Cosmic Ray Drifts at Solar Maximum

Abstract

A fully time-dep endent cosmic ray modulation model, based on the numerical solution of Parker's transport equation, is used to study the amount of particle drifts needed to explain the observed 2.5 GV electron to proton ratio (e/p) by the KET instrument on the Ulysses spacecraft. It is shown that the model successfully simulates the modulation of electrons and Helium ions for 11-year and 22-year cycles. It is based on the compound approach that incorporates the concept of propagation diffusion barriers combined with global increases in the heliospheric magnetic field when propagated from the Sun throughout the heliosphere, as well as drifts and the other basic modulation mechanisms. It is found that less than 10% drifts is needed at solar maximum, when the solar magnetic field reverses, to explain the observed e/p along the Ulysses trajectory.