A Cosmic Ray Signature of Equatorial Coronal Holes

The evolution of open field regions on the Sun over the last cycle is illustrated by observations of coronal holes in SOHO EIT images. The development of a large equatorial coronal hole near solar minimum is discussed, indicating the processes which led to the appearance of open field regions at low latitude. The observed cosmic ray signature is presented and interpreted in terms of the passage of the Earth through the streamer belt, which at this time had become distorted by the coronal hole and associated active region. The times when such equatorial coronal holes might be expected to directly influence cosmic ray counts in this way are seen to be limited to the approach to solar minimum, around minimum and the approach to maximum. This revised version was published online in August 2006 with corrections to the Cover Date.