Generation of electron suprathermal tails in the upper solar atmosphere: Implications for coronal heating

We present a mechanism for the generation of non-Maxwellian electron distri bution function in the upper regions of the solar atmosphere in the presenc e of collisional damping. It is suggested that finite-amplitude, low-freque ncy, obliquely propagating electromagnetic waves can carry a substantial el ectric held component parallel to the mean magnetic field that can be signi ficantly larger than the Dreicer electric held. This long-wavelength electr ic fluctuation is capable of generating high-frequency electron plasma osci llations and low-frequency ion acoustic-like waves. The analysis has been p erformed using 1-1/2D Vlasov and PIC numerical simulations in which both el ectrons and ions are treated kinetically and self consistently. The simulat ion results indicate that high-frequency electron plasma oscillations and l ow-frequency ion acoustic-like waves are generated. The high-frequency elec tron plasma oscillation drives electron plasma turbulence, which subsequent ly is damped out by the background electrons. The turbulence damping result s in electron acceleration and the generation of non-Maxwellian supratherma l tails on timescales short compared to collisional damping. Bulk heating a lso occurs if the fluctuating parallel electric field is strong enough. Thi s study suggests that finite-amplitude, low-frequency, obliquely propagatin g electromagnetic waves can play a significant role in the acceleration and heating of the solar corona electrons and in the coupling of medium and sm all-scale phenomena.