In this study, we use about 6.5 years of observation of Detection of Electromagnetic Emissions Transmitted from Earthquake Regions (DEMETER) satellite to study the spectral broadening of NWC ground transmitter signals and examine key parameters that control the width and intensity of the broadening power. First, we analyze a typical spectral broadening event, with enhanced wave intensity between lower hybrid resonance frequency and NWC signal frequency (19.8 kHz). The width and intensity of broadening power are positively proportional to the NWC wave amplitude. A following statistical analysis reveals a similar dependence on the NWC wave amplitude. The statistical analysis also indicates a significantly negative correlation of broadening spectral intensity and width with the background plasma density. The observations are consistent with existing theories predicting that lower plasma density drives a lower threshold for spectral broadening.

中文翻译：

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NWC发射器信号在电离层中的光谱展宽

在这项研究中，我们使用了大约6.5年的对从地震区发射的电磁辐射（DEMETER）卫星进行探测的观察，以研究NWC地面发射机信号的频谱展宽，并研究控制扩宽功率的宽度和强度的关键参数。首先，我们分析了典型的频谱展宽事件，在较低的混合共振频率和NWC信号频率（19.8 kHz）之间增强了波强度。扩展功率的宽度和强度与NWC波振幅成正比。以下统计分析显示出对NWC波振幅的类似依赖性。统计分析还表明，加宽光谱强度和宽度与背景等离子体密度显着负相关。