Influence of cusp O⁺ outflow on magnetotail dynamics in a multifluid MHD model of the magnetosphere

A multifluid version of the Lyon-Fedder-Mobarry global simulation model has been used to investigate the effects of outflowing ionospheric O⁺ on the magnetosphere-ionosphere system. To quantify these effects, we specify the number density, upward parallel velocity, and temperature of the O⁺ outflow in a limited area of the low-altitude simulation boundary representing the projection of cusp, cleft, and low-latitude boundary layer. A baseline simulation without O⁺ outflow is compared with simulations with a range of fluxes and initial velocities. In the cases with high fluxes, it is shown that the configuration of the magnetosphere is dramatically changed. In particular, the cross-polar cap potential is reduced, the polar cap area is increased, and the nightside reconnection line is moved earthward. Furthermore, in one case, the O⁺ outflow leads to the onset of a second substorm not seen in the other simulation runs.