ENTRY OF GALACTIC ELECTRONS INTO THE HIGH-LATITUDE HELIOSPHERE

Evidence is presented for the first detection of galactic cosmic ray e lectrons in the general energy range 1 to 20 MeV by the HI-SCALE instr ument on Ulysses as it passed over the solar poles. The electrons mani fest themselves by a strong latitude dependence of the background coun ting rates in the HI-SCALE detectors, in excess of that predicted from the COSPIN measurements. The majority of the detected electrons have penetrated the housing around the detectors; the apparent spectrum of this excess is completely inconsistent with penetrating ions, whatever their spectrum. We have compared the inferred electron flux with an e xtrapolation of the cosmic ray electron spectrum measured in the eclip tic plane and inferred from radio astronomy at greater than or similar to 1 GeV and conclude that the galactic spectrum does not continue as a power law down to a few MeV.