It is shown that the acceleration of particles by a powerful relativistic jet associated with the activity of a supermassive black hole in the Galactic center several million years ago may explain ...the observed cosmic ray spectrum at energies higher than \(10^{15}\) eV. The accelerated particles are efficiently confined in the extended magnetized gas halo created by the supernova and central black hole activity just after the Galaxy formation. We found that both the heavy and light chemical composition of ultra-high energy cosmic rays can be consistent with observations.
The propagation of ultrahigh energy nuclei in an expanding universe filled with background electromagnetic radiation is considered. A numerical method for solving the inverse problem for the equation ...of cosmic ray transport is developed. The method allows us to determine a source spectrum from the cosmic ray spectrum observed near Earth. The spectra of injected protons and nuclei of iron were found in extragalactic sources under the assumption that these types of particles predominate in the composition of the sources. The method of calculation is illustrated using observational data obtained in the Auger and Telescope Array experiments.
The instability in the cosmic-ray precursor of a supernova shock is studied. The level of turbulence in this region determines the maximum energy of accelerated particles. The consideration is not ...limited by the case of weak turbulence. It is assumed that the Kolmogorov type nonlinear wave interactions together with the ion-neutral collisions restrict the amplitude of random magnetic field. As a result, the maximum energy of accelerated particles strongly depends on the age of a SNR. The average spectrum of cosmic rays injected in the interstellar medium in the course of adiabatic SNR evolution takes the approximate form
E
−2 at energies larger than 10–30
GeV/nucleon with the maximum energy that is close to the position of the knee in cosmic-ray spectrum at 4
×
10
15
eV. At an earlier stage of SNR evolution – the ejecta-dominated stage, the particles are accelerated to higher energies and have a rather steep power-law distribution. These results suggest that the knee may mark the transition from the ejecta-dominated to the adiabatic evolution of SNR shocks which accelerate cosmic rays.
Context.Recent observations of hard X-rays and very high energy gamma-rays from a number of young shell type supernova remnants indicate the importance of detailed quantitative studies of energy ...spectra of relativistic electrons formed via diffusive shock acceleration accompanied by intense nonthermal emission through synchrotron radiation and inverse Compton scattering. Aims.The aim of this work was derivation of exact asymptotic solutions of the kinetic equation which describes the energy distribution of shock-accelerated electrons for an arbitrary energy-dependence of the diffusion coefficient. Methods.The asymptotic solutions at low and very high energy domains coupled with numerical calculations in the intermediate energy range allow analytical presentations of energy spectra of electrons for the entire energy region. Results.Under the assumption that the energy losses of electrons are dominated by synchrotron cooling, we derived the exact asymptotic spectra of electrons without any restriction on the diffusion coefficient. We also obtained simple analytical approximations which describe, with accuracy better than ten percent, the energy spectra of nonthermal emission of shock-accelerated electrons due to the synchrotron radiation and inverse Compton scattering. Conclusions.The results can be applied for interpretation of X-ray and gamma-ray observations of shell type supernova remnants, as well as other nonthermal high energy source populations like microquasars and large scale synchrotron jets of active galactic nuclei.
Reacceleration of cosmic rays produced by galactic sources on the galactic wind termination shock is considered. The problem of the cosmic ray spectrum continuity is investigated. Numeric results are ...presented and discussed. We found that a smooth spectral transition from the galactic cosmic rays to the cosmic rays reaccelerated at the galactic wind termination shock is difficult to produce, if the maximum energy of accelerated particles is the same throughout the surface of the termination shock. The possible solution of this problem is the non-spherical termination shock with different maximum energies at different places of the shock.
It is shown that the relativistic jets associated with the growth and past activity of the supermassive black hole in the Andromeda galaxy could be the main source of cosmic rays with energies above ...\(10^{15}\) eV. Most of the cosmic ray energy is related to a bow shock of the jet that produces multi-PeV cosmic rays with light composition. The highest energy cosmic rays with heavy composition are produced in the jet itself. The spectra of energetic particles produced in Andromeda galaxy and propagated to the Earth are calculated and compared with observations.
We consider diffusive shock acceleration in supernova remnants throughout their evolution including a radiative stage. It is found that a more efficient acceleration and fast exit of particles at the ...radiative stage results in the hardening of the source cosmic ray proton and electron spectra at energies \(\sim 100-500\) GeV. The effect is stronger for cosmic ray electrons.
The spectra of protons, nuclei, and electrons accelerated by shocks in supernova remnants of different types were determined. The calculations were made using a numerical code that allows us to model ...spherical shock evolution and particle acceleration with allowance for the back reaction of accelerating particles on a hydrodynamic flow. The effect of Alfvenic particle drift in the amplified magnetic field in the regions upstream and downstream of the shock was taken into consideration. The maximum energy of accelerated particles is as high as ∼5 × 10
18
eV for iron nuclei in Type IIb supernova remnants. The calculated spectrum and composition of cosmic rays in the interstellar medium are in good agreement with observations.
We present physical motivations and advantages of the new gamma-observatory TAIGA (Tunka Advanced Instrument for cosmic ray physics and gamma-ray astronomy). TAIGA will be located in the Tunka ...valley, 50km to the west of Lake Baikal, at the same place as the integrating air Cherenkov detector for cosmic rays Tunka-133. The TAIGA array is a complex, hybrid detector for ground-based gamma-ray astronomy for energies from a few TeV to several PeV as well as for cosmic ray studies from 100TeV to several EeV. The array will consist of a wide angle Cherenkov array – TAIGA-HiSCORE with 5km2 area, a net of 16 IACT telescopes (with FOV of about 9.72°×9.72°) as well as muon and other detectors. We present the current status of the array construction.
PDF
