Effects of anisotropic perpendicular diffusion on the energy and spatial dependence of galactic electron modulation in the heliosphere

Abstract

Perpendicular diffusion enhanced in the polar directions of the heliosphere seems required in numerical models based on Parker's transport equation for cosmic rays, especially in explaining the small latitudinal gradients observed for protons by the Ulysses spacecraft during its fast latitude scan. This modulation topic is further studied using electron modulation. The enhancement generally produced an increase in modulation for both the A > 0 (e.g. ∼1990 to ∼2000) and A < 0 (e.g. ∼1980 to ∼1990) solar magnetic polarity cycles. With increasing perpendicular diffusion, the radial dependence of the computed electron spectra at distances with a large radial dependence was decreased but increased at distances with small radial dependence. Important is that a reduction in the latitudinal dependence of the differential intensities followed at all radial distances, with the largest effects in the inner heliosphere and at low energies.