Magnetospheric and Atmospheric Controls of Giant Planet Auroral Currents

Ray, Licia C (2018) Magnetospheric and Atmospheric Controls of Giant Planet Auroral Currents. In: Electric Currents in Geospace and Beyond. Geophysical Monograph Series . American Geophysical Union. ISBN 9781119324492

Abstract

Planetary atmospheres and their surrounding plasma environments exchange energy and momentum through magnetosphere‐ionosphere‐thermosphere (MIT) coupling. This fundamental process is mediated by the planetary magnetic field, which connects the ionosphere, the ionized part of the atmosphere, to the magnetospheric plasma. The ionosphere, in turn, is collisionally coupled to the thermosphere, the upper portion of the neutral atmosphere. Momentum and energy are communicated through magnetic fields and electric fields generated by plasma flows, wave‐particle interactions, varying gradients in the magnetic field. Associated currents are generated that flow along the magnetic field, diverging perpendicularly to the magnetic field in the magnetospheric equator and ionosphere to convey J × B forces in the local plasma populations. An observable consequence of MIT coupling is the aurora, which has been observed at every magnetized planet with an atmosphere. While the presence of aurora is ubiquitous, the phenomenology of the emissions is system dependent, detailing differences in the currents at work. We discuss auroral currents at the giant planets and how the planetary magnetospheres and atmospheres contribute to and control the current systems.