The Role of Plasma Instabilities in the Propagation of Gamma-rays from Distant Blazars PDF Download

Author: A. Saveliev
Publisher:
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Category :
Languages : en
Pages : 0

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Author: Iman Rafighi
Publisher:
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Category :
Languages : en
Pages : 0

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Modern gamma-ray telescopes, provide the main stream of data for astrophysicists in quest of detecting the sources of gamma rays such as active galactic nuclei (AGN). Many blazars have been detected with gamma-ray telescopes such as HESS, VERITAS, MAGIC and Fermi satellite as sources of gamma-rays with the energy E ≥ 100 GeV. These very-high-energy photons interact with extragalactic background light (EBL) producing ultra-relativistic electron-positron pairs. Observations with Fermi-LAT indicate that the GeV gamma-ray flux from some blazars is lower than that predicted from the full electromagnetic cascade. The pairs can induce electrostatic and electromagnetic instabilities. In this case, wave-particle interactions can reduce the energy of the pairs. Therefore, the collective plasma effects can also substantially suppress the GeV-band gamma-ray emission affecting as well the IGMF constraints. Using Particle in cell (PIC) simulations, we have revisited the issue of plasma instabilities induced by electron-positron beams in the fully...

Author: Mahmoud Alawashra
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Languages : en
Pages : 0

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Relativistic pair beams produced in the cosmic voids by TeV gamma rays from blazars are expected to produce a detectable GeV-scale cascade emission missing in the observations. The suppression of this secondary cascade implies either the deflection of the pair beam by intergalactic magnetic fields (IGMFs) or an energy loss of the beam due to the electrostatic beam-plasma instability. IGMF of femto-Gauss strength is sufficient to significantly deflect the pair beams reducing the flux of secondary cascade below the observational limits. A similar flux reduction may result in the absence of the IGMF from the beam energy loss by the instability before the inverse Compton cooling. This dissertation consists of two studies about the instability role in the evolution of blazar-induced beams. Firstly, we investigated the effect of sub-fG level IGMF on the beam energy loss by the instability. Considering IGMF with correlation lengths smaller than a few kpc, we found that such fields increase the transverse momentum of the pair beam particles, ...

Author: Donat G. Wentzel
Publisher: CRC Press
ISBN: 9780677135205
Category : Science
Languages : en
Pages : 440

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Author: Mohamad Shalaby
Publisher:
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Category : Active galactic nuclei
Languages : en
Pages : 145

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Blazars are the main source of extragalactic very high energy gamma-rays. These gamma rays annihilate on the extragalactic background light, producing electron-positron pair beams with TeV energies. The pair beams are very dilute, with beam-IGM density ratio of $\alpha \sim 10^{-15}$, ultra-relativistic, $\gamma \sim 10^6$, and energetically subdominant ($\gamma \alpha \sim 10^{-9}$). Such pair beams suffer from prevailing cosmological scale, linear beam-plasma instabilities. The associated instability growth rates suggest that at least initially these overwhelmingly dominate inverse Compton cooling, currently the only alternative mechanism by which the pair beams lose energy. Therefore, the full non-linear evolution of the instabilities is key to determining the mechanism by which these pair-beams lose their energy. Kinetic numerical simulations are the only method by which we can currently study the full non-linear evolution of the blazar-induced beam-plasma instabilities. However, the extreme parameters of the pair beams make direct simulations via existing particle-in-cell (PIC) codes infeasible. To address this, we developed a new Spatially Higher-order Accurate, Relativistic PIC algorithm (SHARP). A one dimensional implementation of the SHARP algorithm (SHARP-1D) is given in detail. We show explicitly that SHARP-1D can overcome a number of the limitations of existing PIC algorithms. Using SHARP-1D, we demonstrate a number of points that are important to correctly simulate the full evolution of beam-plasma instabilities. We show that convergence for PIC algorithms requires increasing both spatial resolution and the number of particles per cell concurrently. For a beam-plasma system, we show that the spectral resolution is another important resolution criteria and under-resolved simulations can lead to erroneous physical conclusions. We quantify the required box sizes to faithfully resolve the spectral support of the instabilities. When the background plasmas contain structure, we show that a significant fraction of beam energy (similar to that in uniform plasma simulations; $\sim 20$\%) is, still, lost during the linear evolution of the electrostatic unstable modes. Compared to uniform plasma growth rates, we find lower growth rates, however, the non-uniform systems stay longer in the linear regime. Therefore, the IGM inhomogeneities are unlikely to affect the efficiency of beam-plasma instabilities to cool the blazar-induced pair beams.

Author: P.J. Palmadesso
Publisher: Springer Science & Business Media
ISBN: 9400995008
Category : Science
Languages : en
Pages : 307

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Proceedings of a Symposium organized within the XIXth URSI General Assembly held in Helsinki, Finland, July 31-August 8, 1978

Author: A. Hasegawa
Publisher: Springer Science & Business Media
ISBN: 3642659802
Category : Science
Languages : en
Pages : 229

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In recent years the significant progress in satellite-based observations of plasma states and associated electromagnetic phenomena in space has resulted in the accumulation of much evidence of various plasma instabilities. Today plasma instabilities are believed to be responsible for electromagnetic radiation as well as for many of the macroscopic dynamics of plasmas in space. Most students who begin to study plasma physics are intrigued by the unstable nature of plasmas compared with other states of matter; however, they often become frustrated because there are so many in stabilities. Such frustration explains in part why there is no textbook which treats this subject exclusively. A description of plasma instabilities in a systematic way is nontrivial and takes a pertinacious effort. This book is an attempt to provide a basic introduction on the subject and covers most of the important instabilities. However, the author must apologize for any omission of references to contributions of individuals who deserve more credit. The reader is assumed to have a general knowledge of plasma physics obtainable in an undergraduate course. The book is intended to be used as a reference text on the subject of plasma instabilities at the under graduate level as well as for a text in a special course in graduate school. Because the book is part of a series on physics and chemistry in space, emphasis is placed on plasma instabilities relevant in space plasmas.

Author: W. Bernstein
Publisher:
ISBN:
Category : Gamma rays
Languages : en
Pages : 24

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Author: Lev Dorman
Publisher: Springer Science & Business Media
ISBN: 1402051018
Category : Science
Languages : en
Pages : 877

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Chapter 1 briefly describes the main properties of space plasmas and primary CR. Chapter 2 considers the problem of CR propagation in space plasmas described by the kinetic equation and different types of diffusion approximations. Chapter 3 is devoted to CR non-linear effects in space plasmas caused by CR pressure and CR kinetic stream instabilities with the generation of Alfvèn turbulence. In Chapter 4 different processes of CR acceleration in space plasmas are considered. The book ends with a list providing more than 1,300 full references, a discussion on future developments and unsolved problems, as well as Object and Author indexes.

Author: Ferdinand Cap
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 508

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