The background cold electron density plays an important role in plasma and wave dynamics. Here, we investigate an event with clear modulation of the particle fluxes and wave intensities by background electron density irregularities based on Van Allen Probes observations. The energies at the peak fluxes of protons and Helium ions of 100 eV to several keV are well correlated with the total electron density variation. Intense electromagnetic ion cyclotron (EMIC) and magnetosonic (MS) waves are simultaneously observed in the high‐density regions and disappear in low‐density regions. Based on the linear theory of wave growth, the EMIC waves are generated by the ~10 keV protons, while most MS waves are generated by the positive gradient of proton phase space density at several hundred eV in the high‐density regions. Our results indicate the importance of background plasma density structures in generation of plasma waves by unstable ion distributions.

中文翻译：

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内磁层中背景电子密度的不规则性对等离子体和波的调制

背景冷电子密度在等离子体和波动力学中起重要作用。在这里，我们研究基于Van Allen Probes观测的背景电子密度不规则性对粒子通量和波强度的清晰调制的事件。质子和氦离子的峰值通量为100 eV到几keV时的能量与总电子密度变化密切相关。在高密度区域同时观察到强烈的电磁离子回旋加速器（EMIC）和磁声（MS）波，在低密度区域同时消失。基于波增长的线性理论，EMIC波是由〜10 keV质子产生的，而大多数MS波是由高密度区域中几百eV的质子相空间密度的正梯度产生的。