Frequency‐Dependent Modulation of Whistler‐Mode Waves by Density Irregularities During the Recovery Phase of a Geomagnetic Storm
Frequency‐Dependent Modulation of Whistler‐Mode Waves by Density Irregularities During the Recovery Phase of a Geomagnetic Storm
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DOI：
10.1029/2021gl093095
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发表时间：
2021-08
影响因子：
5.2
通讯作者：
Xu Liu;W. Gu;Z. Xia;Lunjin Chen;R. Horne
中科院分区：
文献类型：
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作者：
Xu Liu;W. Gu;Z. Xia;Lunjin Chen;R. Horne
等离子体顶附近的密度不规则是常见的现象，在哨声模波的激发和传播中起着重要的作用。在这项研究中，我们报告了在地磁风暴期间由背景密度不规则引起的哨声模式波的频率相关调制事件。高频哨声波（接近0.5fce，其中fce为赤道电子回旋频率）被捕获在密度波谷区，这是因为在平行方向附近的折射率较小，而低频哨声波（低于0.02fce）被捕获在密度波峰区，这是因为沿平行方向的折射率最大。除了调制之外，我们还定量地发现，高（低）频率哨声模式波的波幅与相对等离子体密度变化呈反相关（相关）。我们的研究表明密度不规则性动力学在控制哨声模波强度和辐射带动力学中的重要性。
Density irregularities near the plasmapause are commonly observed and play an important role in whistler‐mode wave excitation and propagation. In this study, we report a frequency‐dependent modulation event of whistler‐mode waves by background density irregularities during a geomagnetic storm. Higher‐frequency whistler waves (near 0.5fce , where fce is the equatorial electron cyclotron frequency) are trapped in the density trough regions due to the small refractive index near the parallel direction, while lower‐frequency whistler waves (below 0.02fce ) are trapped in the density crest regions due to the refractive index maximum along the parallel direction. In addition to the modulation, we also find that, quantitatively, the wave amplitude of the higher‐ (lower‐) frequency whistler‐mode waves is anti‐correlated (correlated) with the relative plasma density variation. Our study suggests the importance of density irregularity dynamics in controlling whistler‐mode wave intensity, and thus radiation belt dynamics.