Three-dimensional MHD Simulations Of CMEs

Coronal mass ejection（CME）is a large burst of plasma from the sun in a very short time,which is one of the most frequently eruptive phenomena in the solar atmosphere.It is the mainly drive force for space disturbance,which can cause significant change in the geospace environment.Hence,CME is the major research contents of space weather research in the solar-interplanetary evolutionary process.Numerical simulations based on magnetohydrodynamics（MHD）can depict plasma self-consistently with applications in the globally capturing of coronal dynamical evolution,which has been the valid tool in the investigation of the response of coronal to the burst of CME and coronal planetary evolutionary process of CME.The AMR-SIP-MHD model developed in our Lab was employed in this simulation.Six low-latitude spherical meshes to envelope a spherical surface with partial overlap on their boundaries（six-component grid system）is used in this model,which can not only overcome the convergent and singular problems,but also be convenient for the parallel programming.With the CESE format,time and space was equally treated in the model,which is different from the other difference schemes used in traditional solar wind model.GLM and eight-wave methods were combined together to control the divergence of magnetic field.The simulated area from near-sun（1 Rs）to near-earth orbit.With the parallel AMR package PARAMESH,we can refine the grid in the initial trigger point of CME as well as the position of CME in its propagation process to fulfill the grid size in the calculation of fine structure.The 24^th Solar cycle began in December 2008,and the number of sunspots reached the peak in 2014.The number of sunspots in this cycle is less than the two previous cycle.We selected four typical Carrington Rotations for simulation:2055（solar minimum）,2104（rising phase）,2152（solar maximum）,2183（decling phase）.At present,in most of the simulated CME,the burst process and planetary propagationprocesswasseparatelysimulated,whichwerealways slow-velocity-CME.In this work,we tried to simulate the fast-velocity-CME which was burst on December 13^rd,2006.Based on the potential field model and observed solar photosphere magnetic fields,time relaxation method was employed to get the steady solutions of the background solar wind.With the obtained steady solution,high-density,high-speed and high-temperature fluxrope was added near the solar orbit to quantitatively simulate the evolutionary propagation process of CME from near-coronal to near-earth orbit.In consideration of space size and calculation time,a emerging fluxrope was added in the surface of solar with the steady solution of background solar wind in the coronal region（1 Rs to 35 Rs）to qualitatively simulate the evolutionary propagation process of CME from burst to coronal region.It qualitatively verified the valid of the AMR-SIP-MHD model in the continuous simulation of CME from its burst to the coronal planetary evolutionary process.The effects of heat conduction term on the parameters of solar wind was also compared in the simulation of background solar wind,which was found that its effects on solar wind near-sun orbit was correlated with open and closed of magnetic field lines.