Stochastic Acceleration of Low‐Energy Electrons in Plasmas with Finite Temperature

This paper extends our earlier work on the acceleration of low-energyelectrons by plasma turbulence to include the effects of finite temperature ofthe plasma. We consider the resonant interaction of thermal electrons with thewhole transverse branch of plasma waves propagating along the magnetic field.We show that our earlier published results for acceleration of low-energyelectrons can be applied to the case of finite temperature if a sufficientlevel of turbulence is present. From comparison of the acceleration rate of thethermal particles with the decay rate of the waves with which they interact, wedetermine the required energy density of the waves as a fraction of themagnetic energy density, so that a substantial fraction of the backgroundplasma electrons can be accelerated. The dependence of this value on the plasmaparameter alpha = omega_pe / Omega_e (the ratio of electron plasma frequency toelectron gyrofrequency), plasma temperature, and turbulence spectral parametersis quantified. We show that the result is most sensitive to the plasmaparameter alpha. We estimate the required level of total turbulence bycalculating the level of turbulence required for the initial acceleration ofthermal electrons and that required for further acceleration to higherenergies