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Title: Possible evidence for the stochastic acceleration of secondary antiprotons by supernova remnants

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Publication Date:
Sponsoring Org.:
OSTI Identifier:
Grant/Contract Number:
FG02-13ER41958; AC02-07CH11359
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Physical Review D
Additional Journal Information:
Journal Volume: 95; Journal Issue: 12; Related Information: CHORUS Timestamp: 2017-06-14 22:12:18; Journal ID: ISSN 2470-0010
American Physical Society
Country of Publication:
United States

Citation Formats

Cholis, Ilias, Hooper, Dan, and Linden, Tim. Possible evidence for the stochastic acceleration of secondary antiprotons by supernova remnants. United States: N. p., 2017. Web. doi:10.1103/PhysRevD.95.123007.
Cholis, Ilias, Hooper, Dan, & Linden, Tim. Possible evidence for the stochastic acceleration of secondary antiprotons by supernova remnants. United States. doi:10.1103/PhysRevD.95.123007.
Cholis, Ilias, Hooper, Dan, and Linden, Tim. 2017. "Possible evidence for the stochastic acceleration of secondary antiprotons by supernova remnants". United States. doi:10.1103/PhysRevD.95.123007.
title = {Possible evidence for the stochastic acceleration of secondary antiprotons by supernova remnants},
author = {Cholis, Ilias and Hooper, Dan and Linden, Tim},
abstractNote = {},
doi = {10.1103/PhysRevD.95.123007},
journal = {Physical Review D},
number = 12,
volume = 95,
place = {United States},
year = 2017,
month = 6

Journal Article:
Free Publicly Available Full Text
This content will become publicly available on June 14, 2018
Publisher's Accepted Manuscript

Citation Metrics:
Cited by: 4works
Citation information provided by
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  • The antiproton-to-proton ratio in the cosmic-ray spectrum is a sensitive probe of new physics. Using recent measurements of the cosmic-ray antiproton and proton fluxes in the energy range of 1-1000 GeV, we study the contribution to themore » $$\bar{p}/p$$ ratio from secondary antiprotons that are produced and subsequently accelerated within individual supernova remnants. We consider several well-motivated models for cosmic-ray propagation in the interstellar medium and marginalize our results over the uncertainties related to the antiproton production cross section and the time-, charge-, and energy-dependent effects of solar modulation. We find that the increase in the $$\bar{p}/p$$ ratio observed at rigidities above $$\sim$$ 100 GV cannot be accounted for within the context of conventional cosmic-ray propagation models, but is consistent with scenarios in which cosmic-ray antiprotons are produced and subsequently accelerated by shocks within a given supernova remnant. In light of this, the acceleration of secondary cosmic rays in supernova remnants is predicted to substantially contribute to the cosmic-ray positron spectrum, accounting for a significant fraction of the observed positron excess.« less
  • Molecular observations can be used to place strong constraints on the point of origin and the spectrum of cosmic rays in the vicinity of o Per in the Per OB2 association. We argue that stochastic acceleration by the second-order Fermi effect in the nearly fully ionized supernova remnant associated with the region will produce cosmic rays of precisely the correct characteristics.
  • Using three-dimensional magnetohydrodynamic simulations, we investigate general properties of a blast wave shock interacting with interstellar clouds. The pre-shock cloudy medium is generated as a natural consequence of the thermal instability that simulates realistic clumpy interstellar clouds and their diffuse surrounding. The shock wave that sweeps the cloudy medium generates a turbulent shell through the vorticity generations that are induced by shock-cloud interactions. In the turbulent shell, the magnetic field is amplified as a result of turbulent dynamo action. The energy density of the amplified magnetic field can locally grow comparable to the thermal energy density, particularly at the transitionmore » layers between clouds and the diffuse surrounding. In the case of a young supernova remnant (SNR) with a shock velocity {approx}> 10{sup 3} km s{sup -1}, the corresponding strength of the magnetic field is approximately 1 mG. The propagation speed of the shock wave is significantly stalled in the clouds because of the high density, while the shock maintains a high velocity in the diffuse surrounding. In addition, when the shock wave hits the clouds, reflection shock waves are generated that propagate back into the shocked shell. From these simulation results, many observational characteristics of the young SNR RX J1713.7-3946 that is suggested to be interacting with molecular clouds can be explained as follows. The reflection shocks can accelerate particles in the turbulent downstream region where the magnetic field strength reaches 1 mG, which causes short-time variability of synchrotron X-rays. Since the shock velocity is stalled locally in the clouds, the temperature in the shocked cloud is suppressed far below 1 keV. Thus, thermal X-ray line emission would be faint even if the SNR is interacting with molecular clouds. We also find that the photon index of the {pi}{sup 0}-decay gamma rays generated by cosmic-ray protons can be 1.5 (corresponding energy flux is {nu}F{sub {nu}}{proportional_to}{nu}{sup 0.5}) because the penetration depth of high-energy particles into the clumpy clouds depends on their energy. This suggests that, if we rely only on the spectral study, the hadronic gamma-ray emission is indistinguishable from the leptonic inverse Compton emission. We propose that the spatial correlation of the gamma-ray, X-ray, and CO line-emission regions can be conclusively used to understand the origin of gamma rays from RX J1713.7-3946.« less
  • Recent gamma-ray observations of middle-aged supernova remnants revealed a mysterious broken power-law spectrum. Using three-dimensional magnetohydrodynamic simulations, we show that the interaction between a supernova blast wave and interstellar clouds formed by thermal instability generates multiple reflected shocks. The typical Mach numbers of the reflected shocks are shown to be M{approx_equal} 2 depending on the density contrast between the diffuse intercloud gas and clouds. These secondary shocks can further energize cosmic-ray particles originally accelerated at the blast-wave shock. This 'two-step' acceleration scenario reproduces the observed gamma-ray spectrum and predicts the high-energy spectral index ranging approximately from 3 to 4.
  • An attempt is made to determine whether or not the structure of supernova remnant shells is dependent on the angle between the line of sight and the Galactic magnetic field and if this structure can be explained either by quasi-parallel or quasi-perpendicular acceleration. The method used to determine the line of sight angles to the magnetic field is described. A model for the emissivity of a supernova remnant is developed. 46 references.