Numerical Research About Coronal Mass Ejections

The ideal Magnetohydrodynamic equations(MHD), the governing equations of the solar atmosphere dynamical process, are taken to numerically simulate Coronal Mass Ejection(CME) phenomena. At first, we develop suitable numerical algorithms corresponding to the features of different forms of MHD equations. We generalize Non-oscillatory, Non-free parameter Discrete scheme(NND) for the first time and apply it to the conservative form of MHD equations. The work lies in two main aspects: 1) To effectively reduce the error of Lorentz force caused by the non-zero numerical value of magnetic field divergence, we divided magnetic field into two parts, one is potential field invariant of time and the other is non-potential field varying with time and get an improved conservative form of MHD equations. 2) Considering MHD equation features, we put forward a flux splitting method applicable for the conservative form of MHD equations. With the method we can apply NND scheme to MHD equation effectively. About non-conservative form of MHD equations, we apply second order accuracy MacCormackII scheme to three dimensional MHD equations and apply non-reflective projected characteristic boundary condition to inner boundary for the first time in this three-dimensional case, which effectively stabilize computation. With the numerical model, we get a stable and self-consistent background solar wind of Carrington rotation 1935 at May 1998. This makes a foundation for simulating CME events.Second, in order to eliminate geometry singularity related to usual two-dimensional MHD governing equations in solar meridian plane at solar poles, weintroduce a new two-dimensional MHD model. With the model, we succeed in simulating LACO-C2 image observed at May 2 1998.Finally, we simulate CME propagation features in corona numerically. Background structure for CME propagation is obtained by the time relaxation method, which guarantees it stable and self-consistent. CME triggering model has concentric circular magnetic field profiles to make CME magnetic field structure similar to that in the section of the magnetic cloud structure. Numerical results present propagation features in meridian plane of CME events triggered at different places of solar surface and numerically testify the effect of propagating CME deflecting to current sheet. When numerically simulating CME events between two streamers, we construct a potential magnetic field by properly combining a dipole and a hexadpole and calculate a stable and self-consistent background after a long time interaction between the potential magnetic field and solar wind flow. Agreeing with observation, the polarity at two solar-magnetic poles are opposite in the background of the stable and self-consistent solution. With this background, we trigger CME with the triggering model between two streamers to make research about propagation features of CMEs. Numerical results tell us that CMEs are confined by two streamers to propagate between them. CME magnetic field profiles are similar to those in the section of magnetic cloud, which can explain partial features of magnetic cloud observed at 1AU. Near CMEs, there exist areas that pressure and Lorentz force play a central role, which can help for analysis of CME observational data at 1AU...