Title: 3D MHD Numerical Study of CMEs Initiation, Propagation and  Interaction From Near the Sun to the Earth

Speaker: Prof. Fang Shen (State Key Laboratory of Space Weather, National Space Science Center (NSSC), CAS)

Location: 3rd floor, middle conference room

Time: 9:30am, September 26.

Abstract:

Corona mass ejections (CMEs) and their interplanetary consequences (ICMEs)  represent different aspects of the same phenomenon responsible for large non-recurrent geomagnetic storms. Because of their great complexity, each aspect has typically been investigated separately, which is useful for revealing the basic underlying physics. However, in order to obtain a complete picture, one needs to conduct three-dimensional (3D) magnetohydrodynamic (MHD) modelling to consider the coupling between the corona and the interplanetary processes. In this talk, firstly, a few popular CME initiation models will be reviewed in the introduction part. Secondly, a 3D time-dependent, numerical MHD model with asynchronous and parallel time-marching method will be presented to investigate the propagation of CMEs in the nonhomogenous background solar wind flow. The background solar wind is constructed based on the self-consistent source surface with observed line-of-sight of magnetic field and density from the source surface of 2.5 Rs to the Earth’s orbit (215 Rs) and beyond. Thirdly, we choose the well-defined halo-CME event of 4-6 April 2000 and the two successive CMEs occurring on 2001 March 28 as our test cases. In our study, the CMEs are simulated by means of a simple flux rope model: a high-density, -velocity and -temperature magnetized plasma blob is superimposed on a steady state background solar wind with an initial launch direction. The dynamical propagation and interaction of a CME/two CMEs with the background solar wind flow between 2.5 and 220 Rs is investigated. Especially, for the single CME event, the evolution of the physical parameters at the cobpoint, which is located at the shock front region magnetically connected to ACE spacecraft, is investigated. And for the two CMEs event, the forces which cause the acceleration and deceleration of CMEs propagation are also studied. Finally, in this validation study we find that this 3D MHD model, with the asynchronous and parallel time-marching method and the simple flux rope as CME model, provide a relatively satisfactory comparison with the ACE spacecraft observations at the L1 point.