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Title: PLASMA HEATING IN A POST ERUPTION CURRENT SHEET: A CASE STUDY BASED ON ULTRAVIOLET, SOFT, AND HARD X-RAY DATA

Off-limb observations of the solar corona after coronal mass ejections (CMEs) often show strong, compact, and persistent UV sources behind the eruption. They are primarily observed by the SOHO/UVCS instrument in the 'hot' [Fe XVIII] λ974 line and are usually interpreted as a signature of plasma heating due to magnetic reconnection in the post-CME current sheet (CS). Nevertheless, the physical process itself and the altitude of the main energy release are currently not fully understood. In this work, we study the evolution of plasma heating after the CME of 2004 July 28 by comparing UV spectra acquired by UVCS with soft and hard X-ray (SXR, HXR) images of the post-flare loops taken by GOES/SXI and RHESSI. The X-ray data show a long-lasting extended source that is rising upward, toward the high-temperature source detected by UVCS. UVCS data show the presence of significant non-thermal broadening in the CS (a signature of turbulent motions) and a strong density gradient across the CS region. The thermal energy released in the HXR source is on the order of ∼10{sup 32} erg, a factor ∼2-5 larger than the energy required to explain the high-temperature plasma sampled by UVCS. Nevertheless, the very different time evolutions ofmore » SXR and HXR sources compared with the UV emission suggest that reconnection occurring above the post-eruption arcades is not directly responsible for the high-temperature plasma sampled higher up by UVCS. We conclude that an additional plasma heating mechanism (such as turbulent reconnection) in the CS is likely required.« less
Authors:
;  [1] ;  [2]
  1. INAF - Osservatorio Astrofisico di Torino, via Osservatorio 20, I-10025 Pino Torinese (Italy)
  2. University of Applied Sciences and Arts Northwestern Switzerland, CH-5210 Windisch (Switzerland)
Publication Date:
OSTI Identifier:
22270615
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 777; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTRONOMY; ASTROPHYSICS; COMPARATIVE EVALUATIONS; GAMMA RADIATION; HARD X RADIATION; HOT PLASMA; IRON IONS; MAGNETIC RECONNECTION; PLASMA HEATING; SOLAR CORONA; SUN; TURBULENCE; ULTRAVIOLET RADIATION; ULTRAVIOLET SPECTRA