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

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 similar to 50-550 MeV nucleon(-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. Formost species, the reported intensities changed by less than similar to 7%, and the relative abundances changed by less than similar to 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 BC 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.