Interplanetary shocks observed by ULYSSES in the ecliptic plane as a function of the heliocentric distance

Abstract

During its mission in the ecliptic plane, the Ulysses spacecraft crossed many heliospheric large-scale structures. Several interplanetary (IP) shocks were identified and characterized using the radio receiver, magnetometer and proton analyser aboard. The spectroscopy of the thermal noise measured by the radio receiver gives the plasma electron density and temperature. We present a list of IP shocks detected between 1 and 5 AU. The upstream beta factor beta_u is estimated using the electron, proton and magnetic field data. The angle theta_BN between the upstream magnetic field and the shock normal, and the Alfvén Mach number M_A are deduced from the Rankine-Hugoniot relations using beta_u, the electron density N_ed and N_eu, and the magnetic field B_d andB_u . We investigate the correlation of the shock strengthN_ed /N_eu with the heliocentric distance. Within 5 AU, the shock strength is found to increase with increasing distance to the Sun for shocks associated with corotating interaction regions, while it presents no significant dependence in distance for coronal mass ejection shocks.