The modelling of the latitude dependence of cosmic ray protons and electrons in the inner heliosphere

Observations during the fast latitude scan of Ulysses show that the latitude dependence of cosmic ray protons is significantly less than predicted by drift models which were based on the Parker geometry for the heliospheric magnetic field (HMF) and diffusion coefficients ∞ 1/Bp. Recent modeling with a modified HMF and enhanced turbulence in the polar zones of the heliosphere can reproduce the observed latitude dependence for protons reasonably well at high rigidities. It is shown here that incorporating enhanced perpendicular diffusion in the polar direction in a drift model also gives a latitude dependence for protons, over a wide range of rigidities, and a latitude dependence for electrons and therefore a charge-dependence that are compatible with observations. © 1997 COSPAR. Published by Elsevier Science Ltd.