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Session 53 - The X Clusters: Cooling Flows.
Display session, Thursday, January 08
Exhibit Hall,
We calculate the reduction of thermal conductivity \kappa and viscosity \nu in cooling flows with a tangled magnetic field. Our theory predicts an interestingly large reduction of \kappa relative to the Spitzer value for typical cooling-flow parameters. For example, for a field correlation length of 5 kpc and an electron collisional mean free path of 20 kpc, \kappa is reduced by a factor of a few hundred. We include the trapping of electrons in magnetic mirrors and the exponentially rapid divergence of neighboring field lines. Our results apply to thermal conduction over scales of perhaps 100 kpc or more, but we also discuss the collisionless reduction of the heat flux into small-scale clouds and narrow optical filaments. When l_b< \lambda, viscosity arises from a different mechanism (magnetic pumping) than in the neutral fluid case. Unlike \kappa, however, \nu is not reduced by a large factor. We provide support of our analytic results and phenomenological arguments with particle simulations.
