Parallel Electric Field and Electron Acceleration: an Advanced Model

Abstract

A kinetic theory is necessary to explain the electron flows forming strong field-aligned currents in the auroral region. Its construction in this paper is based on the following propositions. (a) In the equatorial region, the arrival of electrons through the lateral surface of the magnetic flux tube is compensated for by their escape along the magnetic field. This is provided by action of the pitch-angle diffusion mechanism in the presence of plasma turbulence concentrated in this region. (b) Outside the equatorial region, the distribution functions of trapped and precipitating particles become “frozen.” The distributions and particle concentrations are calculated there in a model with conservation of the total energy and the magnetic moment. (c) The quasi-neutrality condition yields a large-scale parallel electric field, which contributes to the conserved total energy. In this field, the electron acceleration occurs, causing strong field-aligned currents directed upward from the ionosphere.