Generation of highly energetic electrons at reconnection outflow shocks during solar flares
Abstract
Context: During solar flares a large amount of energy is suddenly released and partly transferred into energetic electrons. They are of special interest since a substantial part of the energy released during a flare is deposited into the energetic electrons. RHESSI observations, e.g. of the 2003 October 28 solar event, show that 1036 electrons with energies >20 keV are typically produced per second during large flares. They are related to a power of about 1022 W. It is still an open question in which way so many electrons are accelerated up to high energies during a fraction of a second.
Aims: Within the framework of the magnetic reconnection scenario, jets appear in the outflow region and can establish standing fast-mode shocks if they penetrate the surrounding plasma with super-Alfvénic speed. It is our aim to show that this shock can be the source of the energetic electrons produced during flares.
Methods: The electrons are regarded as energized by shock drift acceleration. The process is necessarily treated in a fully relativistic manner. The resulting distribution function of accelerated electrons is a loss-cone one and it allows to calculate the differential electron flux, which can be compared with RHESSI.
Results: The theoretically obtained fluxes of energetic electrons agree with the observed ones as demonstrated for the 2003 October 28 solar event.
- Publication:
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Astronomy and Astrophysics
- Pub Date:
- February 2009
- DOI:
- 10.1051/0004-6361:200810099
- Bibcode:
- 2009A&A...494..669M
- Keywords:
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- acceleration of particles;
- shock waves;
- Sun: flares;
- Sun: X-rays;
- gamma rays;
- Sun: radio radiation