Assessment of possible mechanisms responsible for dawn-dusk asymmetry of the magnetopause

Abstract:

The dawn and dusk magnetopause may behave differently.
First, the vxB electric field, with v the magnetosheath flow and B the geomagnetic field, points outward at dawn and inward at dusk. Since the ions and electrons, with their different gyroradii, respond differently to a change of sign of this electric field, the structure of the magnetopause will be different.
Second, there may be systematic differences in the dawn and dusk conditions in the magnetosheath and/or in the magnetosphere, which can also lead to a dawn-dusk asymmetry of the magnetopause structure. Such differences include: a dawnward offset of the magnetosheath flow stagnation point, differences in magnetic field draping due to the Parker spiral orientation, the possible presence of cold plasmaspheric plume material predominantly in the post-noon sector, dawn-dusk differences in the low-latitude boundary layer, etc.
We compute the internal structure of the magnetopause using a kinetic model for various configurations to illustrate the expected degree of asymmetry.