HR: 09:30h
AN: SH11A-07    [Abstracts]
TI: Energy Spectra of Energetic Particles Upstream of the Termination Shock
AU: * Jokipii, J R
EM: jokipii@lpl.arizona.edu
AF: University of Arizona Planetary Sciences, Kuiper Space Sciences, Tucson, AZ 85721, United States
AU: Giacalone, J
EM: giacalon@lpl.arizona.edu
AF: University of Arizona Planetary Sciences, Kuiper Space Sciences, Tucson, AZ 85721, United States
AU: Decker, R B
EM: robert.decker@jhuapl.edu
AF: Applied Physics Lab Johns Hopkins University, 11100 Johns Hopkins Rd, Laurel, MD 20723-6099, United States
AB: Energetic particles observed upstream of the solar-wind termination shock provide valuable remote information concerning physical processes occurring at the shock. In this paper we discuss the implications of the energy spectra of ions observed at Voyagers 1 and 2, for the energy range .04-18 MeV, for the time periods when the spacecraft were upstream of the shock but very close to it. The upstream events at the two Voyagers were similar in many respects in that they were highly variable and anisotropic. However, the Voyager 2 spectra exhibit an evolving low-energy turnover at approximately 1 MeV, whereas the Voyager 1 spectra do not show any such turnover. This asymmetry in the behavior at the two spacecraft is likely to be a manifestation of a large-scale spatial asymmetry of the heliosphere and/or the termination shock. We present possible interpretations of the observed energy spectra in terms of the propagation of the particles from the shock to the spacecraft, in the stochastic upstream magnetic field, and a blunt, asymmetric termination shock. The interpretations are consistent with the observations and allow us to place limits on the large-scale shape and any lateral asymmetries of the shock. They also constrains the propagation modes of the energetic particles.
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