Low frequency plasma turbulence and high energy particles at CIR-related shock waves

We present initial results from a survey of the low frequency magnetic fiel d turbulence measured at the forward/reverse shock pairs associated with th e interaction regions of high and low speed solar wind streams (CIRs). The magnetic field data are taken from vector helium and fluxgate magnetometer observations (VHM/FGM) aboard the Ulysses spacecraft between July 1992 and December 1993. A turbulence measure is defined as total wave power in the f requency range available from the raw data. This quantity is computed for t he up- and downstream regions of the CIR-shocks and compared with the fluxe s of 1 MeV protons and roughly 1 MeV/nucl. helium (Ulysses-EPAC measurement s) at the time of shock crossing. We find a poor correlation between the up stream magnetic field turbulence and the high energy particle fluxes, and a high correlation between these quantities in the downstream region. The co rrelation between particle flux and field turbulence is best for the region roughly one gyroradius (of the high energy particles) downstream of the sh ock. Thus we conclude that wave-particle interactions in the downstream reg ion, especially in the direct vicinity of the shock transition play an esse ntial role for the acceleration of particles at CIR-related shock waves.