行星际中间激波的演化  

EVOLUTION OF MHD INTERMEDIATE SHOCKS IN INTERPLANETARY SPACE

作　　者：胡小龙[1] 胡友秋[1] 

机构地区：[1]中国科学技术大学地球和空间科学系,合肥230026

出　　处：《地球物理学报》1998年第4期447-454,共8页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(49474238)

摘　　要：本文采用特征线方法和激波装配法,对磁流体中间激波在行星际空间的演化过程进行数值模拟。主要结论如下:(1) 2→4型中间激波通过向下游发出后向慢压缩波使下游态磁场减幅,通过向上游发出前向快压缩波使上游态磁场增幅,以致2→4型中间激波迅速经导灭激波向慢激波转化;所发出的前向快压缩波经非线性变陡形成快激波。(2)1→3型中间激波首先通过向下游发出前向慢稀疏波而很快变成1→3=4型临界中间激波,并瞬间转变为由前向快激波和前向2→4型中间激波构成的激波系统。其中,2→4型中间激波可在其前导快激波的下游传播较远的距离,有可能为 IAU 附近的飞船观测到,但最终导灭激波转变为慢激波。Using the method of characteristics and shock fitting techniques,this paper simulates numerically the evolution of MHD (Magnetohydrodynamic) intermediate shocks in interplanetary space.The main conclusions are:(1) For an intermediate shock of type 2→4,the downstream tangential magnetic strength decreases by launching reverse slow compression waves downstream,whereas the upstream tangential magnetic strength increases by launching forward fast compression waves upstream.Therefore,the intermediate shock of type 2→4 evolves rapidly into a slow shock via a switch-off shock.Meanwhile the forward fast compression waves become a fast shock through nonlinear steepening process.(2) An intermediate shock of type 1→3 becomes a critical intermediate shock of type 1→3=4 by by launching forward slow rarefaction waves downstream,and immediately evolves into a shock system consisting of a forward fast shock and an intermediate shock of type 2→4. The intermediate shock of type 2→4 may propagate a larger heliocentric distance in the downstream side of the leading fast shock and be observed possibly by spacecraft near 1AU,but it eventually becomes a slow shock via a switch off shock. Key words Interplanetary dynamics,Magnetohydrodynamics,MHD shock, Intermediate shock,Numerical simulation

关 键 词：行星际动力学 磁流体力学 磁流体激波 中间激波 

分 类 号：P185.9[天文地球—天文学]