Abstract

The linear and nonlinear resonances and cascades affecting significantly the interaction of a collisionless plasma flow with a magnetic barrier and the plasma penetration into the barrier are studied using the near-Earth magnetopause as an example. Our linear theory of the membrane instability of the boundary of a magnetic barrier, the magnetopause, explains the structure of the spectra and bi-spectra of fluctuations on different segments of the boundary layers near the magnetopause and the resonances at frequencies 0.05–0.5 mHz. The recorded compressibility of waves under the magnetopause implies that their excitation by Alfv’en resonances alone is impossible. We assume, as a general principle, an approximate coincidence of the frequencies of different harmonics of different resonances as a condition for the amplification of resonances to nonlinear amplitudes and their propagation into the ionosphere. We confirm the presence of resonant waves near the magnetopause and demonstrate a nonlinear three-wave cascade interaction of compressible (0.05–5 mHz) and incompressible waves under the magnetopause that provides the excitation of resonances of magnetic field lines and waveguide resonances at frequencies 1–25 mHz without a close coincidence of the frequencies with linear resonances at the magnetopause and the bow shock. This can also provide a nonlinear coupling of linear and nonlinear resonances in other multilayered media (for example, in the plasma and neutral sheets of the geomagnetic tail and between it and the magnetopause). An example of the excitation of a waveguide mode inside the magnetopause by nonlinear membrane waves is given. We have detected a nonlinear excitation and interaction of most “magic” harmonics under the magnetopause.

中文翻译：

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等离子体绕过的磁性势垒边界的本征模：边界膜模型，线性和非线性共振以及与内部模式的耦合

摘要

以近地磁更年期为例，研究了严重影响无碰撞等离子体流与磁性屏障相互作用以及等离子体渗透进入屏障的线性和非线性共振和级联。我们关于磁障的边界的膜不稳定性的线性理论解释了磁障附近边界层不同段上的涨落的频谱和双谱结构以及在频率0.05-0.5 mHz处的共振。记录的磁层顶下的可压缩性表明，仅靠Alfv'en共振激发是不可能的。作为一般原则，我们假设 不同谐振的不同谐波的频率近似一致，以此为条件将谐振放大到非线性幅度并将其传播到电离层。我们确认了磁层顶附近存在谐振波，并证明了磁层顶下可压缩（0.05–5 mHz）和不可压缩波的非线性三波级联相互作用，从而激发了磁场线的谐振和波导在1–频率下的谐振。 25 mHz时，磁停经和船首震荡的频率与线性共振的频率并不十分吻合。这还可以在其他多层介质中（例如，在地磁尾部的等离子和中性薄片中以及在其与磁绝顶之间）提供线性和非线性共振的非线性耦合。给出了通过非线性膜波激发绝经内部的波导模式的例子。我们已经检测到在磁绝热状态下非线性激励和大多数“魔术”谐波的相互作用。