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30th International Cosmic Ray Conference

3-11 July 2007
Merida, Mexico
Mexico/General timezone
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Contribution Poster

Merida, Mexico - Regency (Hyatt)
SH.2.1
Posters 1 + Coffee

Determination of ICME Geometry and Orientation from Ground Based Observations of Galactic Cosmic Rays

Speakers

  • Dr. Takao KUWABARA

Primary authors

  • Dr. Takao KUWABARA (Bartol Research Institute and Department of Physics and Astronomy, University of Delaware)

Co-authors

  • John BIEBER (Bartol Research Institute and Department of Physics and Astronomy, University of Delaware)
  • Paul EVENSON (Bartol Research Institute and Department of Physics and Astronomy, University of Delaware)
  • Kazuoki MUNAKATA (Department of Physics, Shinshu University)
  • Shin-ichi YASUE (School of General Education, Shinshu University)
  • Chihiro KATO (Department of Physics, Shinshu University)
  • Zenjiro FUJII (STE Laboratory, Nagoya University)
  • Marcus DULDIG (Australian Antarctic Division)
  • John HUMBLE (School of Mathematics and Physics, University of Tasmania)
  • Marlos SILVA (National Institute for Space Research)
  • Trivedi NALIN (National Institute for Space Research)
  • Walter GONZALEZ (National Institute for Space Research)
  • Alisson LAGO (National Institute for Space Research)
  • Nelson SCHUCH (Southern Regional Space Research Center - CRS/INPE)

Files

Abstract content

We have developed a method for determining ICME (Interplanetary coronal mass ejection) geometry from galactic cosmic ray data recorded by the ground- based muon detector network. The cosmic ray density depression inside the ICME, which is the cause of a Forbush decrease, is represented as an expanding cylinder based on a theoretical model of the cosmic ray particle diffusion. ICME geometry and orientation are deduced from observed time variations of density and density gradient, and are compared with that deduced from a magnetic flux rope model. From March 2001 to May 2005, 11 ICME events that produced Forbush decreases >2% were observed, and clear variations of the density gradient due to ICME passage were observed in 8 of 11 events. In 3 of these 8 events, clear signatures of magnetic flux rope structure (large, smooth rotation of magnetic field) were also seen, and the ICME geometry and orientation deduced from the two methods were very similar. This suggests that the cosmic ray-based method may provide a more robust method for deducing ICME geometry than the flux rope method for events where a large Forbush decrease is observed.

Reference

Proceedings of the 30th International Cosmic Ray Conference; Rogelio Caballero, Juan Carlos D'Olivo, Gustavo Medina-Tanco, Lukas Nellen, Federico A. Sánchez, José F. Valdés-Galicia (eds.); Universidad Nacional Autónoma de México, Mexico City, Mexico, 2008; Vol. 1 (SH), pages 335-338