GALACTIC COSMIC-RAY ENERGY SPECTRA AND COMPOSITION DURING THE 2009-2010 SOLAR MINIMUM PERIOD

Journal Article · Thu Jun 20 00:00:00 EDT 2013 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/770/2/117· OSTI ID:22127077

Lave, K. A.; Binns, W. R.; Israel, M. H. ^[1]; Wiedenbeck, M. E. ^[2]; Christian, E. R.; De Nolfo, G. A.; Von Rosenvinge, T. T. ^[3]; Cummings, A. C.; Davis, A. J.; Leske, R. A.; Mewaldt, R. A.; Stone, E. C. ^[4]

---

1. Department of Physics and the McDonnell Center for the Space Sciences, Washington University, St. Louis, MO 63130 (United States)
2. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)
3. NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
4. California Institute of Technology, Pasadena, CA 91125 (United States)

We report new measurements of the elemental energy spectra and composition of galactic cosmic rays during the 2009-2010 solar minimum period using observations from the Cosmic Ray Isotope Spectrometer (CRIS) onboard the Advanced Composition Explorer. This period of time exhibited record-setting cosmic-ray intensities and very low levels of solar activity. Results are given for particles with nuclear charge 5 {<=} Z {<=} 28 in the energy range {approx}50-550 MeV nucleon{sup -1}. Several recent improvements have been made to the earlier CRIS data analysis, and therefore updates of our previous observations for the 1997-1998 solar minimum and 2001-2003 solar maximum are also given here. For most species, the reported intensities changed by less than {approx}7%, and the relative abundances changed by less than {approx}4%. Compared with the 1997-1998 solar minimum relative abundances, the 2009-2010 abundances differ by less than 2{sigma}, with a trend of fewer secondary species observed in the more recent time period. The new 2009-2010 data are also compared with results of a simple ''leaky-box'' galactic transport model combined with a spherically symmetric solar modulation model. We demonstrate that this model is able to give reasonable fits to the energy spectra and the secondary-to-primary ratios B/C and (Sc+Ti+V)/Fe. These results are also shown to be comparable to a GALPROP numerical model that includes the effects of diffusive reacceleration in the interstellar medium.

• OSTI ID: 22127077
• Journal Information: Astrophysical Journal, Vol. 770, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ABUNDANCE
ATOMIC NUMBER
COMPARATIVE EVALUATIONS
COSMIC RADIATION
DATA ANALYSIS
ENERGY SPECTRA
GALAXIES
MEV RANGE
NUCLEONS
SOLAR ACTIVITY
SPECTROMETERS
SPHERICAL CONFIGURATION
SUN
TRANSPORT THEORY