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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 26, issue 4
Ann. Geophys., 26, 1029–1037, 2008
https://doi.org/10.5194/angeo-26-1029-2008
© Author(s) 2008. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 26, 1029–1037, 2008
https://doi.org/10.5194/angeo-26-1029-2008
© Author(s) 2008. This work is distributed under
the Creative Commons Attribution 3.0 License.

  13 May 2008

13 May 2008

Energetic particle measurements from the Ulysses/COSPIN/LET instrument obtained during the August/September 2005 events

O. E. Malandraki1,*,**, R. G. Marsden1, C. Tranquille1, R. J. Forsyth2, H. A. Elliott3, and A. Geranios4 O. E. Malandraki et al.
  • 1Research and Scientific Support Department of ESA, ESTEC, Noordwijk, The Netherlands
  • 2The Blackett Laboratory, Imperial College of Science and Technology, London, UK
  • 3Space Science and Engineering, Southwest Research Institute, San Antonio, TX, USA
  • 4Nuclear and Particle Physics Department, University of Athens, Athens, Greece
  • *currently at: The Blackett Laboratory, Imperial College of Science and Technology, London, UK
  • **also at: Institute for Astronomy and Astrophysics, National Observatory of Athens, Athens, Greece

Abstract. We report recent observations of energetic particles at energies 1–40 MeV/n made by the COSPIN/LET instrument onboard the Ulysses spacecraft during the period of intense solar activity in August/September 2005 during the declining phase of solar cycle 23. Ulysses, having started its climb to high southern latitudes for the third time, was located at ~5 AU, at a helio-latitude of ~30 degrees south. It detected the arrival of a solar wind compound stream resulting from the merging of a series of fast halo CMEs ejected from the Sun in late August and early September 2005 and their interaction with the pre-existing pattern of solar wind Stream Interaction Regions (SIRs) in the ambient medium through which they propagated. The heavy ion intensities are observed by COSPIN/LET to remain elevated for at least 20 days following the very intense X17.0/3B solar flare on 7 September and its associated very fast CME (plane of sky projected CME speed ~2400 km s−1). We carry out an analysis of the composition of the particle increases observed at the location of the spacecraft. Although the composition signatures were predominantly Solar Energetic Particle (SEP)-like, after the passage of the compound stream over Ulysses, in association with a characteristic forward and reverse shock pair, the observations showed evidence of an enhanced He content.

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