A theoretical interpretation is given for magnetohydrodynamic (MHD) oscillations observed by the GOES and Cluster satellites on November 7, 2004 near the plasmapause (Zong et al., 2009, 2012, https://doi.org/10.1029/2009ja014393, https://doi.org/10.1029/2012ja018024), before and after an interplanetary shock passes through the magnetosphere (about 18:27 UT). It is shown that, after the shock front passage, the MHD oscillation spectra recorded by Cluster (C1) and GOES 12, located respectively inside and outside the plasmasphere, differ significantly. According to our interpretation, these differences are due to the shock wavefront affecting the plasmapause and exciting broadband resonant Alfven waves, thus significantly changing the MHD oscillation spectrum. A model in the form of a plasma cylinder was developed in order to study MHD oscillations in the dayside magnetosphere numerically. An analytical model is proposed for the source of resonant Alfven waves that has the form of two fast magnetosonic wave packets propagating along the plasmapause, resulting from the shock wave/plasmapause interaction. Numerically calculated parameters of Alfven waves excited by a source based on this model show a good agreement with the oscillation parameters observed by satellites.

中文翻译：

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等离子层顶附近激波产生的阿尔芬振荡场

对 2004 年 11 月 7 日 GOES 和 Cluster 卫星在等离子层顶附近观测到的磁流体动力学 (MHD) 振荡给出了理论解释（Zong 等，2009，2012，https://doi.org/10.1029/2009ja014393，https： //doi.org/10.1029/2012ja018024)，在行星际冲击穿过磁层之前和之后（大约 18:27 UT）。结果表明，激波锋通过后，分别位于等离子圈内外的Cluster (C1)和GOES 12记录的MHD振荡谱存在显着差异。根据我们的解释，这些差异是由于冲击波前影响了等离子层顶和激发宽带共振阿尔文波，从而显着改变了 MHD 振荡谱。为了数值研究日侧磁层中的 MHD 振荡，开发了一个等离子体圆柱形式的模型。为共振阿尔文波的来源提出了一种分析模型，该共振波具有两个快速磁声波包的形式，沿等离子层顶传播，产生于冲击波/等离子层顶相互作用。基于该模型的震源激发阿尔文波的数值计算参数与卫星观测到的振荡参数吻合良好。