The effect of ionospheric outflow and magnetospheric composition on the development of a magnetic storm

Simulations using the Space Weather Modeling Framework (SWMF) together with composition measurements from TWINS are used to investigate the global dynamics and energization of ions throughout the magnetosphere during storm time. We address the effect of ionospheric outflow and inner magnetospheric ion composition on the physical processes that control the development of August 5, 2011 magnetic storm. For this purpose we include simulations involving both multi fluid and single fluid MHD for the global magnetosphere. The density at the inner boundary is either set to a constant value or calculated in a self-consistent manner by a multi fluid multi field line polar wind model capable of simulating the ionospheric outflow. We find that multi fluid MHD simulations that include polar outflow produce the best results when modeling a storm, in that the modeled Dst shows the highest correlation with the homologous observed quantity. Changing the composition in the inner magnetosphere in a dynamic way alters the total energy density of the magnetosphere, leading to changes in the magnetic field as well as particle trajectories throughout the simulated domain. Oxygen observations from the TWINS spacecraft show intensifications of the ENA emission during the main phase of the storm, well correlated with substorm injection during that time. Synthetic mass separated ENA images reveal similar features, in direct agreement with the observations.