HR: 1330h
AN: SH23A-03    [Abstracts]
TI: Three Possible Energetic Particle Sources at the Termination Shock
AU: * Hill, M E
EM: mehill@umd.edu
AF: Department of Physics, University of Maryland, College Park, MD 20742-4111 United States
AU: Hamilton, D C
AF: Department of Physics, University of Maryland, College Park, MD 20742-4111 United States
AU: Lipman, M D
AF: Department of Physics, University of Maryland, College Park, MD 20742-4111 United States
AU: Decker, R B
AF: Applied Physics Laboratory, Johns Hopkins University, Laurel, MD 20723 United States
AU: Krimigis, S M
AF: Applied Physics Laboratory, Johns Hopkins University, Laurel, MD 20723 United States
AB: As we approach mid-2005, we mark the end of three years during which Voyager 1 (V1) witnessed extraordinary particle events as it traveled through a region, beyond 85 AU from the Sun, which is strongly influenced by the solar wind termination shock (TS). V1 has traveled 10 AU since entering this region and appears to be near the TS throughout. This suggests either that there is a chance relationship between the speed of V1 and that of the expanding TS or that this TS-dominated region is large, but variable. We report on up to three populations of energetic particles observed in this region, with sources at the termination shock. (1) Above 40 MeV is the classical anomalous cosmic ray (ACR) component, accelerated across the global TS. The ACR intensities are modulated at lower energies, forming a spectral peak---an unmistakable feature of transport---but exhibit only small variations during this period. (2) Particles from ~50 keV -- 40 MeV have intense, falling shock-accelerated spectra that vary greatly throughout this period and show no evidence of transport down to ~50 keV. Therefore, it appears that V1 is intermittently magnetically connected to a nearby region of the TS, which is the source of these particles. (3) There is evidence of a third particle population, which may be due to particles accelerated at a nearby deformation of the shock with a local radius of curvature that is much smaller than that of the global TS. This population's source appears not to be magnetically connected and is distant enough for transport effects to be obvious, but the small radius of curvature results in a spectral peak at ~5 MeV, well below that of classical ACRs.
UR: http://space.umd.edu/voyager
DE: 2104 Cosmic rays
DE: 2114 Energetic particles, heliospheric (7514)
DE: 2124 Heliopause and solar wind termination
DE: 7851 Shock waves
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2005 Joint Assembly