Based on the measurements from Radio and Plasma Wave Science instrument onboard the Cassini spacecraft over 13 years, we perform a statistical analysis of electron cyclotron harmonic (ECH) wave spatial distribution in Saturn's magnetosphere. The wave occurrence rates, amplitudes, and peak frequencies as functions of magnetic local time, L‐shell, and magnetic latitude are investigated in detail. Our results confirm that the fundamental band ECH waves mainly occur near the magnetic equator (|λ| < 5°) and also at high latitudes (20° < |λ| ≤ 40°), with averaged amplitudes of about 0.01–0.1 mV/m. By comparison, the amplitudes and occurrence rates of higher harmonics n decrease significantly, and the higher harmonic bands tend to occur at lower L‐shells along with the enhanced day‐night asymmetry. Overall, Saturnian ECH emissions are preferentially a nightside phenomenon and exhibit a gap in the midlatitude regions (5° < |λ| ≤ 20°) for the occurrence rates. The occurrence rates of ECH waves are higher at high latitudes than those near the magnetic equator, but the statistically averaged amplitudes of high latitude emissions are relatively weaker. Furthermore, the averaged peak frequencies of each ECH wave harmonic band are generally below (n + 1/2) f_ce and have the smallest deviation from (n + 1/2) f_ce near the equator. These results can be readily adopted as representative inputs to quantify the electron scattering effect of multi‐harmonic Saturnian ECH waves and investigate the underlying contribution of ECH emissions to the evolution of the Saturnian radiation belt.

中文翻译：

---

土星磁层中静电回旋加速器谐波的全球分布：13年卡西尼RPWS观测结果的调查

根据卡西尼号飞船上13年来无线电和等离子波科学仪器的测量结果，我们对土星磁层中的电子回旋加速器（ECH）波空间分布进行了统计分析。详细研究了随磁局部时间，L壳和磁纬度变化的波发生率，振幅和峰值频率。我们的结果证实，基带ECH波主要发生在磁赤道附近（| λ | <5°）以及高纬度（20°<| λ |≤40°），平均振幅约为0.01-0.1 mV /米 相比之下，高次谐波n的振幅和发生率显着降低，并且较高的谐波带往往出现在较低的L壳层上，同时昼夜不对称性增强。总体而言，土星ECH排放优先出现在夜间现象，并且在中纬度地区（5°<| λ |≤20°）出现率存在差距。在高纬度地区，ECH波的发生率要高于在磁赤道附近的ECH波，但是高纬度辐射的统计平均幅度相对较弱。此外，每个ECH波谐波频带的平均峰值频率通常低于（n  + 1/2）f _ce，并且与（n  + 1/2）f _ce的偏差最小在赤道附近。这些结果可以很容易地用作代表性输入，以量化多谐波Saturnian ECH波的电子散射效应，并研究ECH排放对Saturnian辐射带演化的潜在贡献。