Corotating interaction regions

Abstract

Corotating Interaction Regions are long lasting large-scale plasma structures generated in low and middle latitude regions of the heliosphere by the interaction of a stable fast solar wind stream with the surrounding slow solar wind. Associated with these plasma structures are recurrent MeV-ion events and recurrent decreases of the galactic and anomalous cosmic ray intensities. Prior to the Ulysses-mission the effect of corotating interaction regions could only be observed at low or moderate heliographic latitudes. The three-dimensional extent and their role in structuring the quiet heliosphere became clear after Ulysses high latitude observations had became available. Corotating interaction regions possibly play a role in determining solar modulation of galactic and anomalous cosmic rays during periods of low to moderate solar activity. In March 1996, April 1997, and June 1998 two workshops on Development and Effects of Corotating Interaction Regions were held at Elmau Castle, Germany, and at the International Space Science Institute in Bern, Switzerland, primarily based on new high latitude observations from Ulysses and considering as well in-ecliptic and outer-heliospheric spacecraft result. In this paper MeV-particle, galactic and anomalous cosmic ray as well as plasma observations from spacecraft in the inner heliosphere will be presented.