HR: 1340h
AN: SH53B-0322    [Abstracts]
TI: A Loss-Cone Precursor of an Approaching Shock Observed by a Cosmic-Ray Muon Hodoscope at Mt. Norikura
AU: * Munakata, K
EM: kmuna00@gipac.shinshu-u.ac.jp
AF: Physics Department, Shinshu University, 3-1-1 Asahi, Matsumoto, 390-8621 Japan
AU: Kuwabara, T
EM: t02h107@amail.shinshu-u.ac.jp
AF: Physics Department, Shinshu University, 3-1-1 Asahi, Matsumoto, 390-8621 Japan
AU: Yasue, S
EM: shyasue@gipac.shinshu-u.ac.jp
AF: Physics Department, Shinshu University, 3-1-1 Asahi, Matsumoto, 390-8621 Japan
AU: Kato, C
EM: ckato@corona.shinshu-u.ac.jp
AF: Physics Department, Shinshu University, 3-1-1 Asahi, Matsumoto, 390-8621 Japan
AU: Ohashi, Y
EM: y1ohashi@fa.mbn.or.jp
AF: Institute for Cosmic Ray Research, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, 277-8582 Japan
AU: Okada, A
EM: okada@icrr.u-tokyo.ac.jp
AF: Institute for Cosmic Ray Research, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, 277-8582 Japan
AU: Aoki, T
EM: aoki@icrr.u-tokyo.ac.jp
AF: Institute for Cosmic Ray Research, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, 277-8582 Japan
AU: Mitsui, K
EM: mitsuik@ygu.ac.jp
AF: Faculty of Management Information, Yamanashi Gakuin University, 1203-12, Katakura-cho, Hachioji, 192-0914 Japan
AU: Kojima, H
EM: hkojima@nagoya-wu.ac.jp
AF: Nagoya Women's University, 3-40 Shioji-cho, Mizuho-ku, Nagoya, 467-8610 Japan
AU: Bieber, J
EM: john@bxclu.bartol.udel.edu
AF: Bartol Research Institute, University of Delaware, Newark, DE 19716 United States
AU: Evenson, P
EM: penguin@bartol.udel.edu
AF: Bartol Research Institute, University of Delaware, Newark, DE 19716 United States
AB: We analyze a loss-cone anisotropy observed by a ground-based muon hodoscope at Mt. Norikura in Japan for 7 hours preceding the arrival of interplanetary shock at Earth on October 28, 2003. The observed anisotropy can be well reproduced with a model taking account of the directional distribution of cosmic ray intensity in space, the average rigidity dependence of Forbush decrease region formed behind the shock and the rigidity dependence of the lead-time of the precursory anisotropy. Best-fitting a model to the observed anisotropy suggests that the loss-cone in this event has rather broad pitch-angle distribution from the IMF. According to numerical simulations of high-energy particle transport across the shock, this implies that the shock is _gquasi-parallel_h shock in which the angle between the magnetic field and the shock normal is small. It is also suggested that the lead-time of this precursor rapidly decreases with decreasing rigidity. It is 10 hours at 30 GV for muon detectors, while it is only 1.4 hours at 10 GV for neutron monitors. We also estimate the parallel mean free path of pitch angle scattering to shorter than that predicted from the representative power spectrum of IMF turbulence. This implies that the IMF is much more turbulent in this event than that characterized by the representative power spectrum.
DE: 2104 Cosmic rays
DE: 2111 Ejecta, driver gases, and magnetic clouds
DE: 2114 Energetic particles, heliospheric (7514)
DE: 2118 Energetic particles, solar
DE: 2164 Solar wind plasma
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2004 AGU Fall Meeting