Bow shock's geometry at the magnetospheric flanks

Abstract

The database of IMP 8 bow shock crossings was used to investigate properties of the bow shock's cross section between 10 and 15 RE tailward of Earth in response to selected upstream and magnetospheric parameters. Best-fitted ellipses were derived for each parameter subset and analyzed. We have found that for average solar wind conditions, the shock's cross section moves in the north-south directions by 3.8 RE when the dipole tilt changes from sunward to antisunward orientations. Comparisons with results provided by global three-dimensional MHD simulations of the magnetosphere have shown that the tilt angle effect is likely to be also important for the estimation of the dayside shock wave's position. We have found the orientation of the IMF with respect to the solar wind flow, expressed by the angle θBv, to influence the size and stability of the shock shape/position. The observed Mach number dependence agreed with previous studies and no other significant IMF-induced asymmetries were found. Copyright 2004 by the American Geophysical Union.