Interaction of Fast Steady Flow with Slow Transient Flow: A New Cause of Interplanetary Bz Events
STANFORD UNIV CA CENTER FOR SPACE SCIENCE AND ASTROPHYSICS
Pagination or Media Count:
The occurrence of the nonspiral magnetic field, high helium density, Cold Magnetic Enhancement and counterstreaming suprathermal electron flux in the slow flow around the forward shock indicates that the slow flow is a CME in interplanetary space ICME. The characteristics of the field and plasma in the fast flow around the reverse shock is typical for a high speed stream. Thus the shock pair here appears to be caused by the interaction of a high speed stream with a slow ICME. The fact that a -Bz event occurred in such a shock pair suggests that the slow ICME is disconnected from the Sun. It is shown that compression alone appears to be adequate to explain the large southward IMF component within the shocked plasma because of the large southward field component present in the ICME ahead of the forward shock. In addition, a new method to infer the shock angle and Mach number from the observed upstream plasma Beta and the jump ratios of proton density and total magnetic flux density across a shock is described.