Polar cap patches are islands of enhanced electron density in the polar cap F region ionosphere, which sometimes affect the propagation of trans‐ionospheric radio waves. Considering the intake of daytime sunlit plasma by the high‐latitude convection as the primary cause of patches, the spatial overlap between the convection and the daytime sunlit plasma should be one of the critical factors controlling the generation of patches. To confirm this hypothesis, we statistically investigated the UT and seasonal distributions of patch occurrence frequency in both the hemispheres by using in situ plasma density data from the Swarm satellite. As a result, it was found that the occurrence distribution of patches is a complex function of UT, season and hemisphere, but it can be mostly interpreted by the spatial overlap between the high‐latitude convection and the solar terminator. This suggests that polar cap patches are not necessarily phenomena that occur only during winter months. That is, patches can often be observed even in periods away from the winter solstice if the location of solar terminator in the magnetic coordinate system is appropriate for the generation of patches. For example, in the southern hemisphere, where the offset between the geographic and magnetic poles is larger than that in the northern hemisphere, the highest patch occurrence rate is obtained around the equinoctial periods. These results indicate that it is needed to take these dependences into account when we discuss and predict the space weather impacts of patches on the trans‐ionospheric radio propagation.

中文翻译：

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极地补丁的出现分布：取决于UT，季节和半球

极帽斑块是极帽F区电离层中电子密度增强的岛，有时会影响跨电离层无线电波的传播。考虑到高纬度对流吸收日照血浆是斑块的主要原因，对流和日照血浆之间的空间重叠应该是控制斑块产生的关键因素之一。为了证实这一假设，我们使用来自Swarm卫星的原位血浆密度数据，对两个半球的斑块出现频率的UT和季节性分布进行了统计调查。结果发现，斑块的发生分布是UT，季节和半球的复杂函数，但是，这在很大程度上可以由高纬度对流和太阳终结者之间的空间重叠来解释。这表明极地盖帽不一定是仅在冬季出现的现象。即，如果太阳终结者在磁坐标系中的位置适合于斑块的产生，那么即使在冬至以外的时间段也经常可以观察到斑块。例如，在南半球，地理和磁极之间的偏移比北半球的偏移大，在等分周期附近可获得最高的斑块出现率。这些结果表明，当我们讨论和预测补丁对跨电离层无线电传播的空间天气影响时，有必要考虑这些依赖性。