ON THE FORM OF THE FLOW IN THE MAGNETOSHEATH

The form of the flow field in the subsonic and transsonic magnetosheath has received little attention since the proposal of a depletion layer adjacent to the magnetopause by Zwan and Wolf. Recently, observations of density enhancements just upstream of the magnetopause which have been interpreted as slow mode compressional fronts appear to contradict the earlier suggestions. In this paper we describe the reason for the formation of an upstream compressional front standing near the magnetopause, describe its form and geometry, and explain the likely relationship between the compression region and a depletion layer. The model accounts for the variation of density and magnetic field strength with radial distance from the magnetopause and makes predictions regarding the orientation and geometry of the front.