A ULYSSES COSMIC-RAY LATITUDE GRADIENT OBSERVATION AND MODULATION MODELS

The 'EPAC' instrument on Ulysses is sensitive to relativistic cosmic r ays when far from Jupiter and in the absence of energetic solar partic les. Measurement of the latitude gradient of these particles, after co rrection for time variations, has been made for the 1993-1994 south po lar pass. The average magnitude of the gradient is about the same or s maller than predicted by a model which includes full gradient drift. H owever, the latitude dependence of the solar plasma output into interp lanetary space (including fast-stream and magnetic turbulence effects) seems to be important in determining the magnitude of modulation.