Magnetosonic (MS) waves are generally considered as electromagnetic harmonic fluctuations below the lower hybrid frequency. Here we present a correlated observation of proton ring-like distribution and low harmonic magnetosonic waves with undetectable magnetic components (called QEMS). We conduct fully thermal simulations (WHAMP) to investigate the wave properties. The calculated growth rates can reproduce the observed spectral characteristics and demonstrate that the QEMS waves are excited as ion Bernstein modes by proton ring-like distribution. The ratios between the wave electric and magnetic amplitudes E/B given by WHAMP indicate that the magnetic spectral densities are below the instrument noise level, and the ratios are ∼7–80 times larger than the wave phase speeds V_ph, suggesting that the QEMS waves are essentially quasi-electrostatic, not just visually quasi-electrostatic due to the measurement limit. This study provides further insights into the QEMS natures.

中文翻译：

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准静电磁声波的观测和全热模拟

磁声 (MS) 波通常被认为是低于较低混合频率的电磁谐波波动。在这里，我们提出了质子环状分布和具有不可检测磁性分量（称为 QEMS）的低谐波磁声波的相关观察。我们进行全热模拟 (WHAMP) 来研究波浪特性。计算出的增长率可以重现观察到的光谱特征，并证明 QEMS 波通过质子环分布作为离子伯恩斯坦模式被激发。WHAMP 给出的电磁波振幅E / B比值表明磁谱密度低于仪器噪声水平，比值比波相速度大 7-80 倍V _ph，表明 QEMS 波本质上是准静电的，而不仅仅是由于测量限制而在视觉上准静电。这项研究提供了对 QEMS 性质的进一步见解。