行星际磁场By对弓激波影响的MHD结果

Effects of IMF By on the bow shock:MHD results

利用全球磁流体模拟的结果,本文研究了行星际磁场By对弓激波位型的影响.结果显示:随着行星际磁场By绝对值的增大,弓激波的日下点距离、旋转对称张角、南北非对称性以及旋转非对称性均随之增加.其中,By对弓激波日下点距离的影响可达5 R E左右.东向By和西向By对弓激波位型影响具有对称性,东向By和西向By大小相同时弓激波日下点距离、旋转对称张角以及旋转非对称性参数均相同,而南北非对称性参数大小相同正负相反.行星际磁场By占主导时弓激波尾部横截面在南北方向上拉伸,并且拉伸程度随着By绝对值的增大而增大,弓激波尾部横截面的拉伸现象与磁声波马赫数密切相关.

Using the global magnetohydrodynamic(MHD)simulation,we investigate the effects of the Y component of interplanetary magnetic field(IMF)By on the shape and size of the bow shock.Our results show that with the increasing absolute value of By,the bow shock′s standoff distance,the flaring angle of the rotationally symmetry,the north-south asymmetric parameter,and the rotationally asymmetric parameter all increase.The extent of the By effects on the bow shock′s standoff distance can reach 5 R E.The influences of the eastward and westward By on the bow shock are symmetric.For the same absolute value of the eastward and westward By,the bow shock′s standoff distances,the flaring angles of the rotationally symmetry,and the rotationally asymmetric parameters have the same values,while the north-south asymmetric parameters have the same absolute values but with a different sign.The bow shock tail′s cross-section is elongated in the north-south direction under By conditions,and the extent of the elongation is enhanced with increasing By.The elongation of the bow shock tail′s cross-section is closely related to the magnetosonic Mach number.