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....

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Bibliographic Details
Published in:The Astrophysical journal 2014-05, Vol.787 (1), p.1-8
Main Authors: Schlickeiser, R, Webber, W R, Kempf, A
Format: Article
Language:English
Subjects:
ACCELERATION
Adiabatic flow
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
COSMIC RADIATION
COSMIC RAY SOURCES
Cosmic rays
COULOMB ENERGY
Coulomb friction
COULOMB IONIZATION
Deceleration
DIFFUSION
ENERGY SPECTRA
Galactic winds
GALAXIES
HELIOSPHERE
Interstellar gas
INTERSTELLAR SPACE
Ionization
Kinetic energy
MEV RANGE
PETROLEUM RESIDUES
Pions
SIMULATION
SOLAR SYSTEM
SPACE VEHICLES
STEADY-STATE CONDITIONS
STELLAR WINDS
VOYAGER SPACE PROBES
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Summary: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 [is proportional to] p super(-s) with s = 2.24 + or - 0.12. The best fit to the V1 H observations also provides an estimate of the characteristic break kinetic energy T sub(C) = 116 + or - 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 of a Galactic wind in the local Galactic environment.
ISSN:0004-637X
1538-4357
DOI:10.1088/0004-637X/787/1/35