1998年11月4日至5日日冕物质抛射日地传输时间的数值模拟

在一维球坐标系下模拟了1998年11月4日至5日3个连续日冕物质抛射(CME)在行星际空间的传播和相互作用并最终形成“复杂抛射”的日地传输过程.首先在磁流体力学(MHD)数值模拟中应用Harten总变差减小(TVD)格式，通过调节计算模型中的引力无量纲参数α、等离子体参数β和气体多方指数γ，构造出数值计算所需的初态背景，使之在拉格朗日点处L1的太阳风速度vr、质子数密度Np及质子热压力与磁压力的比值βp与ACE卫星的观测数据一致.接着仅采用速度脉冲的扰动形式，其输入的幅度和持续时间由Lasco/C2、GOES、LEAR的观测数据并结合Michalek等提出的CME“锥模型”来确定.数值计算结果得到的两个激波到达时间和ACE卫星观测值的时间误差分别是3h和4h.这表明该模型能估算续发CME在行星际空间演化后驱动激波的到达时间和大致强度，在空间天气的激波到达时间的预报方面有潜在的应用价值.

A numerical simulation on the solar-terrestrial transit time of successive CMEs during November 4- 5, 1998

The solar terrestrial transit process of three successive CMEs during November 4-5, 1998 has been investigated numerically in one dimensional spherical geometry. These CMEs interact with each other while they are propagating in interplanetary space and finally form a “Complex Ejecta". A Harten's total variation diminishing (TVD) scheme is applied to solve MHD equations numerically, starting from an ambient solar wind equilibrium, with appropriate dimensionless gravity parameter α, plasma beta β, and gas polytropic index γ. The equilibrium is consistent in solar wind speed vr, proton number density Np, and the ratio of proton thermal pressure to magnetic pressure βp with the observation of ACE spacecraft at the Lagrange point(L1). Merely velocity pulse is introduced in the numerical computation, whose amplitude and duration are determined by observation data of Lasco/C2, GOES, and LEAR combined with CME's “Cone Model" proposed by Michalek et al. The results show that the differences of two shock arrival times (SATs) between the numerical calculation and the ACE observation are 3 and 4 hours, respectively. It implies that the proposed numerical model can estimate SAT and rough shock intensity formed by successive CMEs evolving in interplanetary space. Therefore the results suggest a potential application in SAT prediction for space weather.