Diffuse auroral electron scattering by electrostatic electron cyclotron harmonic waves in the dayside magnetosphere

Although electrostatic electron cyclotron harmonic (ECH) waves are frequently observed in the dayside magnetosphere, their effects on the formation of dayside diffuse aurora remain poorly understood. In this study, we quantitatively evaluate the efficiency of dayside ECH wave scattering in producing the electron diffuse aurora precipitation during a typical ECH wave event by calculating the quasi-linear bounce-averaged scattering rates. We find that dayside ECH waves can efficiently pitch angle scatter diffuse auroral electrons on timescales of a few hours to ~1 day over a broad range of electron energy and equatorial pitch angle, i.e., from ~300 eV to 10 keV with aeq from the loss cone to 45°. Especially for ~300 eV to 2 keV electrons, the scattering rates can even approach the strong diffusion limit, resulting in an almost fully filled loss cone. Our results confirm the significant role of ECH waves in driving the dayside diffuse aurora.

尽管静电电子回旋谐波（electrostatic electron cyclotron harmonic, ECH）波在日间磁层中频繁被观测到，但其对日间弥散极光形成的影响仍不甚明晰。本研究通过计算准线性弹跳平均散射率，定量评估了典型ECH波事件期间，日间ECH波散射引发电子弥散极光沉降的效率。研究结果表明，在电子能量约300 eV至10 keV、赤道俯仰角覆盖损失锥至45°的宽泛区间内，日间ECH波可在数小时至约1天的时间尺度上，高效散射弥散极光电子的俯仰角。尤其对于能量约300 eV至2 keV的电子，其散射率甚至可接近强扩散极限，致使损失锥几乎被完全填满。本研究结果证实了ECH波在驱动日间弥散极光过程中的重要作用。