Wiedenbeck, M. E. and Christian, E. R. and Cohen, C. M. S. and Cummings, A. C. and Leske, R. A. and Mewaldt, R. A. and Slocum, P. L. and Stone, E. C. and von Rosenvinge, T. T. (2000) Enhanced Abundances of ^3He in Large Solar Energetic Particle Events. In: Acceleration and Transport of Energetic Particles Observed in the Heliosphere. AIP Conference Proceedings. No.528. American Institute of Physics , Melville, N.Y., pp. 107-110. ISBN 1-56396-951-3 http://resolver.caltech.edu/CaltechAUTHORS:20111216-080137898
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Observations of a number of relatively large solar energetic particle (SEP) events that have occurred since the launch of ACE in August 1997 have shown that the ratio of ^3He/^4He can be enhanced over the solar wind value (~4×10^(–4)) by more than an order of magnitude in such events. Since particle acceleration in these "gradual" SEP events is thought to be caused by CME-driven shocks traveling through the solar corona and interplanetary medium, a source of ^3He in addition to the solar wind appears required to provide the seed material. Using data from the Solar Isotope Spectrometer on ACE, we have carried out a more detailed investigation of the characteristics of the ^3He enhancements at energies >5 MeV/nucleon in three large SEP events (4 Nov 1997, 6 May 1998, and 14 Nov 1998). We find that the ^3He/^4He ratios are essentially time-independent during the events, that the ^3He energy spectra are markedly harder than those commonly observed in impulsive events, and that the spectra of ^3He may be harder than those of ^4He.
|Item Type:||Book Section|
|Additional Information:||© 2000 American Institute of Physics. Issue Date: 15 September 2000. This research was supported by the National Aeronautics and Space Administration at the California Institute of Technology (under grant NAG5-6912), the Jet Propulsion Laboratory, and the Goddard Space Flight Center.|
|Group:||Space Radiation Laboratory|
|Subject Keywords:||solar cosmic ray particles, cosmic ray composition, helium, isotope relative abundance, cosmic ray energy spectra, cosmic ray propagation, solar wind, acceleration|
|Classification Code:||PACS: 96.40.De; 95.85.Ry|
|Official Citation:||Enhanced abundances of [sup 3]He in large solar energetic particle events M. E. Wiedenbeck, E. R. Christian, C. M. S. Cohen, A. C. Cummings, R. A. Leske, R. A. Mewaldt, P. L. Slocum, E. C. Stone, and T. T. von Rosenvinge, AIP Conf. Proc. 528, 107 (2000), DOI:10.1063/1.1324290|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||16 Dec 2011 17:10|
|Last Modified:||26 Dec 2012 14:37|
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