Global MHD simulation of the Kelvin-Helmholtz instability at the magnetopause for northward interplanetary magnetic field
Global MHD simulation of the Kelvin-Helmholtz instability at the magnetopause for northward interplanetary magnetic field
复制标题
向北行星际磁场磁层顶开尔文-亥姆霍兹不稳定性的全球 MHD 模拟
DOI：
10.1029/2009ja015193
复制
发表时间：
2010-10-09
影响因子：
2.8
通讯作者：
Hu, Y. Q.
中科院分区：
文献类型：
--
作者：
Guo, X. C.;Wang, C.;Hu, Y. Q.
通过全球磁流体动力学模拟，在行星际磁场北移期间，发现低纬磁层顶存在开尔文-亥姆霍兹（K-H）不稳定性。模拟结果呈现了磁层顶 K-H 不稳定性非线性演化的全局图景。在低纬度边界层（纬度30左右以内），由于日侧磁层顶的K-H不稳定性而产生涡旋，并沿磁层侧翼输送到较远的磁尾区；两种模式的表面波分别沿着磁层顶边界层的内缘和外缘从起始点传播到尾部区域；随着经度的增加，内模和外模的波长估计在 1 RE 到 8 RE 之间变化。涡旋在赤道平面上相对于日地线约28°的经度处发起，并且详细研究了它们沿磁层顶边界的演化。我们提出了磁层顶边界层附近内、外模表面波的特征，发现磁层顶边界两侧快模表面波的不同行为：准快模波的密度和磁场强度的变化在磁层侧（内模）是同相的，而在磁鞘侧（外模）是异相的。所获得的表面波周期与日侧磁层顶涡旋的产生周期相一致，这被认为是相应行星际条件下磁层顶的固有周期。
The Kelvin-Helmholtz (K-H) instability is found to occur at the low-latitude magnetopause through global magnetohydrodynamic simulations during a period of northward interplanetary magnetic field. The simulation results present the global picture of the nonlinear evolution of the K-H instability at the magnetopause. At the low-latitude boundary layer (within the latitude of about 30), vortices are generated by the K-H instability at the dayside magnetopause and transported to the far distant magnetotail region along the flank of the magnetosphere; two modes of surface waves propagate along the inner and outer edge of the magnetopause boundary layer, respectively, from the initial point to the tail region; the wavelengths of the inner and outer modes are estimated to vary from 1 to 8 RE as the longitude increases. The vortices are initiated at a longitude of about 28 relative to the Sun-Earth line in the equatorial plane, and their evolution along the magnetopause boundary is studied in detail. We present the characteristics of the inner and outer mode suface waves near the magnetopause boundary layer and find different behaviors of the fast-mode surface waves on the two sides of the magnetopause boundary: the variations of the density and the magnetic field strength of the quasi-fast mode waves are in phase on the magnetosphere side (inner mode), while they are out of phase on the magnetosheath-side (outer mode). The obtained period of the surface waves coincides with the generation period of the vortex at the dayside magnetopause, which is considered to be the intrinsic period of the magetopause for the corresponding interplanetary condition.