scholarly journals Diffusive Shock Acceleration of High Energy Cosmic Rays

2004 ◽  
Vol 136 ◽  
pp. 198-207 ◽  
Author(s):  
Matthew G. Baring
Keyword(s):  
Cosmic Rays ◽  
High Energy ◽  
Shock Acceleration ◽  
Diffusive Shock Acceleration ◽  
High Energy Cosmic Rays

scholarly journals Particle acceleration in the superwinds of starburst galaxies

2018 ◽  
Vol 616 ◽  
pp. A57 ◽  
Author(s):  
G. E. Romero ◽  
A. L. Müller ◽  
M. Roth
Keyword(s):  
Cosmic Rays ◽  
Galactic Disk ◽  
Cosmic Ray ◽  
High Energy ◽  
Shock Acceleration ◽  
Spectral Energy ◽  
Starburst Galaxy ◽  
Diffusive Shock Acceleration ◽  
Mass Load ◽  
The Galaxy

Context. Starbursts are galaxies undergoing massive episodes of star formation. The combined effect of stellar winds from hot stars and supernova explosions creates a high-temperature cavity in the nuclear region of these objects. The very hot gas expands adiabatically and escapes from the galaxy creating a superwind which sweeps matter from the galactic disk. The superwind region in the halo is filled with a multi-phase gas with hot, warm, cool, and relativistic components. Aims. The shocks associated with the superwind of starbursts and the turbulent gas region of the bubble inflated by them might accelerate cosmic rays up to high energies. In this work we calculate the cosmic ray production associated with the superwind using parameters that correspond to the nearby southern starburst galaxy NGC 253, which has been suggested as a potential accelerator of ultra-high-energy cosmic rays. Methods. We evaluate the efficiency of both diffusive shock acceleration (DSA) and stochastic diffusive acceleration (SDA) in the superwind of NGC 253. We estimate the distribution of both hadrons and leptons and calculate the corresponding spectral energy distributions of photons. The electromagnetic radiation can help to discriminate between the different scenarios analyzed. Results. We find that the strong mass load of the superwind, recently determined through ALMA observations, strongly attenuates the efficiency of DSA in NGC 253, whereas SDA is constrained by the age of the starburst. Conclusions. We conclude that NGC 253 and similar starbursts can only accelerate iron nuclei beyond ~1018 eV under very special conditions. If the central region of the galaxy harbors a starved supermassive black hole of ~106 M⊙, as suggested by some recent observations, a contribution in the range 1018−1019 eV can be present for accretion rates ṁ ~ 10−3 in Eddington units. Shock energies of the order of 100 EeV might only be possible if very strong magnetic field amplification occurs close to the superwind.

scholarly journals Monte Carlo Simulations of Particle Acceleration at Oblique Shocks

1994 ◽  
Vol 142 ◽  
pp. 547-552
Author(s):  
Matthew G. Baring ◽  
Donald C. Ellison ◽  
Frank C. Jones
Keyword(s):  
Monte Carlo ◽  
Mach Number ◽  
Cosmic Rays ◽  
Monte Carlo Simulations ◽  
Cosmic Ray ◽  
Heavy Ion ◽  
High Energy ◽  
Shock Acceleration ◽  
High Energy Cosmic Rays ◽  
Cosmic Ray Acceleration

AbstractThe Fermi shock acceleration mechanism may be responsible for the production of high-energy cosmic rays in a wide variety of environments. Modeling of this phenomenon has largely focused on plane-parallel shocks, and one of the most promising techniques for its study is the Monte Carlo simulation of particle transport in shocked fluid flows. One of the principal problems in shock acceleration theory is the mechanism and efficiency of injection of particles from the thermal gas into the accelerated population. The Monte Carlo technique is ideally suited to addressing the injection problem directly, and previous applications of it to the quasi-parallel Earth bow shock led to very successful modeling of proton and heavy ion spectra, as well as other observed quantities. Recently this technique has been extended to oblique shock geometries, in which the upstream magnetic field makes a significant angle ΘB1 to the shock normal. In this paper, spectral results from test particle Monte Carlo simulations of cosmic-ray acceleration at oblique, nonrelativistic shocks are presented. The results show that low Mach number shocks have injection efficiencies that are relatively insensitive to (though not independent of) the shock obliquity, but that there is a dramatic drop in efficiency for shocks of Mach number 30 or more as the obliquity increases above 15°. Cosmic-ray distributions just upstream of the shock reveal prominent bumps at energies below the thermal peak; these disappear far upstream but might be observable features close to astrophysical shocks.Subject headings: acceleration of particles — cosmic rays — shock waves

scholarly journals The Origins of High-Energy Cosmic Rays

1994 ◽  
Vol 142 ◽  
pp. 937-944
Author(s):  
W. I. Axford
Keyword(s):  
Energy Spectrum ◽  
Cosmic Rays ◽  
Active Galactic Nuclei ◽  
Supernova Remnants ◽  
Galactic Nuclei ◽  
High Energy ◽  
Shock Acceleration ◽  
Acceleration Of Particles ◽  
Intermediate Region ◽  
High Energy Cosmic Rays

AbstractOur current understanding of acceleration processes for Galactic and extragalactic cosmic rays is briefly reviewed. Shock acceleration in supernova remnants remains the most favored process for cosmic rays up to the “knee” of the all-particle total energy spectrum at 1014 - 1015 eV. The highest energy particles are almost certainly extragalactic, and the most favored sources are associated with active galactic nuclei in one way or another. The intermediate region between rigidities of 1014 and 1018 V is more difficult to understand, although a galactic origin is preferred at present. The problem of making a smooth join in the spectrum at the knee suggests that these particles should not be considered to be independent of those at lower energies.Subject headings: acceleration of particles — cosmic rays — shock waves

MULTI-MESSENGER ASTRONOMY WITH CENTAURUS A

2009 ◽  
Vol 18 (10) ◽  
pp. 1591-1595 ◽  
Author(s):  
M. KACHELRIEß ◽  
S. OSTAPCHENKO ◽  
R. TOMÀS
Keyword(s):  
Cosmic Rays ◽  
High Energy ◽  
Shock Acceleration ◽  
Primary Proton ◽  
Ultrahigh Energy ◽  
High Energy Part ◽  
Hadronic Interactions ◽  
High Energy Cosmic Rays ◽  
The Core ◽  
Centaurus A

We calculated for the nearest active galactic nucleus (AGN), Centaurus A (Cen A), the flux of high energy cosmic rays and of accompanying secondary photons and neutrinos expected from hadronic interactions in the source. We used as two basic models for the generation of ultrahigh energy cosmic rays (UHECR) shock acceleration in the radio jet and acceleration in the regular electromagnetic field close to the core of the AGN, normalizing the UHECR flux to the observations of the Auger experiment. Here we compare the previously obtained photon fluxes with the recent data reported by the Fermi LAT and H.E.S.S. collaborations. In the case of the core model, we find good agreement both for the predicted spectral shape and the overall normalization between our earlier results and the H.E.S.S. observations for a primary proton energy dN/dE ∝ E-α with α ~ 2 or smaller. A broken power law with high-energy part α = -2.7 leads to photon fluxes in excess of the Fermi measurements. The energy spectrum of the photon fluxes obtained by us for the jet scenario is in all cases at variance with the H.E.S.S. and Fermi observations.

scholarly journals Planck Neutrinos as Ultra High Energy Cosmic Rays

2020 ◽  
Vol 29 (1) ◽  
pp. 40-46
Author(s):  
Dmitri L. Khokhlov
Keyword(s):  
Black Holes ◽  
Cosmic Rays ◽  
Standard Model ◽  
Active Galactic Nuclei ◽  
Planck Scale ◽  
Galactic Nuclei ◽  
High Energy ◽  
Ultra High Energy ◽  
High Energy Cosmic Rays ◽  
The Standard Model

AbstractThe studied conjecture is that ultra high energy cosmic rays (UHECRs) are hypothetical Planck neutrinos arising in the decay of the protons falling onto the gravastar. The proton is assumed to decay at the Planck scale into positron and four Planck neutrinos. The supermassive black holes inside active galactic nuclei, while interpreted as gravastars, are considered as UHECR sources. The scattering of the Planck neutrinos by the proton at the Planck scale is considered. The Planck neutrinos contribution to the CR events may explain the CR spectrum from 5 × 1018 eV to 1020 eV. The muon number in the Planck neutrinos-initiated shower is estimated to be larger by a factor of 3/2 in comparison with the standard model that is consistent with the observational data.

scholarly journals Starburst galaxies strike back: a multi-messenger analysis with Fermi-LAT and IceCube data

2021 ◽  
Vol 503 (3) ◽  
pp. 4032-4049
Author(s):  
Antonio Ambrosone ◽  
Marco Chianese ◽  
Damiano F G Fiorillo ◽  
Antonio Marinelli ◽  
Gennaro Miele ◽  
...  
Keyword(s):  
Cosmic Rays ◽  
Gamma Ray ◽  
Neutrino Flux ◽  
Data Interpretation ◽  
Realistic Model ◽  
High Energy ◽  
Starburst Galaxies ◽  
Neutrino Factory ◽  
High Energy Cosmic Rays ◽  
Astrophysical Objects

ABSTRACT Starburst galaxies, which are known as ‘reservoirs’ of high-energy cosmic-rays, can represent an important high-energy neutrino ‘factory’ contributing to the diffuse neutrino flux observed by IceCube. In this paper, we revisit the constraints affecting the neutrino and gamma-ray hadronuclear emissions from this class of astrophysical objects. In particular, we go beyond the standard prototype-based approach leading to a simple power-law neutrino flux, and investigate a more realistic model based on a data-driven blending of spectral indexes, thereby capturing the observed changes in the properties of individual emitters. We then perform a multi-messenger analysis considering the extragalactic gamma-ray background (EGB) measured by Fermi-LAT and different IceCube data samples: the 7.5-yr high-energy starting events (HESE) and the 6-yr high-energy cascade data. Along with starburst galaxies, we take into account the contributions from blazars and radio galaxies as well as the secondary gamma-rays from electromagnetic cascades. Remarkably, we find that, differently from the highly-constrained prototype scenario, the spectral index blending allows starburst galaxies to account for up to $40{{\ \rm per\ cent}}$ of the HESE events at $95.4{{\ \rm per\ cent}}$ CL, while satisfying the limit on the non-blazar EGB component. Moreover, values of $\mathcal {O}(100\, \mathrm{PeV})$ for the maximal energy of accelerated cosmic-rays by supernovae remnants inside the starburst are disfavoured in our scenario. In broad terms, our analysis points out that a better modelling of astrophysical sources could alleviate the tension between neutrino and gamma-ray data interpretation.

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