERGY ABSORPTION; ENERGY BALANCE; ENERGY LOSSES; EXTREME ULTRAVIOLET RADIATION; GAMMA RADIATION; HARD X RADIATION; MICROWAVE RADIATION; PARTICLES; SOFT X RADIATION; SOLAR FLARES; SUN; ULTRAVIOLET RADIATION; WAVELENGTHS