Among other things, solar flares are accompanied by the production ofenergetic electrons as seen in the nonthermal radio and X-rayradiation of the Sun. Observations of the RHESSI satellite show that1032-1036 nonthermal electrons are produced per secondduring flares. They are related to an energy flux in the range1018-1022 W. These electrons play an important role, sincethey carry a substantial part of the energy released during a flare.In which way so many electrons are accelerated up to high energiesduring a fraction of a second is still an open question. By means ofradio and hard X-ray data, we investigate under which conditions thisacceleration happens in the corona. The flare is considered in theframework of magnetic reconnection. The conditions in the accelerationregion in the corona are deduced by using the conservation of thetotal electron number and energy. In the inflow region of the magneticreconnection site, there are typical electron number densities ofabout 2.07 x 109 cm-3 and magnetic fields ofabout 46 G.These are regions with high Alfvén speeds of about 2200 km s-1. Then,sufficient energetic electrons (as required by the RHESSIobservations) are only generated if the plasma inflow towards thereconnection site has Alfvén-Mach numbers in the range 0.1-1, whichcan lead to a super-Alfvénic outflow with speeds up to 3100 kms-1.
Authors: G. Mann and A. Warmuth
Publication Status: Published in Astron. and Astrophys.
Last Modified: 2011-03-30 08:57