Anomalous Magnetic Viscosity And Its Application In Accretion Disks

Accretion disk theory has been used to examin the formation and evolution of the solar nebula in1920s. And Lynden-Bell, in1969, firstly explained the energy mechanism of the quasars based on this thoery, which leads the application of the accretion disk theory to get breakthrough progress. In physics, the necessary process, by which the gas losses its angular momentum to accrete onto the massive central object, must be undergone during the formation of a disk. The structure and evolution of an accretion disk is essentially determined by the transfer efficiency of angular momentum. While the angular momentum transfer is dependent on the nature and magnitude of the viscosity. The investigation results shown that molecular viscosity is totally inadequate and some kind of turbulent viscosity is required. The concept of turbulent viscosity was introduced by Shakura&Sunyaev in1973, and the α-viscosity prescription established, which has been applied widely. It is noteworthy that, despite the successes, the a ansatz is lack of detailed knowledge about the underlying physics of viscosity and retains no information about the mechanism generating the turbulence.Fortunately, an exciting work by Li and Zhang has shown that the magnetic fields self-generated by the transverse plasmons are modulationally unstable, leading to a self-similar collapse of the magnetic filed and resulting in strong local magnetic structures; highly spatially intermittent flux is responsible for generating the anomalous viscosity. The structures and evolution of thin disks surrounding a young stellar object and protostar have been investigated in the frame of anomalous magnetic viscosity prescription, respectively, in this paper. The results show the distribution of effective temperature is agreement with the observation.The second content is to generalize the previous work by Li and Zhang to the case that the relativistic effects of electrons are considered. Based on the nonlinear coupling equations which can describe the temporal evolution of the envolope of electric field, ion acoustic motion and self-generated magnetic field, the self-similar solution for collapse is found and the kinematic anomalous magnetic visosity coefficient in a relativistic accretion disk is obtained. The result indicates that the anomalous magnetic visosity in a relativistic accretion disk has very different dependence on the effective temperature of electrons from the non-relativistic one.And the third part we have examined is based on the the governing equations for the evolution of self-generated gravitoelectomagnetism(GEM) field established by Li Xiaoqing et al. It has been proved that the GEM field is modulational unstable, the perturbed GM field will collapse into a small local region. The interactions between highly spatially intermittent gravitomagnetic flux and the macrofluid are responsible for the anomalous gravitomagnetic viscosity. In the present paper, the anomalous gravitomagnetic viscosity coefficient is obtained. The results indicate that, gravitomagnetic viscosity would result in a factor of nearly eignt orders amplification to molecular viscosity, which maybe helpful for understanding the relevant properties and phenomena in the self-gravitating accretion disks.