Model of Bow Shock and Magnetopause Surfaces

The present models describing location and shape of the magnetopause and the bow shock are based on a statistical evaluation of magnetopause and bow shock crossings. The crossings have been usually identified by time consuming visual inspections of plots or by automated methods which are less reliable. In this paper, we present a new automatic method that can be used for identification of both boundaries if several criteria are fulfilled: 1) available magnetic field and plasma data from a solar wind monitor, and 2) measurements of the magnetic field and plasma density from a sounding spacecraft. We used one-minute medians of continuous measurements of these parameters by a particular spacecraft and distinguished three regions - the solar wind, the magnetosheath, and the inner magnetosphere - according to the magnetic field and plasma density ratios. We explain the method, apply its results to Themis observations, and verify them using our set of magnetopause and bow shock crossings observed by the Themis spacecraft.