  In addition to lines originating in a soft phase at ~0.8 keV and to cold
molecular clouds, the X-ray spectra from the Galactic center region also
exhibit properties similar to those of a diffuse, thin, very hot plasma at 8
keV on a scale of hundreds of parsecs. This phase is surprising for more than
one reason. First, such a hot plasma should not be bound to the Galactic plane
and the power needed to sustain the escaping matter would be higher then any
known source. Second, there is no known mechanism able to heat the plasma to
more than a few keV. Recently we have suggested that, hydrogen having escaped,
the hot plasma could be a helium plasma, heavy enough to be gravitationally
confined. In this case, the required power is much more reasonable. We present
here a possible heating mechanism which taps the gravitational energy of the
molecular clouds. We note that the 8 keV plasma is highly viscous and we show
how viscous friction of molecular clouds flowing within the hot phase can
dissipate energy in the gas and heat it. We detail the MHD wake of a spherical
cloud by considering the different MHD waves the cloud can excite. We find that
most of the energy is dissipated by the damping of Alfvenic perturbations in
two possible manners, namely by non-linear effects and by a large scale
curvature of the field lines. Depending on the field strength, this heating can
balance the radiative cooling. We note that the plasma parameters may be
optimal to make the dissipation most efficient, suggesting a self-regulation
mechanism. The loss of kinetic and gravitational energy also causes accretion
of the clouds and may have significant action on the gas dynamics in this
region between the large scale, bar dominated flow and the central accretion to
the massive black hole.
