Transient variations in cosmic ray proton fluxes from BESS-Polar I

N. Thakur, K. Abe, H. Fuke, S. Haino, T. Hams, A. Itazaki, K. C. Kim, T. Kumazawa, M. H. Lee, Y. Makida, S. Matsuda, K. Matsumoto, J. W. Mitchell, Z. Myers, J. Nishimura, M. Nozaki, R. Orito, J. F. Ormes, M. Sasaki, E. S. SeoY. Shikaze, R. E. Streitmatter, J. Suzuki, Y. Takasugi, K. Takeuchi, K. Tanaka, T. Yamagami, A. Yamamoto, T. Yoshida, K. Yoshimura

Research output: Contribution to conferencePaperpeer-review


BESS (Balloon-borne Experiment with a Superconducting Spectrometer) had its first circumpolar flight from Williams Field near McMurdo Station, Antarctica from Dec. 13 to 21, 2004. Our sub-1% precision reveals BESS-Polar I proton fluxes exhibit transient variations at the few1% level. The time progression of proton flux has three main features; a rising flux at the beginning of the flight, a transition region around Dec. 17, followed by quasi-periodic variation. Neutron monitor data show that the BESS-Polar I flight occurred during the recovery phase of a small Forbush decrease. The solar wind plasma and particle data show that this flight took place during the tail end of a high-energy, multiple-eruption solar energetic particle (SEP) event. A high speed solar wind stream arrived near the Earth around Dec. 17, 2004. We present the flux progression as a function of energy between 0.1 - 100.0 GeV and suggest possible physical interpretations.

Original languageEnglish
Number of pages4
Publication statusPublished - 2011
Externally publishedYes
Event32nd International Cosmic Ray Conference, ICRC 2011 - Beijing, China
Duration: Aug 11 2011Aug 18 2011


Other32nd International Cosmic Ray Conference, ICRC 2011


  • BESS-polar I
  • CIR
  • Diurnal variations
  • Proton fluxes
  • Short-term variations
  • Turbulent interaction regions

ASJC Scopus subject areas

  • Nuclear and High Energy Physics


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