Inferring Energetic Particle Mean Free Paths from Observations of Anomalous Cosmic Rays in the Outer Heliosphere at Solar Maximum
We find that the mean free pathlength is higher by a factor of 10 or more at solar minimum than at the last solar maximum in 1900-1991, consistent with previous findings. In 2000-2001, the mean free pathlength has declined by a factor of ~10, but is still larger by a factor of ~3.6 than its value of ~0.15 AU in 1990-1991. As solar maximum conditions become durably established in the outer heliosphere over the next few months, it may be possible to deduce the radial dependence of the mean free pathlength.
Additional Information© Copernicus GmbH. Provided by the NASA Astrophysics Data System This work was supported by NASA under contract NAS7-918. We thank the Wllcox Solar Observatory for the he-1 iospheric ti lt values (http://quake.stanford.edu/ wso/wso.html). We thank the MTT Space Plasma Group for supplying the daily averaged IMP-8 solar wind speeds (ftp://space.mit.edu/pub/plasma/imp/www/imp.html). We thank the ACE/SWEPAM team for supplying the ACE solar wind speeds (hltp://www.srl .cal tech .cdu/ ACE/ ASC/level2/i ndex .htm I).
Published - 2001-16.pdf