行星际慢激波的传播和演化

采用二维理想MHD模型，分别在日球赤道面(二维二分量模型)和日球子午面(二维三分量模型)内研究太阳风中慢激波的传播和演化规律．结果表明，慢激波在向外传播的过程中逐渐演化为由原慢激波和新产生的快激波构成的激波系统，该激波系统在子午面内相对慢激波源中心法线基本对称，而在赤道面内则是不对称的：快激波阵面和慢激波阵面之间存在一个切触点，该处两个激波合并，蜕化为气体激波．上述切触点相对激波源中心法线东偏，且东偏角度在激波系统向外传播过程中不断增加．初步分析表明，行星际磁场的螺旋结构是产生日球赤道面内慢激波传播和演化的东西不对称性的主要原因．

PROPAGATION AND EVOLUTION OF INTERPLANETARY SLOW SHOCK

Using a two-dimensional, ideal MHD model, this paper investigates the evolution of a slow shock in the solar wind in the heliospheric equatorial plane (2-D, 2-component model) and the heliospheric meridional plane (2-D, 3-component model) respectively. It is shown that the slow shock evolves into a shock system that consists of the original slow shock and a newly formed fast shock. The shock system is nearly symmetrical with respect to the central normal of the slow shock source in the heliospheric meridional plane, whereas it is asymmetrical in the heliospheric equatorial plane. There exists a touch point between the fronts of fast and slow shocks, at which the two shocks merge and degenerate into a gas-dynamic shock. The touch point deviates eastward with respect to the central normal of the shock source, and the deviation angle increases during the outward propagation of the shock system. A preliminary analysis shows that the east-west asymmetry of the propagation and evolution of the slow shock in the heliospheric equatorial plane is mainly attributed to the spiral structure of the interplanetary magnetic field.