Earth, Planets and Space

, Volume 57, Issue 11, pp 1083–1091 | Cite as

Sharply concentrated cosmic-ray excess fluxes from heliomagnetospheric nose and tail boundaries observed with neutron monitors on the ground

  • K. Nagashima
  • I. Kondo
  • Z. Fujii
Open Access


Two kinds of sharply concentrated excess flux of cosmic rays from heliomagnetospheric nose and tail directions (right ascension α ∼ 18 hours and ∼ 6 hours) are found by the analysis of sidereal daily variation of neutron intensity (median energy Em ∼ 20 GeV) on the ground. These fluxes do not show any response to the polarity reversal of solar magnetic field at the north pole and is contradictory to the simulation of the solar modulation of galactic anisotropy, which produces sidereal variation at the Earth greater in the negative polarity state than in the positive state. This indicates that they are not of the galactic origin and would be produced on the heliomagnetospheric nose and tail boundaries where it is considered that the interaction between the galactic and solar magnetic fields could produce the cosmic-ray acceleration. The acceleration mechanism producing the polarity-independent sidereal variation against solar modulation will be discussed.


Cosmic-ray sidereal anisotropy heliomagnetosphere (HMS) polarity of HMS solar modulation 


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Copyright information

© The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences. 2005

Authors and Affiliations

  1. 1.Solar-Terrestrial Environment LaboratoryNagoya UniversityNagoyaJapan
  2. 2.Institute for Cosmic Ray ResearchUniversity of TokyoKashiwaJapan

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