Ionospheric Outflow at Jupiter and Saturn

Abstract:

Ionospheric outflow is triggered by the loss of equilibrium along a magnetic field line, generating a flow of plasma from the high latitude regions of a planetary atmosphere into the magnetosphere, and beyond. At Earth, this loss of equilibrium is driven by the Dungey cycle. However, at the gas giants a multitude of processes, related to the rapid planetary rotation rates and plasma sources embedded within the magnetosphere, can perturb a flux tube away from equilibrium. We discuss the implications of different drivers for ionospheric outflow at Jupiter and Saturn. Alongside this, we present the results of our recent study, in which a 1D, hydrodynamic model of the transport equations is used to investigate the effects of field-aligned-currents and centrifugal forces on the rate of outflow. We find that the number flux of ionospheric outflow is on average an order of magnitude higher than expected without the additional effects of centrifugal force and field‐aligned currents. The implications of this additional flux will substantially affect the composition and dynamics of the planet's magnetosphere, and therefore should be included in future assessments of these systems.