行星际强激波与磁云相互作用的磁流体动力学模拟及其凝聚地球效应
Magnetohydrodynamic Simulation of the Interaction between Interplanetary Strong Shock and Magnetic Cloud and its Consequent Geoeffectiveness
摘要：
利用2.5维磁流体动力学（MHD）模型，在日球纬向平面内对观测到的“激波追上磁云（MC）”事件进行了数值研究。单个MC的模拟结果表明，MC旅行与恒定的整体流速。MC被注入非常强的固有磁场，在环境流中，并迅速扩大的大小最初。因此，MC的直径以渐近速度增加，而其角宽度逐渐收缩。同时，模拟了一个典型的MC和一个强的快激波从内边界产生并沿日球赤道传播的过程，两者之间相隔一定的距离。结果表明，激波首先追上前一个MC，然后穿过MC，最后与MC驱动的激波合并成一个更强的复合激波。激波阵面在行星际空间和MC体中的形态分别表现为中心凹状和光滑圆弧状。磁场的压缩和旋转是产生大磁暴的有效机制。MC被超车冲击高度压缩。间接地说，受MC影响的附带冲击波的传播时间取决于它们开始的时间间隔。当冲击波进入前一个MC核时，其最大的地球效应值也得到了相应的简化分析模型的一定程度的证实。用$Dst$指数进行量化，具体结果表明，单个MC的地质有效性大大增强，最大值增加80%。
英文摘要：
Numerical studies have been performed to interpret the observed "shock overtaking magnetic cloud (MC)" event by a 2.5 dimensional magnetohydrodynamic (MHD) model in heliospheric meridional plane. Results of an individual MC simulation show that the MC travels with a constant bulk flow speed. The MC is injected with very strong inherent magnetic field over that in the ambient flow and expands rapidly in size initially. Consequently, the diameter of MC increases in an asymptotic speed while its angular width contracts gradually. Meanwhile, simulations of MC-shock interaction are also presented, in which both a typical MC and a strong fast shock emerge from the inner boundary and propagate along heliospheric equator, separated by an appropriate interval. The results show that the shock firstly catches up with the preceding MC, then penetrates through the MC, and finally merges with the MC-driven shock into a stronger compound shock. The morphologies of shock front in interplanetary space and MC body behave as a central concave and a smooth arc respectively. The compression and rotation of magnetic field serve as an efficient mechanism to cause a large geomagnetic storm. The MC is highly compressed by the the overtaking shock. Contrarily, the transport time of incidental shock influenced by the MC depends on the interval between their commencements. Maximum geoeffectiveness results from that when the shock enters the core of preceding MC, which is also substantiated to some extent by a corresponding simplified analytic model. Quantified by $Dst$ index, the specific result gives that the geoeffectiveness of an individual MC is largely enhanced with 80% increment in maximum by an incidental shock.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
