Generation of short‐burst radiation through Alfvénic acceleration of auroral electrons

Abstract

A comparison of modeled simulation results with in situ observations is presented in an effort to better understand the generation mechanism of short‐burst radiation (AKR) observed in the Alfvénic acceleration region. The simulation is performed using a linear gyrofluid Alfvén model to generate propagating inertial Alfvén waves with a test particle scheme to study the behavior of electrons under the influence of waves. The observations are taken from the wave and plasma instruments on board the Fast Auroral Snapshot (FAST) satellite. We find that single‐ and multiple‐electron shell distributions are produced as a result of parallel electric fields generated from inertial Alfvén waves. Electrons outside the loss cone are reflected back up the flux tube because of the mirror force forming electron conics. Distributions obtained from this simulation resemble the observed electron distributions in the Alfvénic auroral acceleration region where short‐burst radiations were present. Multiple‐shell distributions as well as electron conics are unstable, making them candidates for triggering the electron‐cyclotron maser instability. Hence we suggest that these unstable distributions, resulting from the effects of inertial Alfvén wave, could be the source of the observed short‐burst radiation in the terrestrial auroral zone magnetosphere‐ionosphere coupling region. We also briefly discuss the application of this general mechanism to explain the Io‐associated S‐bursts observed emanating from the Jovian magnetosphere.