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Astron. Astrophys. 323, 271-285 (1997)

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Acceleration mechanism in compact objects

A. Marcowith , G. Pelletier and G. Henri

Groupe d'Astrophysique de Grenoble, Université J. Fourier, BP 53X, F-38041 Grenoble Cédex, France

Received 10 April 1996 / Accepted 13 December 1996


We investigate the kinetic theory of a mixing of relativistic pair plasma in a conventional electron-proton plasma and an intense anisotropic Compton radiation field as those found in the vicinity of a compact object, a neutron star or a black hole.

In a two-flow configuration we discriminate two regimes: the first one is realized when the mass energy density of the pair plasma is lower than the ambient (electron-proton) plasma one, whereas the second one is characterized by a more massive relativistic pair plasma. The first stage, called "non relativistic regime", is entirely treated within the scheme of weak turbulence theory, and leads us to calculate the bulk Lorentz factor, the internal energy and the distribution function of the relativistic particles distribution function. We propose a new scenario to get a power law distribution. For the second stage, called the "relativistic regime", we mostly calculated an unusual instability triggered by the ambient protons that amplifies the left circularly polarized Alfvén wave of the pair plasma at synchrotron resonance. This instability plays an important role to couple the beam with the ambient plasma, and governs energy and momentum exchanges.

The kinetic theory is applied to different astrophysical sources such as Blazar and galactic "micro-Quasar" jets. We calculate the internal Lorentz factor and find it of order of [FORMULA] for extragalactic black holes, and [FORMULA] for galactic black holes. The resulting bulk Lorentz factor derived in term of the compactness of the soft photon source is of order of 10 for extragalactic sources of order of 5 for galactic sources.

Key words: acceleration of particles – instabilities – radiation mechanisms: non-thermal – turbulence – galaxies: active – galaxies:jets

Send offprint requests to: A. Marcowith

© European Southern Observatory (ESO) 1997

Online publication: June 5, 1998