Thermal-to-nonthermal element abundances in different Galactic environments
July 06, 2021
The nonthermal source abundances of elements play a crucial role in the understanding of cosmic ray phenomena from a few GeV up to several tens of EeV. In this work a first systematic approach is shown that describes the change of the abundances from the thermal to the nonthermal state via non-linear diffusive shock acceleration by a temporally evolving shock. Hereby, not only time-dependent ionization states of elements contained in the ambient gas are considered, but also elements condensed on solid, charged dust grains which can be injected into the acceleration process as well. This generic parametrized model is then applied to the case of particle acceleration by supernova remnants in various ISM phases as well as Wolf-Rayet (WR) wind environments. We show that the overall low energy cosmic ray (LECR) distribution by WR explosions yield a significantly harder, which makes this contribution quite promising in order to explain the spectral hardening of the observed LECR flux of certain elements, such as helium, at rigidities of about 1 TV.
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