Cosmic Rays in the Heliosphere

In every scientific discipline there are milestones - periods of significant accom­ plishment when it is appropriate to pause and summarize the state of the field. Such is the case for the study of the behavior of cosmic rays in the heliosphere. We are just passing through solar minimum conditions, when the heliosphere has a well-ordered and relatively simple configuration. We have been fortunate to have an array of spacecraft - unprecedented in the history of space exploration and unlikely to be repeated for generations - to provide comprehensive measurements of cosmic rays throughout the heliosphere. Ulysses has completed its historic first exploration of the heliosphere at high heliographic latitudes. Pioneer and Voyager have been exploring the outer heliosphere. The durable IMP-8 and now the WIND spacecraft have provided detailed baseline measurements at Earth. Concurrently, there has been a steady improvement in theoretical understanding of cosmic ray behavior through the use of ever more sophisticated numerical models. This milestone in cosmic ray studies was celebrated with a Workshop on Cos­ mic Rays in the Heliosphere which was convened by L. A. Fisk, J. R. Jokipii.