Bow Shock Position: Observations and Models

Abstract

The set of MAGION-4 and GEOTAIL bow shock crossings, which covers a broad range of latitudes and local times, was completed with solar wind and interplanetary magnetic field observations to determine upstream conditions. The solar wind dynamic pressure varied from 1 to 12 nPa and the Alfvenic Mach number from 4 to 50 and thus these observations provide an excellent opportunity to test empirical models describing the bow shock position as a function of upstream parameters. We have calculated the bow shock positions predicted by various models and determined the distance between observed and predicted locations. We have tested influence of the solar wind and interplanetary magnetic field fluctuations, solar wind aberration, Mach number, and magnetic field strength on the precision of the investigated models. The results show that the uncertainty of the prediction of the bow shock position cannot be explained by errors in the determination of upstream parameters, and that either additional parameters or new interactions should be incorporated into a new model.