12-20 July 2017
BEXCO
Asia/Seoul timezone
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Contribution

BEXCO - Room A(101/102)

[CRD008] What Shapes the Energy Spectra of Galactic Cosmic Rays in the Local Interstellar Medium?

Speakers

  • Alan CUMMINGS

Primary authors

Co-authors

Description

The Voyager 1 energy spectra of cosmic ray elements in the local interstellar medium (LISM) and models of interstellar propagation that fit these data and which also fit the data taken at 1 AU at high energies (Cummings et al., Astrophys. J., 2016) show a roll over from a power-law at high energies to a broad peak at lower energies. The break in the high-energy power law occurs at approximately 1 GeV/nuc. We examine one of the GALPROP propagation models to investigate the roles of different physical processes in the roll over of the spectra at lower energies. We find that within the context of a GALPROP plain diffusion model, a significant portion of the roll over is due to ionization energy losses, as expected. However, we find that other processes also contribute to the roll over, such as the rigidity dependence of the assumed injection spectrum and the rigidity dependence of the assumed diffusion coefficient in interstellar space. Although these assumed dependences may be incorrect, we conclude that it is unlikely that ionization energy losses alone account for the shape of the energy spectra. Other possibilities that could cause part of the roll over include a galactic wind or some form of momentum diffusion. This work was supported by NASA under contract NNN12AA01C.