WHISTLER-MODE WAVE GENERATION AROUND INTERPLANETARY SHOCKS IN AND OUTOF THE ECLIPTIC-PLANE

We present a study of whistler-mode wave generation and wave particle interaction in the vicinity of interplanetary shocks in and out of the ecliptic plane, as observed by the Ulysses spacecraft. We focus here on one shock in the ecliptic plane as a reference and three shocks obt ained at -30, -54 and -55.4 degrees of heliographic latitude respectiv ely. Generally the whistler-mode waves (measured in the frequency rang e 0.22-448 Hz) are observed downstream of the shocks where they persis t for some hours. From the electron distribution functions in the ener gy range 1.6 to 862 eV, we compute the temperature anisotropy and the wave growth rate of the electromagnetic electron cyclotron instability for the case of parallel propagation of the waves with respect to the interplanetary magnetic field (IMF) B. In general, in agreement with the wave measurements, the instability grows only downstream of the sh ock fronts. Following the wave activity, velocity space diffusion of t he electrons results in a marginally stable state with some sporadic f luctuations. Broadening of the wave reduced frequency range of the ins tability and an increase of the temperature anisotropy with latitude a re observed.