E. P. Kontar, H. Ratcliffe, N. H. Bian
Context. High energy electrons accelerated during solar flare are abundant in
the solar corona and in the interplanetary space. Commonly, the number and the
energy of non-thermal electrons at the Sun is estimated using hard X-ray (HXR)
spectral observations (e.g. RHESSI) and a single-particle collisional
approximation. Aims. To investigate the role of the spectrally evolving
Langmuir turbulence on the population of energetic electrons in the solar
corona. Methods. We numerically simulate the relaxation of a power-law
non-thermal electron population in a collisional inhomogeneous plasma including
wave-particle, and wave-wave interactions. Results. The numerical simulations
show that the long-time evolution of electron population above 20 keV deviates
substantially from the collisional approximation when wave-particle
interactions in non-uniform plasma are taken into account. The evolution of
Langmuir wave spectrum towards smaller wavenumbers, due to large-scale density
fluctuations and wave-wave interactions, leads to an effective acceleration of
electrons. Furthermore, the time-integrated spectrum of non-thermal electrons,
which is normally observed with HXR above 20 keV, is noticeably increased due
to acceleration of non-thermal electrons by Langmuir waves. Conclusions. The
results show that the observed HXR spectrum, when interpreted in terms of
collisional relaxation, can lead to an overestimated number and energy of
energetic electrons accelerated in the corona.
View original:
http://arxiv.org/abs/1112.4448
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