The footprint of radio emission from extensive air showers is known to exhibit asymmetries due to the superposition of geomagnetic and charge-excess radiation. For inclined air showers a geometric early-late effect disturbs the signal distribution further. Correcting CoREAS simulations for these asymmetries reveals an additional disturbance in the signal distribution of highly inclined showers in atmospheres with a realistic refractive index profile. This additional apparent asymmetry in fact arises from a systematic displacement of the radio-emission footprint with respect to the Monte-Carlo shower impact point on the ground. We find a displacement of \(\sim 1500\) m in the ground plane for showers with a zenith angle of \(85^{\circ }\), illustrating that the effect is relevant in practical applications. A model describing this displacement by refraction in the atmosphere based on Snell’s law yields good agreement with our observations from CoREAS simulations. We thus conclude that the displacement is caused by refraction in the atmosphere.A preprint version of the article is available at ArXiv.

中文翻译：

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用CoREAS模拟的倾斜式风淋室的无线电发射足迹的折射位移

众所周知，由于地磁辐射和电荷过量辐射的叠加，广泛的空气淋洗所产生的无线电辐射足迹显示出不对称性。对于倾斜的淋浴器，几何的早期效应会进一步干扰信号分配。纠正这些不对称性的CoREAS仿真后，发现在具有实际折射率分布的大气层中，高度倾斜的阵雨的信号分布会产生额外的干扰。实际上，这种额外的明显不对称性是由于无线电发射足迹相对于地面上的蒙特卡洛阵雨冲击点的系统性位移引起的。我们发现 天顶角为\（85 ^ {\ circ} \）的淋浴在地面上的\（\ sim 1500 \） m位移，说明效果与实际应用有关。根据斯涅尔定律，通过大气中的折射来描述这种位移的模型与我们从CoREAS模拟得到的观察结果非常吻合。因此，我们得出结论，位移是由大气中的折射引起的。该文章的预印本可从ArXiv获得。