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Astron. Astrophys. 349, 323-333 (1999)


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Diffusive shock acceleration in extragalactic jets

M. Micono 1, N. Zurlo 2, S. Massaglia 1, A. Ferrari 1 and D.B. Melrose 3

1 Dipartimento di Fisica Generale dell'Università, Via Pietro Giuria 1, I-10125 Torino, Italy
2 Dipartimento di Ingegneria Aeronautica e Spaziale, Politecnico di Torino, Corso Duca degli Abruzzi 24, I-10129 Torino, Italy
3 Research Centre for Theoretical Astrophysics, School of Physics, University of Sydney, NSW 2006, Australia

Received 17 December 1998 / Accepted 23 June 1999

Abstract

We calculate the temporal evolution of distributions of relativistic electrons subject to synchrotron and adiabatic processes and Fermi-like acceleration in shocks. The shocks result from Kelvin-Helmholtz instabilities in the jet. Shock formation and particle acceleration are treated in a self-consistent way by means of a numerical hydrocode. We show that in our model the number of relativistic particles is conserved during the evolution, with no need of further injections of supra-thermal particles after the initial one. From our calculations, we derive predictions for values and trends of quantities like the spectral index and the cutoff frequency that can be compared with observations.

Key words: acceleration of particles – hydrodynamics – instabilities – shock waves – galaxies: jets

Send offprint requests to: M. Micono

© European Southern Observatory (ESO) 1999

Online publication: August 25, 1999

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