Particle acceleration in rotating and shearing jets from AGN

¹ Institut für Theoretische Physik und Astrophysik der Universität Würzburg, Am Hubland, 97074 Würzburg, Germany e-mail: mannheim@astro.uni-wuerzburg.de
² Universitäts-Sternwarte Göttingen, Geismarlandstr. 11, 37083 Göttingen, Germany e-mail: frieger@uni-sw.gwdg.de

Corresponding author: F. Rieger, frieger@uni-sw.gwdg.de

Received: 18 March 2002
Accepted: 26 September 2002

Abstract

We model the acceleration of energetic particles due to shear and centrifugal effects in rotating astrophysical jets. The appropriate equation describing the diffusive transport of energetic particles in a collisionless, rotating background flow is derived and analytical steady state solutions are discussed. In particular, by considering velocity profiles from rigid, over flat to Keplerian rotation, the effects of centrifugal and shear acceleration of particles scattered by magnetic inhomogeneities are distinguished. In the case where shear acceleration dominates, it is confirmed that power law particle momentum solutions exist, if the mean scattering time is an increasing function of momentum. We show that for a more complex interplay between shear and centrifugal acceleration, the recovered power law momentum spectra might be significantly steeper but flatten with increasing azimuthal velocity due to the increasing centrifugal effects. The possible relevance of shear and centrifugal acceleration for the observed extended emission in AGN is demonstrated for the case of the jet in the quasar 3C273.