Solar and Heliospheric Modulation of Cosmic Rays; Observational Constraints

Bernd Heber

Institut fur Experimentelle und Angewandte Physik, Christian Albrechts Universitat Kiel, Leibnizstr. 11, 24118 Kiel, Germany

Cosmic ray particles respond to the heliospheric magnetic field in the expanding solar wind and its turbulence and so provide a unique probe for conditions in the changing heliosphere. During the last decades the intensity time profiles have been provided by neutron monitors. Since the 1970ís the explorations of the heliosphere begun with spacecraft send to the outer heliosphere and solar Polar Regions. While the joint ESA/NASA-Ulysses mission revealed the three-dimensional behavior of cosmic rays in the inner heliosphere, the Pioneer and Voyager missions have greatly expanded our understanding of the structure and extent of the outer heliosphere. While this contribution concentrates on the observation, the talk by Ferreira will focus on numerical models describing the propagation of galactic cosmic rays as a sophisticated tool for interpreting and understanding these observations.