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Ann. Geophys., 26, 1029-1037, 2008
www.ann-geophys.net/26/1029/2008/
© European Geosciences Union 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
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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