The heliospheric modulation of galactic cosmic rays at solar minimum

Abstract

The observations acquired by the Ulysses spacecraft since launch, but especially during the recent fast latitude scan, have provided a comprehensive, 3-dimensional view of the inner heliosphere. Together with the observations by IMP 8, Pioneer 10 and the two Voyagers, a wealth of new observations on particles and fields enables us to improve significantly our understanding of the modulation of cosmic rays and the anomalous component in the heliosphere. In this publication a number of these interesting modulation features e.g. the recovery towards solar minimum modulation and its time-dependence, the latitudinal gradients and rigidity dependence of the latitude effect, the apparent north-south asymmetry in heliospheric modulation and charge dependence are discussed in the context of numerical model predictions and how these observations have influenced the way the modeling is done presently. For the purpose of this review, the emphasis is on the modulation of galactic protons and electrons with energies > ~100 MeV.