Viscous Dissipation in the Galactic Center Region

Abstract

For more than two decades, X-ray observations have revealed strong iron line emission from the central few hundred parsecs of the Galaxy. We have recently suggested that, hydrogen having escaped from the Galactic potential, it might be a helium plasma. But this leaves open the problem of heating the plasma. Here we present a possible heating mechanism in which the gravitational and kinetic energy of cold molecular clouds are dissipated in the surrounding plasma by the strong viscosity acting there. The possible existence of a vertical magnetic field in this region has a strong inflience on the viscous properties and is fully taken into account. The MHD wakes of the moving clouds are analyzed in detail and it is shown that its Alfven component can be responsible for an energy dissipation strong enough to drive efficient heating.