Intensity Gradients of Anomalous Cosmic Rays Between 1 AU and Voyager During Solar Cycle 23
Using ACE/SIS data we obtain measurements of the variation of the anomalous cosmic ray (ACR) O intensity at 1 AU throughout the solar cycle, including periods near solar maximum. After being suppressed by a factor of ~100 or more from 2001 through 2003 during solar maximum, ACR intensities are once again recovering at 1 AU, but their intensities are lower relative to higher rigidity galactic cosmic rays (GCRs) than they were during entry into solar maximum in 1998-2000. Comparison of the 1 AU ACR and GCR time variations with those measured by both Voyager spacecraft in the outer heliosphere shows that both ACR and GCR large-scale radial gradients are greater at solar maximum than at solar minimum, and that the ACR radial gradients are much larger than those of the GCRs, becoming very large inside of ~5 AU.
Additional Information© 2005 Tata Institute of Fundamental Research. This work was supported by NASA at Caltech (under grants NAG5-6912 and NAS7-03001), JPL, and GSFC. We acknowledge the Ulysses Data System for COSPIN/LET data and the National Science Foundation (grant ATM-9912341) for Climax neutron monitor data.
Published - Stone_2005p113.pdf