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Astron. Astrophys. 321, 434-443 (1997)


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Transport of relativistic nucleons in a galactic wind driven by cosmic rays

V.S. Ptuskin 1, H.J. Völk 2, V.N. Zirakashvili 1 and D. Breitschwerdt 2, 3

1 Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation (IZMIRAN), Russian Academy of Sciences, Troitsk,
142092 Moscow District, Russia
2 Max-Planck-Institut für Kernphysik, P.O.Box 103980, D-69029 Heidelberg, Germany
3 Max-Planck-Institut für Extraterrestrische Physik, P.O. Box 1603, D-85740 Garching, Germany
Dedicated to V.L. Ginzburg and J.A. Simpson at the occasion of their 80th Birthdays

Received 17 June 1996 / Accepted 21 October 1996

Abstract

For the first time an attempt is made at a self-consistent analytical description of the halo structure and the propagation of energetic particles in late type galaxies like our own. Galactic CR are produced together with hot gas by sources deep in the disk. This leads to a galactic wind and magnetohydrodynamic fluctuations (excited by the cosmic-ray streaming instability) which in turn together determine the transport of these energetic particles into intergalactic space. Wave excitation is balanced locally by nonlinear Landau damping. The cosmic-ray transport equations for the dominant nucleons are solved in an approximate form analytically. Although fully nonlinear, the resulting picture is simple and corresponds to an overall spatial structure that extends to distances considerably greater than the radius of the galactic disk. The inferred source spectrum for cosmic-ray nucleons is a rather hard power law in energy, of index [FORMULA] 2.1. The observed abundances of secondary nuclei are also consistent with this model. The observed disk-halo transition at distances [FORMULA] 1  kpc is an important part of the detailed picture in wich ion neutral friction damps short-scale magnetic fluctuations below that level.

Key words: cosmic rays – Galaxy: halo – galaxies: halos – turbulence - diffusion

Send offprint requests to: H.J. Völk

© European Southern Observatory (ESO) 1997

Online publication: June 30, 1998

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