物理系seminar：Transport and Accretion Processes in Protoplanetary Disks: A New Paradigm

报告题目： Transport and Accretion Processes in Protoplanetary Disks: A New Paradigm 报告人：白雪宁 (CfA, Harvard) 报告时间： 2013年7月4日13点30分报告地点：理科楼B315 摘要： The structure and evolution of protoplanetary disks (PPDs) are key to understanding many aspects of planet formation. Due to extremely weak level of ionization, the gas dynamics of PPDs is largely controlled by non-ideal magnetohydrodynamical effects, including Ohmic resistivity, Hall effect and ambipolar diffusion (AD). Most previous studies considered only the effect of Ohmic resistivity under the framework of magnetorotational instability (MRI) driven accretion with dead zones. We show via self-consistent local numerical simulations that the inclusion of ambipolar diffusion (AD) qualitatively changes the conventional picture. In the inner disk around 1 AU, the MRI is suppressed due to the inclusion of AD, and the disk becomes completely laminar. Instead, a strong magnetocentrifugal wind can be launched in the presence of a weak vertical field threading the disk that efficiently drives disk accretion. With a parameter survey, we find that wind-dominated accretion with laminar disk is likely to extend to about 5-10 AU. Beyond this radius, angular momentum transport is likely to proceed through a combination of wind and the MRI, and eventually completely dominated by the MRI in the outer disk. Our simulation results provide key ingredients for a new paradigm on the transport and accretion processes in PPDs.