Direct observation of the energy release site in a solar flare by SDO/AIA, Hinode/EIS and RHESSI

Simoes, P.J.A. , Graham, D.R. and Fletcher, L. (2015) Direct observation of the energy release site in a solar flare by SDO/AIA, Hinode/EIS and RHESSI. Astronomy and Astrophysics, 577, A68. (doi: 10.1051/0004-6361/201424795)

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We present direct evidence for the detection of the main energy release site in a non-eruptive solar flare, SOL2013-11-09T06:38UT. This GOES C2.7 event was characterised by two flaring ribbons and a compact, bright coronal source located between them, which is the focus of our study. We use imaging from SDO/AIA, and imaging spectroscopy from RHESSI to characterise the thermal and non-thermal emission from the coronal source, and EUV spectroscopy from the Hinode/EIS, which scanned the coronal source during the impulsive peak, to analyse Doppler shifts in Fe XII and Fe XXIV emission lines, and determine the source density. The coronal source exhibited an impulsive emission lightcurve in all AIA filters during the impulsive phase. RHESSI hard X-ray images indicate both thermal and non-thermal emission at the coronal source, and its plasma temperature derived from RHESSI imaging spectroscopy shows an impulsive rise, reaching a maximum at 12-13 MK about 10 seconds prior to the hard X-ray peak. High redshifts associated with this bright source indicate downflows of 40-250 km/s at a broad range of temperatures, interpreted as loop shrinkage and/or outflows along the magnetic field. Outflows from the coronal source towards each ribbon are also observed by AIA images at 171, 193, 211, 304 and 1600 A. The electron density of the source obtained from a Fe XIV line pair is 1011.50 which is collisionally thick to electrons with energy up to 45-65 keV, responsible for the source's non-thermal X-ray emission. We conclude that the bright coronal source is the location of the main release of magnetic energy in this flare, with a geometry consistent with component reconnection between crossing, current-carrying loops. We argue that the energy that can be released via reconnection, based on observational estimates, can plausibly account for the non-thermal energetics of the flare.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Graham, Mr David and Simoes, Dr Paulo and Fletcher, Professor Lyndsay
Authors: Simoes, P.J.A., Graham, D.R., and Fletcher, L.
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Astronomy and Astrophysics
Publisher:EDP Sciences
ISSN (Online):1432-0746
Copyright Holders:Copyright © 2015 EDP Sciences
First Published:First published in Astronomy and Astrophysics 577:A68
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher.
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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
595181Chromospheric Flares: Observations, Models and Archives (CHROMA)Lyndsay FletcherEuropean Commission (EC)606862P&A - PHYSICS & ASTRONOMY
542081Rolling Programme in Solar and Plasma AstrophysicsLyndsay FletcherScience & Technologies Facilities Council (STFC)ST/I001808/1P&A - PHYSICS & ASTRONOMY
631581Consolidated grant in solar and astrophysical plasmasLyndsay FletcherScience & Technologies Facilities Council (STFC)ST/L000741/1S&E P&A - PHYSICS & ASTRONOMY