Magnetosphere-Ionosphere-Thermosphere Coupling in Geospace Dynamics

Magnetosphere-Ionosphere-Thermosphere (M-I-T) coupling entails three primary agents of change: electromagnetic power flows, charged-particle precipitation and ionospheric ion outflows. The dynamics of all three are intertwined. For example, electromagnetic energy deposition in the I-T region is structured by the electrical conductivity distribution and its gradients, which is regulated by precipitation. Ionospheric outflows are energized by EM power flows into the topside ionosphere and low-altitude magnetosphere, with the source and flux of the outflowing ions regulated to a large extent by Joule heating, soft precipitation, and the thermospheric scale height. Global simulations show that magnetospheric structure and dynamics are also controlled by the distribution of ionospheric conductivity and by mass loading from ionospheric outflows. Understanding and predicting the state of the coupled geospace system therefore requires accurate knowledge of the processes that control these agents and their interactions. In this presentation, I will use results from global simulations (themselves a work in progress) to illustrate some of the important scale interactions between EM power flows, charged-particle precipitation and ionospheric ion outflows and their consequences on geospace dynamics. Key deficiencies in empirical and theoretical understanding of the change agents of M-I-T coupling will be highlighted together with recent progress in modeling them.