We investigate acceleration of cosmic rays by shocks and accretion flows in galaxy clusters. Numerical results for spectra of accelerated particles and nonthermal emission are presented. It is shown ...that the acceleration of protons and nuclei in the nearby galaxy cluster Virgo can explain the observed spectra of ultra high energy cosmic rays.
Cosmic ray acceleration by astrophysical shocks in supernova remnants is briefly reviewed. Results of numerical modeling taking into account magnetic field amplification by streaming instability and ...shock modification are presented. Nonthermal emission produced by accelerated particles in young and old supernova remnants is compared with available data of radio, X-ray, and gamma-ray astronomy. We also discuss a possibility of particle acceleration to PeV energies at supernova shocks propagating in the interstellar bubbles created by stellar winds of supernova progenitors.
The processes responsible for the broadband radiation of the young supernova remnant Cas A are explored by using a new code that is designed for a detailed treatment of the diffusive shock ...acceleration of particles in the nonlinear regime. The model is based on spherically symmetric hydrodynamic equations complemented with transport equations for relativistic particles. Electrons, protons, and the oxygen ions accelerated by forward and reverse shocks are included in the numerical calculations.We show that the available multi-wavelength observations in the radio, X-ray, and gamma-ray bands can be best explained by invoking particle acceleration by both forward and reversed shocks. Although the TeV gamma-ray observations can be interpreted by interactions of both accelerated electrons and protons/ions, the measurements by Fermi Large Area Telescope at energies below 1 GeV give a tentative preference to the hadronic origin of gamma-rays. Then, the acceleration efficiency in this source, despite the previous claims, should be very high; 25% of the explosion energy (or approximately 3 x 10 super(50) erg) should already be converted to cosmic rays, mainly by the forward shock. At the same time, the model calculations do not provide extension of the maximum energy of accelerated protons beyond 100 TeV. In this model, the acceleration of electrons is dominated by the reverse shock; the required 10 super(48) erg can be achieved under the assumption that the injection of electrons (positrons) is supported by the radioactive decay of super(44)Ti.
We have studied the nonresonant streaming instability of charged energetic particles moving through a background plasma, discovered by Bell. We confirm his numerical results regarding a significant ...magnetic field amplification in the system. A detailed physical picture of the instability development and of the magnetic field evolution is given.
The propagation of ultrahigh-energy cosmic rays from nearby sources is studied. It is shown that the spectrum, chemical composition, and anisotropy observed at energies above 5 × 10
18
eV can be ...explained within the model of one nearby galaxy (M87) if the source is strongly enriched with heavy nuclei.
A study is performed of the acceleration of cosmic rays by shock waves propagating in bubbles of hot rarefied gas created by the stellar wind of supernova progenitors. Spectra of accelerated ...particles produced in type Ib/c supernova remnants are determined.
A nonlinear model of cosmic-ray acceleration at the shock fronts in the supernova remnants W28, W44, and IC433 is investigated. The hydrodynamic evolution of a supernova remnant, including the shock ...modification by the pressure of accelerated particles and the streaming instability of particles upstream of the shock propagating in a partially ionized interstellar gas, is modeled. The electromagnetic radiation generated by accelerated particles is calculated and compared with observations in a wide range of photon energies.
The transport equation for cosmic rays in the Galaxy is solved simultaneously with equation for energy density of magnetohydrodynamic turbulence. The obtained spectra of cosmic ray nuclei with ...energies 10
5
to 10
11
eV are consistent with observational data, including the peak in the ratio of secondary to primary nuclei fluxes at around 1 GeV/nucleon.
Non-linear diffusion of cosmic rays Ptuskin, V.S.; Zirakashvili, V.N.; Plesser, A.A.
Advances in space research,
08/2008, Letnik:
42, Številka:
3
Journal Article
Recenzirano
The propagation of cosmic rays in the interstellar medium after their release from the sources – supernova remnants – can be attended by the development of streaming instability. The instability ...creates MHD turbulence that changes the conditions of particle transport and leads to a non-linear diffusion of cosmic rays. We present a self-similar solution of the equation of non-linear diffusion for particles ejected from a SNR and discuss how obtained results may change the physical picture of cosmic ray propagation in the Galaxy.
A study is performed of the effect the cosmological evolution and spatial distribution of sources have on solving the inverse problem of determining the spectra of ultrahigh energy cosmic ray ...sources. The solution allows for the propagation and energy losses of protons and nuclei in the expanding Universe. It is established that active galactic nuclei are the most probable sources of ultrahigh energy cosmic rays.
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