Auroral electron dispersion below inverted‐V energies: Resonant deceleration and acceleration by Alfvén waves

Abstract

Rocket observations of electron time dispersion which occurs at energies below the primary inverted‐V electron precipitation exhibit a variety of characteristics in the dispersion timescale and flux intensity distribution. We present simulation results that illustrate how different dispersion signatures can be produced by resonant acceleration and deceleration of auroral electrons by inertial Alfvén waves. We investigate the individual effects of relevant parameters such as the altitude of the inverted‐V potential, Alfvén wave amplitude, wave velocity, and source electron population. The energies to which Alfvén waves can accelerate electrons are primarily determined by the peak Alfvén speed below the DC potential drop and to a lesser extent by the amplitude of the wave parallel electric field. The observed electron signatures can be used to obtain information about the peak Alfvén speed, the wave parallel electric field, the DC electric field, and plasma environment through which the waves propagate.