Multi-Spacecraft Observations of Interplanetary Shocks in the Solar Wind and Magnetosheath

Dr. Adam Szabo
NASA Goddard Space Flight Center

The ISTP spacecraft provided a wealth of observations of interplanetary (IP) shocks of various kinds both in the ambient solar wind and in the Earth's magnetosheath. The most comprehensive shock fitting techniques reveal that a number of IP shocks significantly deviate from a simple planar geometry on the scale-length of the magnetosphere. This complicates the determination of the precise arrival time and location of the shocks at the magnetopause surface. It will be shown that the local geometry of the shock fronts is also dependent on the shock driver. Specifically, large magnetic clouds tend to drive more planar IP shocks. Once the IP shock crosses the Earth's bow shock into the subsonic regions of the magnetosheath, they travel as fast mode pressure pulses. Unlike tangential and rotational discontinuities, the pressure pulses of IP shocks maintain their original geometry within the accuracy allowed by current observations providing some hope that upstream solar wind monitors can be used to predict to some degree (+/- 5-10 minutes) the arrival times of geoeffective shock fronts.