Measurement of cosmic-ray proton and helium spectra during the 1987 solar minimum

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Abstract

view Abstract Citations (136) References (51) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Measurement of Cosmic-Ray Proton and Helium Spectra during the 1987 Solar Minimum Seo, E. S. ; Ormes, J. F. ; Streitmatter, R. E. ; Stochaj, S. J. ; Jones, W. V. ; Stephens, S. A. ; Bowen, T. Abstract The differential cosmic-ray proton and helium spectra have been measured during the 1987 solar minimum using a balloon-borne superconducting magnetic spectrometer launched from Prince Albert, Canada. The changing geomagnetic cutoff along the balloon trajectory was observed in the low-energy proton data to be about 25 percent below the nominal calculated values. The absolute particle fluxes were approximately equal to the highest fluxes observed at the previous solar minimum in 1977. Above 10 GV the observed spectra are represented by a power law in rigidity with spectral indices of 2.74 + or - 0.02 for protons and 2.68 + or - 0.03 for helium. The measurements above 200 MeV per nucleon are consistent with rigidity power-law interstellar spectra modulated with the solar modulation parameter phi = 500 MV. The energy dependence of the proton-to-helium ratio is consistent with rigidity power-law injection spectra and rigidity-dependent propagation without reacceleration. Publication: The Astrophysical Journal Pub Date: September 1991 DOI: 10.1086/170477 Bibcode: 1991ApJ...378..763S Keywords: Cosmic Rays; Energy Spectra; Helium; Particle Acceleration; Protons; Balloon Flight; Balloon-Borne Instruments; Spectrometers; Space Radiation; COSMIC RAYS: GENERAL; PARTICLE ACCELERATION full text sources ADS |

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