A Statistical Analysis of the Fluctuations in the Upstream and Downstream Plasmas of 109 Strong-Compression Interplanetary Shocks at 1 AU

The upstream and downstream plasmas of 109 strong-compression forward interplanetary shocks are statistically analyzed using 3-s measurements from the WIND spacecraft. The goal is a comparison of the fluctuation properties of downstream plasmas in comparison with the fluctuation properties of upstream plasmas in the inertial range of frequencies and the magnetic-structure range of spatial scales. The shocks all have density compression rations of similar to 2 or more. When possible, each shock is categorized according to the type of solar wind plasma it propagates through: 15 shocks are in coronal-hole-origin plasma, 42 shocks are in streamer-belt-origin plasma, 36 shocks are in sector-reversal-region plasmas, and 11 shocks are in ejecta plasma. The statistical study examines magnetic field and velocity spectral indices, the Alfvenicity, the fluctuation amplitudes, Alfven ratios, the degree of plasma inhomogeneity, and Taylor microscales, looking in particular at (1) fluctuation values downstream that are related to fluctuation values upstream and (2) systematic differences in fluctuation values associated with the type of plasma. It is argued that inhomogeneity of the downstream plasma can be caused by spatial variations in the shock normal angle theta(Bn) caused by field direction variations in the upstream magnetic structure. The importance of determining the type of plasma that the shock propagates through is established.