Remote sensing of two-dimensional magnetopause structures

Abstract

The study presents a technique for analyzing remote measurements made by a single spacecraft of 2D disturbances in the ambient magnetosheath or magnetospheric magnetic field caused, for example, by flux transfer events or pressure pulses. The methodology is based on a recent linear theory for isentropic field-aligned MHD flow over gently sloping 2D obstacles. The technique uses only magnetic field measurements and can provide information about the orientation and actual cross-sectional shape of the event, as well as information about the spacecraft trajectory relative to the bulge. Analysis of two sample events, one recorded by the AMPTE/IRM spacecraft in the magnetosheath and the other by AMPTE/CCE in the magnetosphere, indicates that the bulges on the magnetopause surface causing the magnetic field and flow perturbations for these events did not have the semicircular cross section suggested in previous work; instead they had a more elongated shape, the dimension tangential to the magnetopause being substantially larger than that normal to it.