Plasma plume circulation and impact in an MHD substorm

We investigate the fate of a plasmaspheric plume generated by a discrete period of southward interplanetary magnetic field (IMF) to assess its contribution to plasma sheet and ring current pressure and compare with that for other sources. We use test particle motions in Lyon-Fedder-Mobarry (LFM) global circulation model fields. The inner magnetosphere is simulated with the Comprehensive Ring Current Model (CRCM) model of Fok and Wolf, driven by the transpolar potential developed by the LFM magnetosphere. A variant of the Ober plasmasphere model is embedded within the models and driven by them. Global circulation is stimulated by a period of southward IMF embedded within a long interval of northward IMF. This leads to the production of a well-defined plasmaspheric plume, enhancing the plasma density sunward of the plasmasphere. Test particles are launched with the properties of plasmaspheric ions on the L = 6.6 R-E shell and weighted with densities as specified by the Ober model, as it responds to convection imposed by CRCM. Particles are tracked until they are lost from the system downstream or into the atmosphere, using the Delcourt full equations of motion, implemented for finite element fields. Results are compared with earlier computations of polar and auroral wind outflows. The plume produces an enhanced flow of plasma similar to 10 times the normal polar wind global fluence. However, we find that most of the plasmaspheric wind'' is lost from the magnetosphere such that its contribution to the ring current energy density is comparable to that of the normal polar wind for this type of event.