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AGU: Journal of Geophysical Research, Space Physics

 

Keywords

  • Energetic particles

Index Terms

  • Interplanetary Physics: Energetic particles
  • Interplanetary Physics: Cosmic rays
  • Interplanetary Physics: Corotating streams
  • Interplanetary Physics: Interplanetary magnetic fields
Abstract
Cited By (4)
 

Abstract

Energetic particle observations by Ulysses during the declining phase of solar cycle 23

O. E. Malandraki

Research and Scientific Support Department of ESA, ESTEC, Noordwijk, Netherlands

R. G. Marsden

Research and Scientific Support Department of ESA, ESTEC, Noordwijk, Netherlands

C. Tranquille

Research and Scientific Support Department of ESA, ESTEC, Noordwijk, Netherlands

R. J. Forsyth

The Blackett Laboratory, Imperial College of Science and Technology, London, England

H. A. Elliott

Space Science and Engineering, Southwest Research Institute, San Antonio, Texas, USA

L. J. Lanzerotti

Center for Solar-Terrestrial Research, New Jersey Institute of Technology, Newark, New Jersey, USA

Bell Laboratories, Lucent Technologies, Murray Hill, New Jersey, USA

A. Geranios

Nuclear and Physics Department, University of Athens, Athens, Greece

We present recent energetic particle measurements from 1–20 MeV/n recorded by the Ulysses/COSPIN/LET instrument from mid-October to the end of November 2003 and from May 2004 to the end of February 2005. Long-lasting periods with enhanced solar activity occurred during the declining phase of the current solar cycle contributing to the high-intensity particle events and heavy ion signatures observed by Ulysses near the ecliptic plane, at ∼5 AU from the Sun. The energetic particles injected from the Sun during the January 2005 intense solar activity were not observed at Ulysses until a stream interface that acted as a barrier for the particles reached the spacecraft. Our observations during this period thus show that the propagation of energetic particles is largely governed by the existence of large-scale solar wind structures that impede the transport of the particles. We use the elemental composition of the particle fluxes recorded by COSPIN/LET to gain insight into the possible origin of the particle events. We study and provide a possible interpretation of the composition signatures observed at ∼5 AU during periods of CME/CIR combinations. Although predominantly SEP-like, the observed composition showed evidence for enhancements in He, which we suggest is of interstellar origin, consistent with CIR shocks accelerating ions from multiple sources.

Received 26 May 2006; accepted 1 February 2007; published 21 June 2007.

Citation: Malandraki, O. E., R. G. Marsden, C. Tranquille, R. J. Forsyth, H. A. Elliott, L. J. Lanzerotti, and A. Geranios (2007), Energetic particle observations by Ulysses during the declining phase of solar cycle 23, J. Geophys. Res., 112, A06111, doi:10.1029/2006JA011876.

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