Magnetospheric Convection

Abstract

Ideally, in the convection problem we should start at the bow shock and solve self-consistently for energy, momentum and plasma transfer in the complete downstream system. The state of the art is to study individual regions (magnetosheath, tail lobes, high-beta plasma sheet, and Bipolar region) and make assumptions about the boundary conditions connecting them to neighbouring regions. Plasma sheath convection can be approximated by the model of a blunt body immersed in a supersonic or super-Alfvénic flow with some degree of success. Improvements need to include the effects of the dayside-merging and the nightside expansion fan sections of the magnetopause on flow in the plasma sheath. Convection in the Bipolar region is fairly well understood in terms of the calculation scheme proposed by VASYLIUNAS (1972), but a self-consistent determination of the latitude of the high-latitude boundary is needed as well as a better understanding of boundary conditions. Understanding of convection in the high-beta plasma sheet and lobe is still very poor. The energy source is electromagnetic and can be represented as Poynting vector flow from the highlatitude magnetopause. We are still very uncertain as to the energy sink and the plasma sources and sinks in the plasma sheet. In the tail lobes, selfconsistency is needed between the field-line topology (including twists and open-closed configuration) and the location of and merging rate at X lines. Non-MHD processes are important at the boundaries between all the above regions.