What frequencies of standing surface waves can the subsolar magnetopause support?
What frequencies of standing surface waves can the subsolar magnetopause support?
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DOI：
10.1002/2014ja020545
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发表时间：
2015-05-01
影响因子：
2.8
通讯作者：
Plaschke, F.
中科院分区：
文献类型：
--
作者：
Archer, M. O.;Plaschke, F.
有人提出，太阳下磁层顶可能支持自己的本征模，由传播的表面波组成，这些表面波在北方/南方电离层反射形成驻波。虽然这些所谓的Kruskal-Schwarzschild（KS）模式的本征频率已在典型条件下估计，但在整个太阳风条件下的潜在频率分布尚不清楚。使用模型的磁层和磁鞘适用于整个太阳周期的太阳风数据的价值，我们进行飞行时间计算产生的KS模式频率的数据库。在非风暴时期或北向行星际磁场（IMF）下，最有可能的基频计算为0.64（-0.12）（+0.03）mHz，与先前的估计和太阳下磁层顶驻波的间接观测证据一致。然而，分布表现出显着的扩展（+/-0.3 mHz的顺序）表明，KS模式的频率，特别是高次谐波，应根据太阳风的条件有很大的不同。这种大的传播观测统计的影响进行了讨论。太阳下磁层顶的本征频率被发现是最依赖于太阳风的速度，向南分量的IMF，和DST指数，与后两个是由于磁层的侵蚀重联和前者的表面波相速度的表达式的效果。最后，KS模式的可能发生被证明是由偶极子的倾斜角控制。
It is has been proposed that the subsolar magnetopause may support its own eigenmode, consisting of propagating surface waves which reflect at the northern/southern ionospheres forming a standing wave. While the eigenfrequencies of these so-called Kruskal-Schwarzschild (KS) modes have been estimated under typical conditions, the potential distribution of frequencies over the full range of solar wind conditions is not known. Using models of the magnetosphere and magnetosheath applied to an entire solar cycle's worth of solar wind data, we perform time-of-flight calculations yielding a database of KS mode frequencies. Under nonstorm times or northward interplanetary magnetic field (IMF), the most likely fundamental frequency is calculated to be 0.64(-0.12)(+0.03) mHz, consistent with previous estimates and indirect observational evidence for such standing surface waves of the subsolar magnetopause. However, the distributions exhibit significant spread (of order +/- 0.3 mHz) demonstrating that KS mode frequencies, especially higher harmonics, should vary considerably depending on the solar wind conditions. The implications of such large spread on observational statistics are discussed. The subsolar magnetopause eigenfrequencies are found to be most dependent on the solar wind speed, southward component of the IMF, and the Dst index, with the latter two being due to the erosion of the magnetosphere by reconnection and the former an effect of the expression for the surface wave phase speed. Finally, the possible occurrence of KS modes is shown to be controlled by the dipole tilt angle.