HR: 09:15h
AN: SH11A-06    [Abstracts]
TI: Evolution of the Energy Spectra of Low-Energy Particles at Voyagers 1 and 2 in the Outer Heliosphere and Implications for the Source Location of Anomalous Cosmic Rays
AU: * Cummings, A C
EM: ace@srl.caltech.edu
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: McDonald, F B
AF: University of Maryland, Computer and Space Science Bldg 3245, College Park, MD 20742, United States
AU: Heikkila, B C
AF: Goddard Space Flight Center, Code 612.4, Greenbelt, MD 20771, United States
AU: Lal, N
AF: Goddard Space Flight Center, Code 612.4, Greenbelt, MD 20771, United States
AU: Webber, W R
AF: New Mexico State University, P.O. Box 30001/Dept. 4500, Las Cruces, NM 88003, United States
AB: As of this writing, 4 September 2007, the Voyager 1 (V1) spacecraft is at 103.8 AU and 34.3 deg N. It is in the heliosheath, presumably about 10 AU beyond the solar wind termination shock. The Voyager 2 (V2) spacecraft is at 83.7 AU and 27.5 deg S. It has not crossed the termination shock but may be close, having been observing low-energy termination shock particles since ~2005.0. In addition, very recently the intensity of protons with ~2-8 MeV at V2 has grown to exceed that at V1 by a factor of ~3. From ~10 to 100 MeV, the V2 intensity is lower than that at V1. For He, from ~10-25 MeV/nuc, the V2 energy spectrum is below that of V1 but well above that at V1 when it crossed the shock in late 2004. Energy spectra at both spacecraft have recently been evolving. The spectral observations at V2 when it crosses the termination shock compared to the spectra at V1 at the same time and at the time V1 crossed may help determine the source location of the anomalous cosmic rays. Finally, the energy spectra of H and O scale to that of He with multiplicative factors in energy/nucleon and intensity that suggest that the diffusion coefficient is proportional to particle speed times rigidity to the power ~1.4. This work was supported by NASA under contract NAS7-03001.
DE: 2104 Cosmic rays
DE: 2114 Energetic particles (7514)
DE: 2124 Heliopause and solar wind termination
DE: 2126 Heliosphere/interstellar medium interactions
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2007 Fall Meeting