Modulation of galactic cosmic ray particles observed on board the ULYSSES spacecraft

Abstract

The cosmic ray flux observed with the Kiel Electron Telescope on board the ULYSSES spaceprobe varies with solar activity as well as with heliospheric position. Determination of spatial gradients requires a careful analysis of the influences of the current sheet tilt angle, the number of major solar flares, interplanetary shocks and interaction regions evolving in the expanding solar wind. In this paper we concentrate on nuclei with rigidity above 1 GV. We discuss the effects of the variable solar activity in the declining phase of the present solar cycle and the variation with radial distance during the in ecliptic mission period as a basis for separating latitudinal effects. We show that during this phase of the solar cycle modulation of GV nuclei is ordered by temporal evolution, radial distance and small latitudinal effects up to latitudes of 50° South. We discuss the influence on GV nuclei of a disturbance in early 1994 when ULYSSES was beyond 50° South.