较小尺度磁螺旋线管相互作用的数值研究

在子午面内,偶极子场和六极子场适当叠加得到势磁场,势磁场与太阳风长时间相瓦作用得到特殊的冕流背景结构.在这种背景结构下,两个较小尺度的磁螺旋线管模型能够连续浮入到计算域,在计算域内相互作用,触发了日冕物质抛射(CME).在数值模拟这一过程时,较小尺度的磁螺旋线管模型具有同心圆形磁场结构,模型中心等离子压强与边界压强之比m=2,模型的半径分别取为a=0.07 R.和a=0.1 Rs(Rs为太阳半径).在这两种情况下,得到了两种典型的计算结果.当a=0.07 Rs时,两个磁螺旋线管模型相瓦作用,在7 Rs内融合成一个磁螺旋线管模型,向外传播;当a=0.1 Rs时,两个磁螺旋线管模型相互作用,作为一个整体向外传播,在计算域内没有融合到一起,基本上保持各自的磁场结构. 

Numerical Research About Interaction Between Two Tube Models Containing Spiral Magnetic Field Lines With a Little Small Length-Scale

After a long time interaction,governed by the magnetohydrodynamic(MHD)equations, between the Parker solar wind flow and a potential magnetic field combined by a dipole and a hexapole,a special streamer background structure in the solar meridian plane is presented.With the background structure,two tube models containing spiral magnetic field lines with a small length-scale can move in the computational domain step by step,interact afterward and trigger a Coronal Mass Ejection(CME)finally.The tube model is approached by a structure made up of two-dimensional co-circular magnetic field lines,with a ratio of the plasma pressure at its center to that at its edge m=2 and with a radius a for two cases:a=0.07R_s(R_s is the solar radius)and a=0.1 R_s respectively.Corresponding to the two cases,two typical numerical results are obtained.In the case a=0.07R_s,the two tube models interact with each other,merge into one set of co-circular magnetic field lines in seven solar radii and propagate outward.In the other case a=0.1 R_s,the two tube models do not merge into one and keep two sets of co-circular magnetic field lines exist in the computational domain during their propagation as a whole.