The first observation of sulfur in anomalous cosmic rays by the Geotail and the wind spacecrafts

T. Takashima*, T. Doke, T. Hayashi, J. Kikuchi, M. Kobayashi, H. Shirai, N. Takehana, M. Ehara, Y. Yamada, S. Yanagita, Nobuyuki Hasebe, T. Kashiwagi, C. Kato, K. Munakata, T. Kohno, K. Kondoh, H. Murakami, A. Nakamoto, T. Yanagimachi, D. V. ReamesT. T. Von Rosenvinge

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)


The Geotail high-energy particle instruments have observed cosmic-ray particles in the energy range from 3 MeV n-1 to 150 MeV n-1 at 1 AU during the period 1992 September-1995 August. A remarkable enhancement of anomalous cosmic-ray (ACR) N, O, Ne, and C is observed during the period. A measurable enhancement of the sulfur flux below about 20 MeV n-1 was observed. This is the first evidence showing the existence of sulfur in the anomalous component. The flux increase of anomalous sulfur, with a first ionization potential (FIP) of 10.4 eV, is smaller than that of ACR carbon with an FIP of 11.3 eV and much smaller than those of high-FIP elements, which suggests that the fractions of neutral carbon and sulfur atoms are significantly low in the very local interstellar medium.

Original languageEnglish
JournalAstrophysical Journal
Issue number2 PART II
Publication statusPublished - 1997
Externally publishedYes


  • Cosmic rays
  • ISM: general

ASJC Scopus subject areas

  • Space and Planetary Science


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