The Fate of Plasmasphere Material: Is Recirculated Material a Significant Contributor to the Ring Current?

Abstract:

The fate of Plasmasphere material once it is drained out of the plasmasphere through a plume is unknown. The material can either be swept away with the solar wind, lost to the earth system, or it may be recirculated into the magnetosphere system. Recirculating plasmasphere material could plausibly enter the central plasma sheet and contribute to the ring current. Using observations to study the fate of the plasmasphere material is difficult as it is mostly hydrogen and becomes homogenized with solar wind hydrogen once it passes through the day side magnetopause. Numerical models, however, can keep the material distinct, opening the possibility of resolving the question using simulations.

This work uses numerical models to answer two questions. Does any plasmasphere material recirculate back into the magnetosphere? What effect, if any, does recirculated material have on the formation of the ring current? This is done by studying simulations produced by the Space Weather Modeling Framework (SWMF) configured to couple three models: the Block Adaptive Tree Solar Roe Up Wind Scheme (BATS-R-US) model, the Dynamic Global Core Plasma Model (DGCPM) plasmasphere model, and the Ridley Ionosphere Model (RIM). For these simulations BATS-R-US is configured to use two fluids. The first fluid represents currently accepted sources of ring current material, namely the solar wind and high latitude ionospheric outflow. The second fluid represents the plasmasphere. Within 10 Earth Radii (RE) the dynamics in BATS-R-US on closed field lines are dictated by coupling with the DGCPM. DGCPM passes the density of material in the plasmasphere to BATS-R-US. RIM passes electric field information to both BATS-R-US and DGPCM while receiving current density form BATS-R-US. The outputs of the simulation are examined to evaluate plume recirculation. Also, the outputs are used as inputs for the Ring current Atmosphere interaction Model with Self Consistent (B)Magnetic Field (RAM-SCB) model of the ring current in a one-way coupling. The purpose of the one way coupling to RAM-SCB is to see if the recirculated plasma is important in the evolution of the ring current during the storm. The fate of the plasmasphere material and any possible effect on the ring current is then studied in an idealized storm and a Co-rotating Interaction Region (CIR) event.