HR: 1340h
AN: SH33A-1077    [Abstracts]
TI: The September 2004 Event at Ulysses and ACE: Influence of Large-Scale Interplanetary Structures on Energetic Particle Propagation
AU: * Lario, D
EM: david.lario@jhuapl.edu
AF: The Johns Hopkins University. Applied Physics Laboratory, 11100 Johns Hopkins Rd., Laurel, MD 20723, United States
AU: Decker, R B
EM: rob.decker@jhuapl.edu
AF: The Johns Hopkins University. Applied Physics Laboratory, 11100 Johns Hopkins Rd., Laurel, MD 20723, United States
AU: Malandraki, O E
EM: omaland@xan.duth.gr
AF: Research and Scientific Support Department. European Space Agency, Keplerlaan, 1, Noordwijk, NL-2200 AG, Netherlands
AU: Lanzerotti, L J
EM: louis.j.lanzerotti@njit.edu
AF: Bell Laboratories. Lucent Technologies, 600 Mountain Av., Murray Hill, NJ 07974, United States
AU: Lanzerotti, L J
EM: louis.j.lanzerotti@njit.edu
AF: Center for Solar-Terrestrial Research. New Jersey Institute of Technology, University Heights, Newark, NJ 07102, United States
AB: An intense solar energetic particle (SEP) event was detected in September 2004 by near-Earth spacecraft and by Ulysses at 5.4 AU. The characteristics of the intensity and anisotropy time profiles at both heliospheric locations were determined by the presence of a corotating low-density, low-speed, and low-proton-beta (β_p) solar wind stream. This low-β_p stream was followed by a faster and denser solar wind resulting in the formation of a strong compression region. The bulk part of SEPs at 1 AU was observed in the downstream region of this compression region. Only those SEPs either able to leak from behind the compression region or accelerated by the associated CME-driven shock as it penetrated into the low-β_p region, or both, were observed prior to the main component of the SEP event. Anisotropic ion intensity enhancements observed upstream of this shock most likely resulted from both particle acceleration in a corrugated shock surface and particle propagation within the low-β_p region. The particle event at Ulysses was exceptional in terms of the large and long-lasting (>4 days) field-aligned anisotropies. These large anisotropies resulted from both the leakage of energetic particles from behind the compression region and their propagation within the low-β_p region. We propose a scenario that explains the characteristics of the SEP event at both 1 AU and Ulysses. The effects that large-scale interplanetary structures have on the energetic particle transport determine the properties of the event at both spacecraft by modifying the time history of both particle intensities and anisotropies. These effects must be carefully considered by models of energetic particle transport in the heliosphere.
DE: 2102 Corotating streams
DE: 2114 Energetic particles (7514)
DE: 2139 Interplanetary shocks
DE: 2164 Solar wind plasma
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2007 Fall Meeting