Modulation of Jovian and galactic electrons in the heliosphere 1. Latitudinal transport of a few MeV electrons

The heliospheric modulation of galactic and Jovian electrons is studied usi ng a fully three-dimensional, steady state model based on Parker's transpor t equation including the Jovian source. The modulation of low-energy electr ons is a handy tool to establish and to construct a suitable diffusion tens or to assure compatibility between model computations and observations from the Ulysses spacecraft. This is because electron modulation responds direc tly to the energy dependence of the diffusion coefficients below similar to 500 MeV in contrast to protons which experience large adiabatic energy los ses below this energy. The model is used to study the latitudinal transport of both Jovian and 4-20 MeV galactic electrons by illustrating how the ele ctron intensities are affected at different latitudes when enhancing perpen dicular diffusion in the polar direction. In particular, the electron inten sity-time profile along the Ulysses trajectory is calculated for various as sumptions for perpendicular diffusion in the polar direction and compared t o the 3-10 MeV electron flux observed by Ulysses from launch up to the end of the first out of the ecliptic orbit. Comparison of the model computation s and the observations give an indication as to the magnitude of this diffu sion coefficient. The relative contributions of the Jovian and galactic ele ctrons to the total electron intensity is shown along the Ulysses trajector y.