Plasma depletion layer: Event studies with a global model

Abstract

The plasma depletion layer (PDL) is a layer on the sunward side of the magnetopause with lower plasma density and higher magnetic field compared to the corresponding upstream magnetosheath values. In this study we use global simulations of the solar wind-magnetosphere-ionosphere system to compare with Wind PDL observations on the flanks of the magnetopause on 12 January 1996 and 1 January 1999. The consistency between model results and observations shows that the magnetohydrodynamic (MHD) description of the plasma is sufficient to describe the PDL process observed in this region. The simulation also shows that the PDL is stable as long as the interplanetary magnetic field (IMF) has no major variations. Temporal-spatial ambiguities are analyzed for the 1996 event, and a significant difference between the time series and the instantaneous PDL spatial structure is found. A much smoother instantaneous PDL spatial structure is found than observed in the simulated spacecraft time series, which is highly modulated by solar wind and IMF variations. The local, time and latitude dependence of the PDL for the 1996 evento are also obtained from the model that predicts that a thinner PDL occurs near the subsolar point and a thicker PDL exists farther away from that point. Copyright 2003 by the American Geophysical Union.