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Published April 15, 1984 | Published
Journal Article Open

Elemental composition of solar energetic particles


The Low Energy Telescopes on the Voyager spacecraft have been used to measure the elemental composition (2 ≤ Z ≤ 28) and energy spectra (5-15 MeV per nucleon) of solar energetic particles (SEPs) in seven large flare events. Four flare events were selected which have SEP abundance ratios approximately independent of energy per nucleon. For these selected flare events, SEP composition results may be described by an average composition plus a systematic flare-to-flare deviation about the average. The four-flare average SEP composition is systematically different from the solar composition determined by photospheric spectroscopy. These systematic composition differences are apparently not due to SEP propagation or acceleration effects. In contrast, the four-flare average SEP composition is in agreement with measured solar wind abundances and with a number of recent spectroscopic coronal abundance measurements. These findings suggest that SEPs originate in the corona, and that both SEPs and the solar wind sample a coronal composition which is significantly and persistently different from that measured for the photosphere. Our observations thus provide a measure of the coronal abundances of 15 elements.

Additional Information

© 1984 The American Astronomical Society. Received 1983 June 27; accepted 1983 October 3. We gratefully acknowledge the contributions of the Voyager CRS team, consisting of scientists and engineers at the California Institute of Technology, the Goddard Space Flight Center, the University of Arizona, and the University of New Hampshire. We especially thank Dr. R. A. Mewaldt for his ideas, comments, and continuing interest. This work has been supported in part by the National Aeronautics and Space Administration under contract NAS7-918 and grant NGR 05-002-160.

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Published - 1984ApJ___279__827C.pdf


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