MHD wave transmission and production near the magnetopause
MHD wave transmission and production near the magnetopause
复制标题
DOI：
10.1029/ja080i013p01764
复制
发表时间：
1975-05
影响因子：
--
通讯作者：
A. Wolfe;R. Kaufmann
中科院分区：
文献类型：
--
作者：
A. Wolfe;R. Kaufmann
假设磁层顶是一个稳定的、平面的、切向的不连续面，这样我们就可以计算通过这个界面传播、反射和产生的波的振幅。计算表明，如果磁层中的波都是通过界面传播的，那么磁层与磁鞘的波功率谱密度之比应最敏感地取决于磁场强度与等离子体密度之比以及磁层顶磁场方向的变化。这些计算进行了比较，与Explorer 12测量波的周期在30 s和2 min之间。观测结果表明，在磁鞘中看到的最波功率的源附近的地球太阳线位于磁鞘或超越。在这个太阳下区域的磁层中，波能的很大一部分是由透射引起的。在距离地日线约35°的地方，磁层波的功率水平比通过稳定的闭合磁层顶传播所预测的要高得多。观测结果与Kelvin-Helmholtz不稳定性模型在远离太阳下点的区域中的波产生基本一致。
The magnetopause is assumed to be a stable, plane, tangential discontinuity so that we can calculate the amplitudes of waves that are transmitted through, reflected from, and produced at this interface. The calculations show that the ratio of magnetosphere to magnetosheath wave power spectral densities should depend most sensitively upon the ratios of field strengths and plasma densities and upon the magnetic field direction change at the magnetopause if all waves seen in the magnetosphere were transmitted through the interface. These calculations are compared with Explorer 12 measurements of waves with periods between 30 s and 2 min. The observations show that the source of most wave power seen in the magnetosheath near the earth-sun line lies in the magnetosheath or beyond. Transmission could account for a substantial fraction of the wave power seen in the magnetosphere in this subsolar region. Beyond about 35° from the earth-sun line, magnetosphere wave power levels are much higher than is predicted by transmission through a stable closed magnetopause. The observations are generally consistent with a Kelvin-Helmholtz instability model of wave production in this region well away from the subsolar point.