skip to main content

SciTech ConnectSciTech Connect

Title: Explanation of the local galactic cosmic ray energy spectra measured by Voyager 1. I. Protons

Almost exactly 100 yr after the original discovery of cosmic rays, the V1 spacecraft has observed, for the first time, the local interstellar medium energy spectra of cosmic ray H, He, C/O nuclei at nonrelativistic kinetic energies, after leaving the heliosphere modulation region on 2012 August 25. We explain these observations by modeling the propagation of these particles in the local Galactic environment with an updated steady-state spatial diffusion model including all particle momentum losses with the local interstellar gas (Coulomb/ionization, pion production, adiabatic deceleration, and fragmentation interactions). Excellent agreement with the V1 cosmic ray H observations is obtained if the solar system resides within a spatially homogeneous layer of distributed cosmic ray sources injecting the same momentum power law ∝p {sup –s} with s = 2.24 ± 0.12. The best fit to the V1 H observations also provides an estimate of the characteristic break kinetic energy T{sub C} = 116 ± 27 MeV, representing the transition from ionization/Coulomb energy losses at low energies to pion production and adiabatic deceleration losses in a Galactic wind at high energies. As the determined value is substantially smaller than 217 MeV in the absence of adiabatic deceleration, our results prove the existence ofmore » a Galactic wind in the local Galactic environment.« less
Authors:
;  [1] ;  [2]
  1. Institut für Theoretische Physik, Lehrstuhl IV: Weltraum- und Astrophysik, Ruhr-Universität Bochum, D-44780 Bochum (Germany)
  2. Department of Astronomy, New Mexico State University, Las Cruces, NM 88003 (United States)
Publication Date:
OSTI Identifier:
22356864
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 787; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCELERATION; COSMIC RADIATION; COSMIC RAY SOURCES; COULOMB ENERGY; COULOMB IONIZATION; DIFFUSION; ENERGY SPECTRA; GALAXIES; HELIOSPHERE; INTERSTELLAR SPACE; MEV RANGE; PETROLEUM RESIDUES; SIMULATION; SOLAR SYSTEM; SPACE VEHICLES; STEADY-STATE CONDITIONS; STELLAR WINDS; VOYAGER SPACE PROBES