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  • 1
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    Galactic Cosmic-Ray Energy Spectra and Composition during the 2009-2010 Solar Minimum Period (2013)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: 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. 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 2sigma, 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.
    Keywords: Space Radiation
    Type: GSFC-E-DAA-TN10263 , The Astrophysical Journal (ISSN 0004-637X); 770; 2; 117; June 20, 2013
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  • 2
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    Constraints on Galactic Cosmic-Ray Origins from Elemental and Isotopic Composition Measurements (2013)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The most recent measurements by the Cosmic Ray Isotope Spectrometer (CRIS) aboard the Advanced Composition Explorer (ACE) satellite of ultra-heavy cosmic ray isotopic and elemental abundances will be presented. A range of isotope and element ratios, most importantly Ne-22/Ne-20, Fe-58/Fe-56, and Ga-31/Ge -32 show that the composition is consistent with source material that is a mix of approx 80% ISM (with Solar System abundances) and 20% outflow/ejecta from massive stars. In addition, our data show that the ordering of refractory and volatile elements with atomic mass is greatly improved when compared to an approx 80%/20% mix rather than pure ISM, that the refractory and volatile elements have similar slopes, and that refractory elements are preferentially accelerated by a factor of approx 4. We conclude that these data are consistent with an OB association origin of GCRs.
    Keywords: Space Radiation
    Type: GSFC-E-DAA-TN10609 , International Cosmic Ray Conference; Jul 02, 2013 - Jul 09, 2013; Rio de Janeiro; Brazil
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  • 3
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    The Energetic Trans-Iron Composition Experiment (ENTICE) on the Heavy Nuclei Explorer (HNX) Mission (2001)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: The ENTICE experiment is one of two instruments that make up the HNX mission. The experimental goal of ENTICE is to measure with high precision the elemental abundances of all nuclei with Z between 10 and 82. This will enable us to determine if the injection mechanism for the cosmic ray accelerator is controlled by FIP or Volatility and to study the mix of nucleosynthetic processes that contribute to the galactic cosmic ray source. The ENTICE experiment utilizes the dE/dx-C method of charge determination and consists of silicon dE/dx detectors, Cherenkov detectors with two different refractive indices, and a fiber hodoscope. We will describe the instrument and its performance based on beam tests of a prototype instrument.
    Keywords: Space Radiation
    Type: ICRC 2001 Conference; Aug 07, 2001 - Aug 15, 2001; Hamburg; Germany
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  • 4
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    The Energetic Trans-Iron Composition Experiment (ENTICE) on the Heavy Nuclei Explorer (HNX) (2001)
    In:  Other Sources
    Details
    Publication Date: 2019-07-17
    Description: The ENTICE experiment is one of two instruments which make up the HNX mission. The experimental goal of ENTICE is to measure with high precision the elemental abundances of all nuclei with 10〈=Z〈=82. This will enable us to distinguish between possible injection mechanisms for the galactic cosmic ray accelerator such-as those dependent upon volatility or first ionization potential, and to study the mix of nucleosynthetic processes that contribute to the galactic cosmic ray source. The ENTICE experiment utilizes the dE/dx-C method of charge determination and consists of silicon dE/dx detectors, Cherenkov detectors with two different refractive indices, and a scintillating fiber hodoscope. The geometrical factor of the instrument is 8m2.sr. We will present a description of the instrument and its expected performance based on beam tests and a balloon flight of a prototype instrument.
    Keywords: Space Radiation
    Type: International Cosmic Ray Conference; Aug 07, 2001 - Aug 15, 2001; Hamburg; Germany
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  • 5
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    Elemental GCR Observations during the 2009-2010 Solar Minimum Period (2013)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Using observations from the Cosmic Ray Isotope Spectrometer (CRIS) onboard the Advanced Composition Explorer (ACE), we present new measurements of the galactic cosmic ray (GCR) elemental composition and energy spectra for the species B through Ni in the energy range approx. 50-550 MeV/nucleon during the record setting 2009-2010 solar minimum period. These data are compared with our observations from the 1997-1998 solar minimum period, when solar modulation in the heliosphere was somewhat higher. For these species, we find that the intensities during the 2009-2010 solar minimum were approx. 20% higher than those in the previous solar minimum, and in fact were the highest GCR intensities recorded during the space age. Relative abundances for these species during the two solar minimum periods differed by small but statistically significant amounts, which are attributed to the combination of spectral shape differences between primary and secondary GCRs in the interstellar medium and differences between the levels of solar modulation in the two solar minima. We also present the secondary-to-primary ratios B/C and (Sc+Ti+V)/Fe for both solar minimum periods, and demonstrate that these ratios are reasonably well fit by a simple "leaky-box" galactic transport model that is combined with a spherically symmetric solar modulation model.
    Keywords: Space Radiation
    Type: GSFC-E-DAA-TN10268 , International Cosmic Ray Conference; Jul 02, 2013 - Jul 09, 2013; Rio de Janeiro,Brazil; Brazil
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