宇宙射線電漿流體力學的一項理論研究(2/3)

Roughly speaking there is an equipartition of energy among different phases of gas, magnetic field and cosmic rays in the interstellar medium of our Galaxy. They should all contribute to the structure and evolution of the interstellar medium. In this proposal, the dynamical interactions between them will be studied theoretically. We focus on two related topics: (1) cosmic-ray modified outflows, and (2) hydrodynamics with cosmic-ray viscosity.Magnetic field and its fluctuations or waves act as a clutch between cosmic rays and thermal plasma. We have developed multi-fluid models to study their interactions. In these models, cosmic rays and hydromagnetic waves are treated as massless fluids with significant energy density. We are interested in astrophysical outflows from a gravitational potential well, e.g., galactic wind. To learn some basic structures of the flows, we adopt the idealised flux-tube formulation. The main effort will be on different classes of outflows in divergent flux-tube geometry, in particular, possible transonic solutions.Flux-tube formulation has limitations and we think about improvement. We will try extending it to equatorial winds first, and perhaps, to flux-surface formulation later.Recently, there is a revived interest in cosmic-ray viscosity, a long forgotten cosmic ray acceleration mechanism in large scale shear flows. We would like to develop a two-fluid model to study the dynamics of a system including this mechanism. As the transport equation is very different from the traditional one, we have to derive a brand new cosmic ray energy equation, and also some necessary alterations to the momentum and energy equations of the plasma. When the model is ready, we will analyse some simple examples to understand basic properties of the system. We shall develop a simulation code for the system. When everything is ready, simulating the Fermi bubbles will be our first goal.