The effect of changing solar wind conditions on the innermagnetosphere and ring current: Amodel data comparison

摘要

We investigate the rate at which the open drift paths in the near-Earth magnetosphere convert to closed paths during events with a sudden northward turning of the interplanetary magnetic field (IMF B_z) after the peak of a geomagnetic storm. The geomagnetic storm on 17 August 2001 with an abrupt turning of the IMF B_z after the peak in SYM-H index is chosen in this study. The Block-Adaptive-Tree Solar-Wind Roe-Type Upwind Scheme model along with the Fok Ring Current (FRC) model available at Community Coordinated Modeling Center is used to model this event. The unique movie maps of the worldwide magnetometer stations are used to compare with the numerical results. The results indicate that ground magnetic disturbance remains asymmetric for some time after the start of the recovery phase even for a storm with abrupt northward turning of the IMF B_z. FRC simulation results suggest that the flow-out losses decrease under weakened magnetospheric convection but at a rate slower than the change in IMF B_z. These results indicate that the flow-out losses rapidly become smaller as the IMF B_z turns northward during the early recovery phase of a storm and the contribution of the tail current to the SYM-H index is important.