HR: 11:50h
AN: SH32A-07    [Abstracts]
TI: Ongoing Recovery of Anomalous Cosmic Rays at 1 AU and Decreasing Radial Intensity Gradients
AU: * Leske, R A
EM: ral@srl.caltech.edu
AF: California Institute of Technology, Mail Code 220-47, Pasadena, CA 91125, United States
AU: Cummings, A C
AF: California Institute of Technology, Mail Code 220-47, Pasadena, CA 91125, United States
AU: Cohen, C M
AF: California Institute of Technology, Mail Code 220-47, Pasadena, CA 91125, United States
AU: Mewaldt, R A
AF: California Institute of Technology, Mail Code 220-47, Pasadena, CA 91125, United States
AU: Stone, E C
AF: California Institute of Technology, Mail Code 220-47, Pasadena, CA 91125, United States
AU: Wiedenbeck, M E
AF: Jet Propulsion Laboratory, MS 169-327, Pasadena, CA 91109, United States
AU: von Rosenvinge, T T
AF: NASA/Goddard Space Flight Center, Code 661, Greenbelt, MD 20771, United States
AB: Using the Solar Isotope Spectrometer (SIS) on NASA's ACE spacecraft, we have measured the composition and energy spectra of anomalous cosmic rays (ACRs) near 1 AU down to energies of ~10 MeV/nucleon since late 1997. Recently these measurements have been augmented by data from the Low Energy Telescope (LET) on each of the two STEREO spacecraft, which allow us to extend the energy spectra down to ~3 MeV/nucleon. As solar minimum modulation conditions return, ACR intensities at 1 AU are recovering, although they are still a factor of ~5 lower than their peak intensities in 1997. Also, during the present A<0 magnetic polarity cycle their intensities are significantly lower relative to galactic cosmic rays (GCRs) than they were during the last A>0 cycle. We present updated measurements of the variation of the ACR oxygen intensity at 1 AU throughout the solar cycle. By comparing with observations from Voyager 1 and 2 in the outer heliosphere, we estimate the large-scale intensity gradients of ACR oxygen and GCR carbon at solar maximum, solar minimum, and during the ongoing recovery, and we investigate the role of drifts and convective processes in ACR modulation. This work was supported by NASA under grants NAG5-12929, NAS5-03131, and contract NAS7-03001.
DE: 2100 INTERPLANETARY PHYSICS
DE: 2104 Cosmic rays
DE: 2114 Energetic particles (7514)
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2007 Joint Assembly