What causes the variations of the peak intensity of CIR accelerated energetic ion fluxes?

Abstract. The variation of the peak intensity of energetic ions accelerated at CIR related shocks in the interplanetary medium as observed by instruments on board of ULYSSES during its pass towards the south polar region and from the north polar region back to its aphelium is discussed. From ULYSSES measurements alone it cannot be decided whether the observed variation is a function of latitude or of radial distance, as its orbit changes distance and latitude at the same time. Therefore ULYSSES data is compared with earlier observations by the PIONEER and VOYAGER spacecraft and concluded that the major part of the observed variation of the peak intensity seems to be due to a radial distance change, on to which, however, at higher latitudes a latitude dependent feature is superimposed.

Key words. Interplanetary physics (Energetic particles; interplanetary shocks; general)