LATITUDE VARIATIONS OF SIMILAR-TO-7 MEV AND GREATER-THAN-300 MEV COSMIC-RAY ELECTRON-FLUXES IN THE HELIOSPHERE - ULYSSES COSPIN KET RESULTSAND IMPLICATIONS/

The 160 degrees latitude scan performed in less than one year between summer 1994 and summer 1995 by Ulysses allowed us to obtain unique dat a about the latitudinal dependence of the cosmic ray fluxes. We presen t in this paper results on the electron component derived from the COS PIN/KET instrument onboard Ulysses, both at MeV and GeV energies. The variations of the 1 to 7 GV electron fluxes do not show any feature wh ich could be attributed to a latitude dependence. This observation dev iates from the variations of the proton fluxes of similar rigidities. The electron/proton ratio is shown to depend unambiguously on latitude during the fast latitude scan of Ulysses. This latitudinal dependence can in fact be traced back in our data to at least mid 1993 when Ulys ses left the streamer belt region. The time profiles of high energy el ectrons and protons are also compared with the predictions of a time d ependent modulation model. It is found that our data can be reasonably well accounted for by assuming time-dependent increasing drift effect s. asymmetric perpendicular diffusion and a rigidity (P) dependence fo r the parallel mean free path derived by Bieber et al. (1991), i.e. pr oportional to p(0.3) between 0.9 and 2.5 GV. Regarding the similar to 7 MeV electrons, we do not see any flux excess at the poles. This is i n contradiction with the claim made by Simnett et al. (1995) of an ent ry of MeV galactic electrons over the poles. The flux excess they clai m to have detected is inconsistent with our electron data by 30 to 60 standard deviations, depending on the spectral shape. We argue that th is inconsistency may be attributed to a proton induced background in t he Simnett et al. data. The KET data imply a conservative upper limit of 3.2 elec/m(2).s.sr.MeV for the galactic electron Bur at this energy .