Astronomy and Astrophysics – Astrophysics
Scientific paper
Dec 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011agufmsh41a1897g&link_type=abstract
American Geophysical Union, Fall Meeting 2011, abstract #SH41A-1897
Astronomy and Astrophysics
Astrophysics
[7514] Solar Physics, Astrophysics, And Astronomy / Energetic Particles
Scientific paper
A standing "termination" shock in the region near where magnetic reconnection occurs in a solar flare is predicted to result from the interaction of supersonic plasma from the reconnection outflow and the magnetic field in post-flare loops. Here we report a study of the acceleration of electrons in flare termination shocks. We investigate the electron energization process by utilizing a combination of hybrid (kinetic ions and fluid electron) simulations and test particle simulations. The motions of test-particle electrons are integrated numerically in a time-dependent field determined by a two-dimensional hybrid simulation. The shock is driven by injecting plasma towards a rigid wall one end of the simulation box, which generates a fast mode, perpendicular shock with a compression ratio about 2.0 similar to previous MHD simulations of the flaring region and associated termination shock. We also expect the outflow from the reconnection region to be turbulent. We show by including turbulence in our simulations, a thermal population of electrons can be efficiently acceleration by perpendicular shocks up to energies of MeV or more within about 100 ion gyroperiods, for parameters typical of the coronal plasma. The acceleration efficiency is critically dependent on turbulence amplitude and coherence length. For sufficient amplitude of turbulence, the number of energetic electrons (>15keV) can reach more than 10% of total number of electrons in the simulation. This result may help explain hard X-ray sources observed in the region above magnetic loops in solar flares (e.g., Masuda et al. 1995 and Krucker et al. 2010).
Giacalone Joe
Guo Fenzhuo
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