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V. S. Ptuskin

Publications and source records attributed to V. S. Ptuskin.

At least 37 records · Page 2Linked to original sources

On ultra-high energy cosmic rays: origin in AGN jets and transport in expanding Universe

The cosmic ray source spectrum produced by AGN (Active Galactic Nucleus) jets is calculated. A distinctive feature of these calculations is the account for the jet distribution on kinetic energy. The expected cosmic ray spectrum at the Earth is determined with the use of a simple numerical code which takes into account interactions of ultra-high energy protons and nuclei with the background radiation in an expanding universe.

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Spectrum of Galactic Cosmic Rays Accelerated in Supernova Remnants

The spectra of high-energy protons and nuclei accelerated by supernova remnant shocks are calculated taking into account magnetic field amplification and Alfvenic drift both upstream and downstream of the shock for different types of supernova remnants during their evolution. The maximum energy of accelerated particles may reach $5\cdot10^{18}$ eV for Fe ions in Type IIb SNRs. The calculated energy spectrum of cosmic rays after propagation through the Galaxy is in good agreement with the spectrum measured at the Earth.

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The Tunka-133 EAS Chrenkov array - status, first results and plans

The new EAS Cherenkov array Tunka-133 with about 1 km**2 geometric acceptance area is installed in the Tunka Valley (50 km from Lake Baikal). The array willpermit a detailed study of cosmic ray energy spectrum and mass composition in the energy range of 10**15 - 10**18 eV with uniform method. The array consistsof 19 clusters, each composed of 7 optical detectors with 20 cm PMTs. Since November 2008, the first 12 clusters are in operation, commissioning of the whole array is planned for September 2009 (At the time of submission of this paperto electronic arXiv(February 2010) the completed Tunka-133 array is already taking data). We describe the array construction and DAQ, preliminary results and plans for the future development: deployment of radio-antennas and muon detectors network.

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Spectrum and composition of galactic cosmic rays accelerated in supernova remnants

The spectra of high-energy protons and nuclei accelerated by supernova remnant shocks are calculated taking into account magnetic field amplification and Alfvenic drift for different types of SNRs during their evolution. The overall energy spectrum and elemental composition of cosmic rays after propagation through the Galaxy are found.

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The Cosmic Ray Mass Composition in the Energy Range 10^15 - 10^18 eV measured with the Tunka Array: Results and Perspectives

The final analysis of the Extensive Air Shower (EAS) maximum X_max depth distribution derived from the data of Tunka-25 atmospheric Cherenkov light array in the energy range 3.10^15 - 3.10^16 eV is presented. The perspectives of X_max studies with the new Cherenkov light array Tunka-133 of 1 km^2 area, extending the measurements up to 10^18 eV, are discussed.

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Data acquisition system for the TUNKA-133 array

The new EAS Cherenkov array TUNKA-133, with about 1 km**2 sensitive area, is being installed in the Tunka Valley. The investigated energy range is 10**15-10**18 eV. It will consist of 133 optical detectors based on EMI9350 PMTs. Optical detectors are grouped into 19 clusters with 7 detectors each. The detectors are connected to the cluster box with RG-58 cables. Every PMT signal is digitized in the cluster box with 200 MHz FADC. The cluster boxes are connected to the data acquisition center with a 1 Gb/s optical link. A detailed description of the data acquisition system (DAQ) is presented.

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Modeling Bell's Non-resonant Cosmic Ray Instability

We have studied the non-resonant streaming instability of charged energetic particles moving through a background plasma, discovered by Bell (2004). 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.

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Diffusive Shock Acceleration with Magnetic Amplification by Non-resonant Streaming Instability in SNRs

We investigate the diffusive shock acceleration in the presence of the non-resonant streaming instability introduced by Bell (2004). The numerical MHD simulations of the magnetic field amplification combined with the analytical treatment of cosmic ray acceleration permit us to calculate the maximum energy of particles accelerated by high-velocity supernova shocks. The estimates for Cas A, Kepler, SN1006, and Tycho historical supernova remnants are given. We also found that the amplified magnetic field is preferentially oriented perpendicular to the shock front downstream of the fast shock. This explains the origin of the radial magnetic fields observed in young supernova remnants.

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Tunka-133 EAS Cherenkov Array: Status of 2007

The new EAS Cherenkov array Tunka-133, with about 1 km**2 sensitive area, is being installed in the Tunka Valley since the end of 2005. This array will permit a detailed study of the cosmic ray energy spectrum and the mass composition in the energy range of 10**15-10**18 eV with a unique method. The array will consist of 19 clusters, each composed of 7 optical detectors. The first cluster started operation in October 2006. We describe the data acquisition system and present preliminary results from data taken with the first cluster.

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Dissipation of Magnetohydrodynamic Waves on Energetic Particles: Impact on Interstellar Turbulence and Cosmic Ray Transport

The physical processes involved in diffusion of Galactic cosmic rays in the interstellar medium are addressed. We study the possibility that the nonlinear MHD cascade sets the power-law spectrum of turbulence which scatters charged energetic particles. We find that the dissipation of waves due to the resonant interaction with cosmic ray particles may terminate the Kraichnan-type cascade below wavelengths 10^13 cm. The effect of this wave dissipation has been incorporated in the GALPROP numerical propagation code in order to asses the impact on measurable astrophysical data. The energy-dependence of the cosmic-ray diffusion coefficient found in the resulting self-consistent model may explain the peaks in the secondary to primary nuclei ratios observed at about 1 GeV/nucleon.

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On the spectrum of high-energy cosmic rays produced by supernova remnants in the presence of strong cosmic-ray streaming instability and wave dissipation

The cosmic-ray streaming instability creates strong magnetohydrodynamic turbulence in the precursor of a SN shock. The level of turbulence determines the maximum energy of cosmic-ray particles accelerated by the diffusive shock acceleration mechanism. The present consideration continues our work Ptuskin & Zirakashvili (2003). 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 over the course of adiabatic SNR evolution (the Sedov stage) is approximately $Q(p)p^{2}\propto p^{-2}$ at energies larger than 10-30 Gev/nucleon and with the maximum particle energy that is close to the knee position in cosmic ray spectrum observed at $\sim4\times10^{15}$ eV. At earlier stage of SNR evolution - the ejecta dominated stage described by the Chevalier-Nadyozhin solution, the particles are accelerated to higher energies and have rather steep power-law distribution on momentum. 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.

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Cosmic ray production in supernova remnants including reacceleration: the secondary to primary ratio

We study the production of cosmic rays (CRs) in supernova remnants (SNRs), including the reacceleration of background galactic cosmic rays (GCRs) - thus refining the early considerations by Blandford & Ostriker (1980) and Wandel et al. (1987) - and the effects of the nuclear spallation inside the sources (the SNRs). This combines for the first time nuclear spallation inside CR sources and in the diffuse interstellar medium, as well as reacceleration, with the injection and subsequent acceleration of suprathermal particles from the postshock thermal pool. Selfconsistent CR spectra are calculated on the basis of the nonlinear kinetic model. It is shown that GCR reacceleration and CR spallation produce a measurable effect at high energies, especially in the secondary to primary (s/p) ratio, making its energy-dependence substantially flatter than predicted by the standard model. Quantitatively, the effect depends strongly upon the density of the surrounding circumstellar matter. GCR reacceleration dominates secondary CR production for a low circumstellar density. It increases the expected s/p ratio substantially and flattens its spectrum to an almost energy-independent form for energies larger than 100 GeV/n if the supernovae explode on average into a hot dilute medium with hydrogen number density $N_H=0.003$cm$^{-3}$. The contribution of CR spallation inside SNRs to the s/p ratio increases with increasing circumstellar density and becomes dominant for $N_H\gsim 1$ cm$^{-3}$, leading at high energies to a flat s/p ratio which is only by a factor of three lower than in the case of the hot medium. Measurements of the boron to carbon ratio at energies above 100 GeV/n could be used in comparison with the values predicted here as a consistency test for the supernova origin of the GCRs.

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Dissipation of Hydromagnetic Waves on Energetic Particles: Impact on Interstellar Turbulence and Cosmic Ray Transport

The diffusion of galactic cosmic rays (CR) is considered. It is anticipated that the nonlinear MHD cascade sets the power-law spectrum of turbulence from the principle scale 100 pc to much smaller scales. We found that the dissipation of waves due to the resonant interaction with energetic particles may terminate the cascade at less than 1.e13 cm. The shape of CR diffusion coefficient that was found may explain the observed peaks of secondary to primary nuclei ratios at a few GeV/n.

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Particle Acceleration in Supernova Remnants in the Presence of Streaming Instability and Nonlinear Wave Interactions

The instability in the cosmic-ray (CR) precursor of a SN shock is studied. The level of turbulence in this region determines the maximum energy of accelerated CRs. The consideration is not limited by the case of weak turbulence. It is assumed that 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. It can be as high as $10^{17}Z$ eV in young SNR and falls down to about $10^{10}Z$ eV at the end of Sedov stage ($Z$ is the particle charge). This finding may explain why the SNRs with the age more than a few thousand years are not prominent sources of very high energy $γ$-rays. The averaged spectrum of ultrarelativistic CR injected in the interstellar medium is close or somewhat steeper than $E^{-2}$.

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Limits on diffusive shock acceleration in supernova remnants in the presence of cosmic-ray streaming instability and wave dissipation

The instability in the cosmic-ray precursor of a supernova shock moving in interstellar medium is studied. The level of magnetohydrodynamic turbulence in this region determines the maximum energy of particles accelerated by the diffusive shock acceleration mechanism. The high efficiency of cosmic ray acceleration is accepted, and the consideration is not limited by the case of weak turbulence. It is assumed that 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 supernova remnant. The maximum energy can be as high as $\sim10^{17}Z$ eV in young supernova remnants and falls down to about $\sim10^{10}Z$ eV at the end of Sedov stage. Thus the standard estimate of maximum particle energy based on the Bohm limit calculated for the interstellar magnetic field strength is not justified in this case. This finding may explain why the supernova remnants with the age more than a few thousand years are not prominent sources of very high energy gamma-rays.

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Propagation model for cosmic ray species in the Galaxy

In a recent paper (Moskalenko et al., 2002), it has been shown that the flux of secondary cosmic ray (CR) antiprotons appears to be contradictory to measurements of secondary to primary nuclei ratios in cosmic rays when calculated in the same Galactic propagation model. The contradiction appears as a value of the diffusion coefficient necessary to match the secondary ratios antiproton/proton and B/C. In particlular, it was shown that the reacceleration models designed to match secondary to primary nuclei ratios produce too few antiprotons. It is, however, clear that some reacceleration is unavoidable in the turbulent interstellar medium. Here we discuss an idea of how to improve reacceleration model by allowing for the damping of interstellar turbulences on the small scale by cosmic rays, mostly protons. This would lead to increase in the mean free path lenghts at low energies, the well-known phenomena empirically discovered in the Leaky Box models, thus producing less secondary nuclei. Antiprotons will remain almost non-affected due to their high energy threshold of production cross section.

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