Cosmic ray energy loss in the heliosphere

Direct evidence from electron-capture-decay secondary isotopes

S. M. Niebur, L. M. Scott, M. E. Wiedenbeck, W. R. Binns, E. R. Christian, A. C. Cummings, A. Davis, J. S. George, P. L. Hink, M. H. Israel, R. A. Leske, R. A. Mewaldt, E. C. Stone, T. T. Von Rosenvinge, Nathan Eugene Yanasak

Research output: Contribution to journalArticle

10 Citations (Scopus)

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 49V and 51Cr can decay to 49Ti and 51V, 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 49V and 51Cr are essentially stable. At lower energies, attachment and decay do occur. Comparison of the energy dependence of the daughter/parent ratios 49Ti/49V and 51V/51Cr 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.

Original languageEnglish (US)
Article number8033
JournalJournal of Geophysical Research: Space Physics
Volume108
Issue numberA10
DOIs
StatePublished - Jan 1 2003

Fingerprint

Cosmic rays
heliosphere
electron capture
Isotopes
cosmic ray
cosmic rays
isotopes
Energy dissipation
energy dissipation
deterioration
electrons
isotope
electron
Electrons
energy
decay
Spectrometers
Solar wind
spectrometers
Advanced Composition Explorer

Keywords

  • Adiabatic energy loss
  • Cosmic ray isotopes
  • Electron-capture decay
  • Solar modulation

ASJC Scopus subject areas

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

Cite this

Cosmic ray energy loss in the heliosphere : Direct evidence from electron-capture-decay secondary isotopes. / Niebur, S. M.; Scott, L. M.; Wiedenbeck, M. E.; Binns, W. R.; Christian, E. R.; Cummings, A. C.; Davis, A.; George, J. S.; Hink, P. L.; Israel, M. H.; Leske, R. A.; Mewaldt, R. A.; Stone, E. C.; Von Rosenvinge, T. T.; Yanasak, Nathan Eugene.

In: Journal of Geophysical Research: Space Physics, Vol. 108, No. A10, 8033, 01.01.2003.

Research output: Contribution to journalArticle

Niebur, SM, Scott, LM, Wiedenbeck, ME, Binns, WR, Christian, ER, Cummings, AC, Davis, A, George, JS, Hink, PL, Israel, MH, Leske, RA, Mewaldt, RA, Stone, EC, Von Rosenvinge, TT & Yanasak, NE 2003, 'Cosmic ray energy loss in the heliosphere: Direct evidence from electron-capture-decay secondary isotopes', Journal of Geophysical Research: Space Physics, vol. 108, no. A10, 8033. https://doi.org/10.1029/2002JE001868
Niebur, S. M. ; Scott, L. M. ; Wiedenbeck, M. E. ; Binns, W. R. ; Christian, E. R. ; Cummings, A. C. ; Davis, A. ; George, J. S. ; Hink, P. L. ; Israel, M. H. ; Leske, R. A. ; Mewaldt, R. A. ; Stone, E. C. ; Von Rosenvinge, T. T. ; Yanasak, Nathan Eugene. / Cosmic ray energy loss in the heliosphere : Direct evidence from electron-capture-decay secondary isotopes. In: Journal of Geophysical Research: Space Physics. 2003 ; Vol. 108, No. A10.
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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 49V and 51Cr can decay to 49Ti and 51V, 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 49V and 51Cr are essentially stable. At lower energies, attachment and decay do occur. Comparison of the energy dependence of the daughter/parent ratios 49Ti/49V and 51V/51Cr 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.",
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