Signatures of shock drivers in the solar wind and their dependence on the solar source location

Abstract

Solar wind and energetic ion observations following 40 interplanetary shocks with well‐established solar source locations have been examined in order to determine whether signatures characteristic of the coronal material forming the shock driver are present. The signatures considered include magnetic‐field‐aligned bidirectional ion flows observed by the ISEE 3 and IMP 8 spacecraft; bidirectional solar wind electron heat fluxes; solar wind plasma proton and electron temperature depressions; low‐β plasma; enhanced, low‐variance magnetic fields; and energetic ion depressions. Several shock driver signatures are commonly observed following shocks originating from within ∼50° of central meridian and are generally absent for other events. We conclude that shock drivers generally extend up to ∼100° in longitude, centered on the solar source longitude. A particular shock driver signature is typically found following ∼80% of shocks from near‐central meridian events. However, only ∼20% of shocks from near‐central meridian events are associated with the bidirectional 35‐1000 keV ion events discussed by Marsden et al. (1987). Since shocks from central meridian events are not usually associated with all the shock driver signatures examined, the absence of a driver cannot be confirmed from consideration of one of these signatures alone. We also find evidence that a few bidirectional energetic ion and solar wind electron heat flux events following shocks (in particular from far eastern sources) may occur on open field lines outside of shock drivers.