Abstract. We investigate the reflection of low-harmonic fast magnetosonic (MS) waves at the local two-ion cutoff frequency (f_cutHe+). By comparing the wave signals of the two Van Allen Probes, a distinct boundary where wave energies cannot penetrate inward are found in time-frequency domain. The boundary is identified as the time series of local f_cutHe+. For a certain frequency, there exists a spatial interface formed by f_cutHe+, where the incident waves should be reflected. The waves with small incident angles are more likely to penetrate the thin layer where the group velocity reduces significantly, and being trapped in a period of several to tens of seconds before the reflection process complete. The cutoff reflection scenario can explain the intense outward waves observed by Probe-A. These results of MS reflection at f_cutHe+ may help to predict the global distribution of MS waves and promote the understanding of wave-particle dynamics in the radiation belt.

中文翻译：

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低频快速磁声波在局部两离子截止频率处的反射：在等离子层中的观测

摘要。我们研究在局部两离子截止频率（f _{cutHe +}）下的低谐波快速磁声（MS）波的反射。通过比较两个Van Allen探头的波信号，可以在时频域中找到波能量不能向内穿透的明显边界。该边界被标识为局部f _{cutHe +}的时间序列。对于某个频率，存在一个由f _{cutHe +}，应反射入射波。具有较小入射角的波更可能穿透薄层，在该薄层处群速度显着降低，并在反射过程完成之前的数秒至数十秒的时间内被捕获。截止反射场景可以解释Probe-A观测到的强烈的向外波。MS在f _{cutHe +}处反射的结果可能有助于预测MS波的整体分布，并有助于了解辐射带中的波粒动力学。