Please use this identifier to cite or link to this item: http://hdl.handle.net/2289/7263
Title: Can a cosmic ray carrot explain the ionization level in diffuse molecular clouds?
Authors: Recchia, S.
Phan, V. H. M.
Biswas, Sayan
Gabici, S.
Keywords: ISM: clouds
cosmic rays
ISM: magnetic fields
Issue Date: May-2019
Publisher: Oxford University Press on behalf of the Royal Astronomical Society
Citation: Monthly Notices of the Royal Astronomical Society, 2019, Vol.485, p2276–2280
Abstract: Low-energy cosmic rays are the major ionization agents of molecular clouds. However, it has been shown that, if the cosmic ray spectrum measured by Voyager 1 is representative of the whole Galaxy, the predicted ionization rate in diffuse clouds fails to reproduce data by 1–2 orders of magnitude, implying that an additional source of ionization must exist. One of the solutions proposed to explain this discrepancy is based on the existence of an unknown low-energy (in the range 1 keV–1 MeV, not probed by Voyager) cosmic ray component, called carrot when first hypothesized by Reeves and collaborators in the seventies. Here we investigate the energetic required by such scenario. We show that the power needed to maintain such low-energy component is comparable of even larger than that needed to explain the entire observed cosmic ray spectrum. Moreover, if the interstellar turbulent magnetic field has to sustain a carrot, through second-order Fermi acceleration, the required turbulence level would be definitely too large compared to the one expected at the scale resonant with such low-energy particles. Our study basically rules out all the plausible sources of a cosmic ray carrot, thus making such hidden component unlikely to be an appealing and viable source of ionization in molecular clouds.
Description: Open Access
URI: http://hdl.handle.net/2289/7263
ISSN: 0035-8711
1365-2966 - (online)
Alternative Location: https://ui.adsabs.harvard.edu/abs/2019MNRAS.485.2276R/abstract
https://arxiv.org/abs/1901.04912
https://doi.org/10.1093/mnras/stz555
Copyright: 2019 The Author(s)
Appears in Collections:Research Papers (A&A)

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