Observations of the Van Allen Radiation Belt, Solar Wind and Corotating Interaction Regions during Solar Minimum

Fast moving streams from coronal holes can interact with slower downstream solar wind (SW) to form co-rotating interaction regions (CIRs). The CIRs can be very effective in producing variations in the outer zone of the Van Allen radiation belt (RB). This effect is particularly noticeable during solar minimum when there is little other solar activity. In this study, we use a combination of THEMIS and GOES radiation belt observations, STEREO images and SW data from 2008 and 2009 to analyze the relationships among individual features on the Sun, SW parameters, and variations in outer zone RB relativistic electrons. Variations in the RB outer zone relativistic fluxes are often observed during times of persistent trans-equatorial coronal holes during solar minimum. During solar minimum, the likelihood of CIRs forming by 1 AU increases if the interacting regions appear at low solar latitudes. We will discuss the solar wind conditions that correlate with changes in outer zone RB fluxes during solar minimum and how these conditions relate to trans-equatorial coronal holes and active regions.