scholarly journals Extragalactic shocks as cosmic accelerators

2006 ◽  
Vol 2 (14) ◽  
pp. 95-96
Author(s):  
Mikhail V. Medvedev
Keyword(s):  
Active Galactic Nuclei ◽  
Large Scale ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
High Energy ◽  
Maximum Energy ◽  
Shock Acceleration ◽  
Fermi Acceleration ◽  
High Energy Cosmic Rays ◽  
Relativistic Shocks

AbstractIt is quite well established that shocks accelerate particles via the Fermi mechanism. We discuss common features of various extragalactic sources, ranging from Gamma-Ray Bursts and jets of Active Galactic Nuclei to Large-Scale Structure shocks and address how they affect particle acceleration. In particular, we address constraints on the maximum energy of ultra-high-energy cosmic rays. Interestingly, some recent studies indicate that Fermi acceleration in relativistic shocks (and GRBs, in particular) faces severe difficulties. We will address this issue and demonstrate that the ‘observed’ shock acceleration of electrons may have nothing to do with Fermi acceleration, but may rather be associated with micro-physics of collisionless shocks.

scholarly journals Active Galactic Nuclei: Jets as the Source of Hadrons and Neutrinos

2014 ◽  
Vol 1 (1) ◽  
pp. 269-273
Author(s):  
Athina Meli ◽  
Paolo Ciarcelluti
Keyword(s):  
Active Galactic Nuclei ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
Cosmic Ray ◽  
High Energy ◽  
Plasma Jets ◽  
Shock Acceleration ◽  
Fermi Acceleration ◽  
Acceleration Mechanism ◽  
Relativistic Shocks

Active galactic nuclei are extragalactic sources, and their relativistic hot-plasma jets are believed to be the main candidates of the cosmic-ray origin, above the so-called knee region of the cosmic-ray spectrum. Relativistic shocks, either single or multiple, have been observed or been theorized to be forming within relativistic jet channels in almost all active galactic nuclei sources. The acceleration of non-thermal particles (e.g. electrons, protons) via the shock Fermi acceleration mechanism, is believed to be mainly responsible for the power-law energy distribution of the observed cosmic-rays, which in very high energies can consequently radiate high energy gamma-rays and neutrinos, through related radiation channels. Here, we will focus on the primary particle (hadronic) shock acceleration mechanism, and we will present a comparative simulation study of the properties of single and multiple relativistic shocks, which occur in AGN jets. We will show that the role of relativistic (quasi-parallel either quasi-perpendicular) shocks, is quite important since it can dramatically alter the primary CR spectral indices and acceleration eciencies. These properties being carried onto gamma-ray and neutrino radiation characteristics, makes the combination of them a quite appealing theme for relativistic plasma and shock acceleration physics, as well as observational cosmic-ray, gamma-ray and neutrino astronomy.

scholarly journals ON ACCELERATION AND PROPAGATION OF ULTRA-HIGH ENERGY COSMIC RAYS

2009 ◽  
Vol 18 (10) ◽  
pp. 1583-1586
Author(s):  
MARTIN LEMOINE
Keyword(s):  
Cosmic Rays ◽  
Active Galactic Nuclei ◽  
Large Scale ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
High Energy ◽  
Current Data ◽  
Type I ◽  
Ultra High Energy ◽  
High Energy Cosmic Rays

This paper discusses the correlation reported in 2008 by the Pierre Auger Observatory (PAO) of the arrival directions of the highest energy cosmic rays with active galactic nuclei (AGN). It is argued that these correlating AGN do not have the power required to be the sources of ultra-high energy protons. This current PAO dataset is further shown to disfavor giant radio-galaxies (both Fanaroff–Riley type I and II) as sources of ultra-high energy protons. The current data thus likely point to the local large scale structure, in which the actual sources of ultra-high energy cosmic rays camouflage. Finally, it is shown that the last gamma-ray burst in Centaurus A could explain, through rescattering on the Cen A lobes, the apparent cluster of events in this direction.

scholarly journals Prospects of testing an UHECR single source class model with the K-EUSO orbital telescope

2019 ◽  
Vol 210 ◽  
pp. 06011
Author(s):  
Oleg Kalashev ◽  
Maxim Pshirkov ◽  
Mikhail Zotov
Keyword(s):  
Cosmic Rays ◽  
Active Galactic Nuclei ◽  
Large Scale ◽  
Space Station ◽  
Galactic Nuclei ◽  
High Energy ◽  
Single Source ◽  
Class Model ◽  
High Energy Cosmic Rays ◽  
Celestial Sphere

KLYPVE-EUSO (K-EUSO) is a planned orbital detector of ultra-high energy cosmic rays (UHECRs), which is to be deployed on board the International Space Station. K-EUSO is expected to have a uniform exposure over the celestial sphere and register from 120 to 500 UHECRs at energies above 57 EeV in a 2-year mission. We employed the TransportCR and CRPropa 3 packages to estimate prospects of testing a minimal single source class model for extragalactic cosmic rays and neutrinos by Kachelrieß, Kalashev, Ostapchenko and Semikoz (2017) with K-EUSO in terms of the large-scale anisotropy. Nearby active galactic nuclei Centaurus A, M82, NGC 253, M87 and Fornax A were considered as possible sources of UHECRs. We demonstrate that an observation of more than 200 events will allow testing predictions of the model with a high confidence level providing the fraction of events arriving from any of the sources is ^10-15%, with a smaller contribution for larger samples. These numbers agree with theoretical expectations of a possible contribution of a single source in the UHECR flux. Thus, K-EUSO can provide good opportunities for verifying the minimal model basing on an analysis of the large-scale anisotropy of arrival directions of UHECRs.

scholarly journals Photon and Neutrino–Emission From Shockwaves in Active Galactic Nuclei

1989 ◽  
Vol 134 ◽  
pp. 213-214
Author(s):  
Peter L. Biermann
Keyword(s):  
Active Galactic Nuclei ◽  
Cutoff Frequency ◽  
Emission Spectra ◽  
Galactic Nuclei ◽  
High Energy ◽  
Neutrino Emission ◽  
Shock Acceleration ◽  
High Energy Cosmic Rays ◽  
Ccd Observations ◽  
Very High Energy

Many active galactic nuclei and/or associated jets and hot spots show a sharp cutoff in their nonthermal emission near ∼3 1014 Hz. Using the first order Fermi theory for particle acceleration at shocks we demonstrate that synchrotron emission and shock acceleration combine to give a maximum cutoff near to the observed frequency. We explore consequences: First, CCD-observations of the M87 jet demonstrate that the cutoff frequency decreases along the jet. Second, the detailed shape of the cutoff spectrum depends on the precise model for the turbulent wave field. Thirdly, an X-ray Synchrotron contribution from p-p and p-γ interactions exists which can match observed AGN spectra. Finally we apply the model to interpret the origin of very high energy cosmic rays, to the spectral behaviour of quasars and BL Lac's and deduce neutrino emission spectra of active galactic nuclei.

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

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 Gamma-Ray and Neutrino Signals from Accretion Disk Coronae of Active Galactic Nuclei

Galaxies ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 36
Author(s):  
Yoshiyuki Inoue ◽  
Dmitry Khangulyan ◽  
Akihiro Doi
Keyword(s):  
Active Galactic Nuclei ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
High Energy ◽  
Thermal Activity ◽  
X Ray ◽  
Cascade Models ◽  
Coronal Activity ◽  
Ngc 1068 ◽  
High Energy Particles

To explain the X-ray spectra of active galactic nuclei (AGN), non-thermal activity in AGN coronae such as pair cascade models has been extensively discussed in the past literature. Although X-ray and gamma-ray observations in the 1990s disfavored such pair cascade models, recent millimeter-wave observations of nearby Seyferts have established the existence of weak non-thermal coronal activity. In addition, the IceCube collaboration reported NGC 1068, a nearby Seyfert, as the hottest spot in their 10 yr survey. These pieces of evidence are enough to investigate the non-thermal perspective of AGN coronae in depth again. This article summarizes our current observational understanding of AGN coronae and describes how AGN coronae generate high-energy particles. We also provide ways to test the AGN corona model with radio, X-ray, MeV gamma ray, and high-energy neutrino observations.

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