A&A 419, 161-166 (2004)
DOI: 10.1051/0004-6361:20034489

In situ acceleration in the Galactic Center Arc

S. Lieb, H. Lesch and G. T. Birk

Institute for Astronomy and Astrophysics, University of Munich, Scheinerstr 1, 81679 Munich, Germany
(Received 10 October 2003 / Accepted 3 February 2004)

Abstract
For the nonthermal radio emission of the Galactic Center Arc in situ electron acceleration is imperative. The observed radio spectrum can be modeled by a transport equation for the relativistic electrons which includes particle acceleration by electric fields, momentum diffusion via scattering by magnetohydrodynamical turbulence and energy losses by synchrotron radiation. The accelerating electric fields can be regarded as a natural consequence of multiple reconnection events, caused by the interaction between a molecular cloud and the Arc region. The radio spectrum and even the recently detected 150 GHz emission, explicitely originating from the interaction regions of a molecular cloud with the magnetized Arc, can be explained in terms of quasi-monoenergetically distributed relativistic electrons with a typical energy of about 10 GeV accelerated in stochastically distributed magnetic reconnection zones.

Key words: Galaxy: center -- acceleration of particles -- radio continuum: ISM

Offprint request: S. Lieb, lieb@usm.uni-muenchen.de

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