On the Momentum Diffusion of Radiating Ultrarelativistic Electrons in a Turbulent Magnetic Field

By Ł. Stawarz, V. Petrosian. 2008

145 citations recorded by the source corpus.

Here we investigate some aspects of stochastic acceleration of ultrarelativistic electrons by magnetic turbulence. In particular, we discuss the steady state energy spectra of particles undergoing momentum diffusion due to resonant interactions with turbulent MHD modes, taking rigorously into account direct energy losses connected with different radiative cooling processes. For the magnetic turbulence we assume a given power spectrum of the type W(k) ∝ k−q. In contrast to the previous approaches, however, we assume a finite range of turbulent wavevectors k, consider a variety of turbulence spectral indices 1 ⩽ q⩽ 2, and concentrate on the case of a very inefficient particle escape from the acceleration site. We find that for different cooling and injection conditions, stochastic acceleration processes tend to establish a modified ultrarelativistic Maxwellian distribution of radiating particles, with the high-energy exponential cutoff shaped by the interplay between cooling and acceleration rates. For example, if the timescale for the dominant radiative process scales with the electron momentum as ∝pr, the resulting electron energy distribution is of the form ne(p) ∝ p2exp [ − (1/a)(p/peq)a] , where a = 2 − q − r and peq is the equilibrium momentum defined by the balance between the stochastic acceleration and energy loss timescales. We also discuss in more detail the synchrotron and inverse-Compton emission spectra produced by such an electron energy distribution, taking into account Klein-Nishina effects. We point out that the curvature of the high-frequency segments of these spectra, even though they are produced by the same population of electrons, may be substantially different between the synchrotron and inverse-Compton components.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/96da2a5172b0802775380f2e9378f38bb8f45372

How researchers see this paper

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In Astronomy and Astrophysics

1. F. Tavecchio
2. Y. Kovalev
3. E. Orlando
4. C. Dermer
5. M. Lister
6. A. Pushkarev
7. L. Maraschi
8. H. Krawczynski

In Nuclear and High Energy Physics

1. F. Tavecchio
2. C. Dermer
3. E. Orlando
4. Y. Kovalev
5. M. Lister
6. L. Maraschi
7. A. Pushkarev
8. H. Krawczynski

Citations in the corpus

• STOCHASTIC ACCELERATION AND THE EVOLUTION OF SPECTRAL DISTRIBUTIONS IN SYNCHRO-SELF-COMPTON SOURCES: A SELF-CONSISTENT MODELING OF BLAZARS’ FLARES (2011, unknown): “Using a power-law form for the acceleration terms, and in the case of only synchrotron losses (or any cooling process that can be expressed as a power-law function of γ), it is possible to give an analytic expression of f(q, γ̇) (Katarzyński et al. 2006; Stawarz & Petrosian 2008).”
• INSIGHTS INTO THE HIGH-ENERGY γ-RAY EMISSION OF MARKARIAN 501 FROM EXTENSIVE MULTIFREQUENCY OBSERVATIONS IN THE FERMI ERA (2011, background): “However, some smoothly curved spectral shape might perhaps be an alternative representation of the electron spectrum (e.g., Stawarz & Petrosian 2008; Tramacere et al. 2009).”