Self-consistent inner magnetosphere simulation driven by a global MHD model

Abstract

We present results from a one-way coupling between the kinetic Ring Current Atmosphere Interactions Model with Self-Consistent B field (RAM-SCB) and the Space Weather Modeling Framework (SWMF). RAM-SCB obtains plasma distribution and magnetic field at model boundaries from the Block Adaptive Tree Solar Wind Roe Upwind Scheme (BATS-R-US) magnetohydrodynamics (MHD) model and convection potentials from the Ridley Ionosphere Model within SWMF. We simulate the large geomagnetic storm of 31 August 2005 (minimum SYM-H of -116 nT). Comparing SWMF output with Los Alamos National Laboratory geostationary satellite data, we find SWMF plasma to be too cold and dense if assumed to consist only of protons; this problem is alleviated if heavier ions are considered. With SWMF inputs, we find that RAM-SCB reproduces well storm time magnetosphere features: ring current morphology, dusk side peak, pitch angle anisotropy, and total energy. The RAM-SCB ring current and Dst are stronger than the SWMF ones and reproduce observations much better. The calculated field-aligned currents (FAC) compare reasonably well with 2 h averaged pictures from Iridium satellite data. As the ring current peak rotates duskward in the storm main phase, the region 2 FACs rotate toward noon, a feature also seen in observations. Finally, the RAM-SCB magnetic field outperforms both the dipole and the BATS-R-US field at Cluster and Polar spacecraft locations. This study shows the importance of a kinetic self-consistent approach and the sensitive dependence of the storm time inner magnetosphere on plasma sheet conditions and the cross polar cap potential. The study showcases the RAM-SCB capability as an inner magnetosphere module coupled with a global MHD model. Copyright 2010 by the American Geophysical Union.