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, Koji Yoshimura

Research output: Chapter in Book/Report/Conference proceedingConference contribution


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
Title of host publicationProceedings of the 32nd International Cosmic Ray Conference, ICRC 2011
PublisherInstitute of High Energy Physics
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

Cite this

Thakur, N., Abe, K., Fuke, H., Haino, S., Hams, T., Itazaki, A., Kim, K. C., Kumazawa, T., Lee, M. H., Makida, Y., Matsuda, S., Matsumoto, K., Mitchell, J. W., Myers, Z., Nishimura, J., Nozaki, M., Orito, R., Ormes, J. F., Sasaki, M., ... Yoshimura, K. (2011). Transient variations in cosmic ray proton fluxes from BESS-Polar I. In Proceedings of the 32nd International Cosmic Ray Conference, ICRC 2011 (Vol. 11, pp. 220-223). Institute of High Energy Physics.