A Magnetohydrodynamic Simulation of the Interaction between the Solar Wind and Comet Halley

太阳风与彗星气体产生的等离子体之间的相互作用已经用三维时间相关磁流体动力学（MHD）模拟了彗星质量载荷。该模型再现了最近对哈雷彗星的探测任务所观察到的几个特征。一个微弱的弓形激波位于彗星前方3.2x10^5公里处。磁场在弱弓形激波处增加了3.7倍，并继续增加到接触面（B_<max>/B_<IMF>= 6-8）。等离子体温度在弓形激波处升高，靠近彗星处降低。行星际磁场（IMF）线挂在彗星上，形成了一条长长的等离子体尾巴，其中叶场相当强，B_<叶>/B_<IMF>-5。在尾部形成了一层致密的冷等离子体薄片，这层薄等离子体薄片的取向与IMF方向正相关。当太阳风或IMF动压发生变化时，在彗星等离子体尾部形成射线状结构和具有高等离子体压力的等离子体流，并以局部阿尔芬速度向尾部传播。这些结果解释了大量照片观测所显示的彗尾动力学。我们在太阳风-彗星相互作用中的全球MHD模拟明确了彗星质量载荷的作用，并且与太阳风与其他行星之间的相互作用进行了比较，也提供了重要的激励。

The interaction between the solar wind and the plasmas produced form cometary gases has been modeled by using a three-dimensional time-dependent magneto-hydrodynamic (MHD) simulation with the cometary mass loading. The model reproduced several features observed by the recent missions to comet Halley.A weak bow shock was located 3.2x10^5 km in front of the comet. The magnetic field increased by a factor of 3.7 across this weak bow shock and continued to increase up to the contact surface (B_<max>/B_<IMF>= 6-8). The plasma temperature increased across the bow shock and decreased nearer to the comet. Interplanetary magnetic field (IMF) lines were hung up on the comet and formed a long plasma tail in which the lobe field was quite strong and B_<lobe>/B_<IMF>-5. A cold dense plasma sheet formed in the tail and this thin plasma sheet was oriented normal the IMF direction.Ray-like structure and a plasmoid with high plasma pressure are formed in thecometary plasma tail and propagate tailward with a local Alfven speed, when the dynamic pressure of solar wind or the IMF changes. These results give an explanation on the dynamics of cometary tail which were shown by the observationsusing a lot of photos. Our global MHD simulation in the solar wind-comet interaction has made clear the role of cometary mass loading and also has given animportant incitement in comparison with the interaction between the solar wind and other planets.