STOCHASTIC ACCELERATION OF LOW-ENERGY ELECTRONS IN PLASMAS WITH FINITE-TEMPERATURE

This paper extends our earlier work on the acceleration of low-energy electrons by plasma turbulence to include the effects of finite temper ature of the plasma. We consider the resonant interaction of thermal e lectrons with the whole transverse branch of plasma waves propagating along the magnetic held. We show that our earlier published results fo r acceleration of low-energy electrons can be applied to the case of f inite temperature if a sufficient level of turbulence is present. From comparison of the acceleration rate of the thermal particles to the d ecay rate of the waves with which they interact, we determine the requ ired energy density of the waves as a fraction of the magnetic energy density, so that a substantial fraction of the background plasma elect rons can be accelerated. The dependence of this value on the plasma pa rameter alpha = omega(pe)/Omega(e) (the ratio of electron plasma frequ ency to electron gyrofrequency), plasma temperature, and turbulence sp ectral parameters is quantified. We show that the result is most sensi tive to the plasma parameter alpha. We estimate the required level of total turbulence by calculating the level of turbulence required for t he initial acceleration of thermal electrons and that required for fur ther acceleration to higher energies.