Multiple spacecraft observations of interplanetary shocks: Shock-normal oscillations and their effects

Abstract

Observations of interplanetary shocks with multiple spacecraft and multiple instruments has permitted the determination of their average shock normals with unprecedented accuracy. Nevertheless there are still local deviations from the best-fit normal. These deviations in general appear to be less than 5° but on occasion can be of the order of 20° or more. These fluctuating normals and the fluctuating upstream field can cause variations in the downstream field strength even when the upstream field strength is constant. This behavior has important consequences for the appearance of quasi-parallel shocks. Precursor waves which stand on the shock ramp and do not propagate or are not convected across the shock front do not affect the downstream field.