Influence of Causally Regulated Ion Outflow on Coupled Magnetosphere-Ionosphere Dynamics

Abstract:

Feedback loops between the magnetosphere and ionosphere cause the coupled system to exhibit complex internal dynamics even under steady external driving conditions. An important feedback pathway is the manner by which magnetospheric energy deposited in the ionosphere is transformed into ion outflows that will affect the future deposition of magnetospheric energy. Using numerical simulations, we demonstrate that the way that ion outflows are regulated by magnetospheric inputs has a profound effect on the emergent behavior of the coupled system. The simulations presented use the multi-fluid Lyon-Fedder-Mobarry (MFLFM) MHD model two-way coupled to the ionosphere/polar wind model (IPWM). IPWM includes the H+ and O+ polar wind as well as a phenomenological treatment of energetic O+ accelerated by wave-particle interactions (WPI). The coupled simulations are highly sensitive to the way that the WPI in IPWM is regulated by inputs from MFLFM. The average hemispheric outflow rate alone is not an adequate predictor of the coupled dynamics that will emerge. Simulations with steady ion outflow tend to settle into a steady magnetospheric convection (SMC) state, whereas simulations with highly impulsive bursts of ion outflow exhibit much more active magnetotail dynamics. Some of the simulations exhibit magnetospheric sawtooth oscillations where quasi-periodic substorms appear in response to the causally driven ion outflow