Multiple spacecraft observations of interplanetary shocks: Four spacecraft determination of shock normals

Abstract

ISEE 1, 2, 3, IMP 8, and Prognoz 7 observations of interplanetary shocks in 1978 and 1979 provide five instances where a single shock is observed by four spacecraft. These observations are used to determine best‐fit normals for these five shocks. In addition to providing well‐documented shocks for future investigations these data allow us to evaluate the accuracy of several shock normal determination techniques. When the angle between upstream and downstream magnetic field is greater than 20°, magnetic coplanarity can be an accurate single spacecraft method. However, no technique based solely on the magnetic measurements at one or multiple sites was universally accurate. Thus, we recommend using overdetermined shock normal solutions whenever possible, utilizing plasma measurements, separation vectors, and time delays together with magnetic constraints.