1994 Fiscal Year Final Research Report Summary
Origin of Anomalous Cosmic Rays and the Acceleration Mechanism
| Project/Area Number |
05640353
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
素粒子・核・宇宙線
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| Research Institution | Ehime University |
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Principal Investigator |
HASEBE Nobuyuki Ehime Univ., F.of Gen.Educ., Assoc.Prof., 教養部, 助教授 (10127904)
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| Co-Investigator(Kenkyū-buntansha) |
MISHIMA Yasushi Ehime Univ., F.of Science, Assoc.Prof., 理学部, 助教授 (50036191)
YOSHII Hisashi Ehime Univ., F.of Gen.Educ., Prof., 教養部, 教授 (00036360)
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| Project Period (FY) |
1993 – 1994
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| Keywords | Cosmic Ray / Anomalous Cosmic Rays / Elemental Abundance / Solar Wind Termination shock / Solar Modulation / Particle Acceleration |
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| Research Abstract |
We have measured cosmic ray particles during the period September 1992 through August 1994 using the particle telescopes MI-1/2 and HI onboard the GEOTAIL satellite orbiting at 1 AU.We have examined the quiet-time particles from He to Fe with the energies of 3-250 MeV/n. Remaekable enhancement of anomalous O,N and Ne in the energy spectra below 50 MeV/n was observed in the late 1992, just after the solar maximum. The anomalous Cis also evident though the C enhancement is small compared with them. The correlation between the anomalous cosmic ray data and the neutron monitor data is relatively good in the last two solar cycles but in the years 1992-1994 there is a large difference between the ACR and the neutron counting rate. The fluxes of O,N and Ne in this solar cycle have rapidly recovered to the level in the previous solar minimum although the origin of this rapid recovery of the ACR fluxes is presently unknown.
Strong presence of anomalous cosmic ray N,O and Ne was shown well before the approaching solar minimum at solar cycle 22. Anomalous Ar was firstly observed at 1 AU though it was observed by the VOYAGER in deep space. We found the first evidence for the emergence of a measurable sulfur component of anomalous cosmic rays below 30 MeV/n. Comparing the fluxes of anomalous N,O and Ne with high first ionization potentials (FIPs) , the anomalous C and S fluxes, which have intermediate FIPs, are very small. These results could be qualitatively expected from the scenario for the origin of the anomalous cosmic rays proposed by Fisk et al. (1974) . It implies that they are significantly ionized in the very local interstellar medium.
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