Colloquium: Global modeling of transport in the magnetosphere
During geomagnetically active periods ions and electrons are transported from the magnetotail into the ring current in the inner magnetosphere. The transpot of plasma into the ring current occurs at different spatial and temporal scales, from global quasi-steady convection to bursty bulk flows (BBFs), with typical cross-tail extents of 1-3 Earth radii. During its enhancement, the ring current plays a critical role in regulating the coupling between the magnetosphere and ionosphere. Ring current ions build up plasma pressure in the inner magnetosphere and will drive field-aligned currents which must close in the ionosphere, while electrons will lead to diffuse precipitation and enhanced ionospheric conductance which shape the ionospheric path of current closure. The ionospheric current closure will in turn couple to the thermospheric neutral population, via Joule heating, and alter the dynamics of the plasmasphere, via the penetration electric field in the inner magnetosphere.
Understanding the relative role of convection at different spatial scales in both the buildup of the ring current and its broader effects on geospace coupling is an area of active interest and one of the core science questions of the Center for Geospace Storms. In this talk I will describe how addressing this question has informed the development of the Multiscale Atmosphere Geospace Environment (MAGE) model and highlight several recent modeling studies which illustrate the central role of mesoscale processes in magnetospheric transport.