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Cosmic ray energy loss in the heliosphere: Direct evidence from electron-capture-decay secondary isotopes

Niebur, S. M. and Scott, L. M. and Wiedenbeck, M. E. and Binns, W. R. and Christian, E. R. and Cummings, A. C. and Davis, A. J. and George, J. S. and Hink, P. L. and Israel, M. H. and Leske, R. A. and Mewaldt, R. A. and Stone, E. C. and von Rosenvinge, T. T. and Yanasak, N. E. (2003) Cosmic ray energy loss in the heliosphere: Direct evidence from electron-capture-decay secondary isotopes. Journal of Geophysical Research A, 108 (A10). Art. No. 8033. ISSN 0148-0227. https://resolver.caltech.edu/CaltechAUTHORS:20140826-164919486

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Abstract

Measurements by the Cosmic Ray Isotope Spectrometer (CRIS) on the Advanced Composition Explorer (ACE) spacecraft provide direct evidence that galactic cosmic rays lose energy as a result of their interactions with magnetic fields expanding with the solar wind. The secondary isotopes ^(49)V and ^(51)Cr can decay to ^(49)Ti and ^(51)V, respectively, only by electron capture. The observed abundances of these isotopes are directly related to the probability of attaching an electron from the interstellar medium; this probability decreases strongly with increasing energy around a few hundred MeV/nucleon. At the highest energies observed by CRIS, electron attachment on these nuclides is very unlikely, and thus ^(49)V and ^(51)Cr are essentially stable. At lower energies, attachment and decay do occur. Comparison of the energy dependence of the daughter/parent ratios ^(49)Ti/^(49)V and ^(51)V/^(51)Cr during solar minimum and solar maximum conditions confirms that increased energy loss occurs during solar maximum. This analysis indicates an increase in the modulation parameter ϕ of about 400 to 700 MV corresponding to an increase in average energy loss for these elements of about 200 to 300 MeV/nucleon.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1029/2003JA009876DOIArticle
http://onlinelibrary.wiley.com/doi/10.1029/2003JA009876/abstractPublisherArticle
ORCID:
AuthorORCID
Wiedenbeck, M. E.0000-0002-2825-3128
Binns, W. R.0000-0001-6110-3407
Christian, E. R.0000-0003-2134-3937
Cummings, A. C.0000-0002-3840-7696
Israel, M. H.0000-0002-8104-208X
Leske, R. A.0000-0002-0156-2414
Mewaldt, R. A.0000-0003-2178-9111
Stone, E. C.0000-0002-2010-5462
Additional Information:© 2003 The American Geophysical Union. Received 31 January 2003; Revised 3 April 2003; Accepted 17 April 2003; Published 19 August 2003. This research was supported by NASA grant NAG5-6912 to the California Institute of Technology and by related NASA grants or subcontracts to the Jet Propulsion Laboratory, Goddard Space Flight Center, and Washington University. Shadia Rifai Habbal thanks Thomas Gaisser and L. A. Fisk for their assistance in evaluating this paper.
Group:Space Radiation Laboratory
Funders:
Funding AgencyGrant Number
NASANAG5-6912
Subject Keywords:cosmic ray isotopes; solar modulation; adiabatic energy loss; electron-capture decay
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Space Radiation Laboratory2003-52
Issue or Number:A10
Record Number:CaltechAUTHORS:20140826-164919486
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20140826-164919486
Official Citation:Niebur, S. M., Scott, L. M., Wiedenbeck, M. E., Binns, W. R., Christian, E. R., Cummings, A. C., . . . Yanasak, N. E. (2003). Cosmic ray energy loss in the heliosphere: Direct evidence from electron-capture-decay secondary isotopes. Journal of Geophysical Research: Space Physics, 108(A10), 8033. doi: 10.1029/2003ja009876
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:48952
Collection:CaltechAUTHORS
Deposited By: Joanne McCole
Deposited On:27 Aug 2014 18:04
Last Modified:09 Mar 2020 13:19

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