During sudden stratospheric warming events, the ionosphere exhibits phase‐shifted semidiurnal perturbations, which are typically attributed to vertical coupling associated with the semidiurnal lunar tide (M2). Our understanding of ionospheric responses to M2 is limited. This study focuses on fundamental vertical coupling processes associated with the latitudinal extent and hemispheric asymmetry of ionospheric M2 signatures using total electron content data from the American sector. Our results illustrate that the asymmetry maximizes at 15°N and 20°S magnetic latitudes. In the Southern Hemisphere, the M2‐like signatures extend deep into midlatitude and encounter the Weddell Sea Anomaly. The time evolution of the Anomaly exhibits a distortion, which is attributed to an M2 modulation. The hemispheric asymmetry of M2 signatures in the low latitude can be primarily explained by the transequatorial wind modulation of the equatorial plasma fountain. Other physical processes could also be relevant, including hemispheric asymmetry of the M2 below the F‐region, the ambient thermospheric composition and ionospheric plasma distribution, and the geomagnetic field configuration.

中文翻译：

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在重大的平流层突然变暖事件中，美国部门电离层Lunitidal特征的纬度变化和半球不对称性

在突然的平流层变暖事件中，电离层表现出相移的半昼间扰动，这通常归因于与半昼夜潮汐（M2）相关的垂直耦合。我们对电离层对M2的响应的理解是有限的。这项研究使用美国部门的总电子含量数据，着眼于与电离层M2标记的纬度范围和半球不对称性相关的基本垂直耦合过程。我们的结果表明，不对称性在15°N和20°S的磁纬度下最大。在南半球，类似于M2的特征延伸到中纬度，并遇到了韦德尔海异常。异常的时间演变表现出一种失真，这归因于M2调制。在低纬度地区，M2签名的半球不对称性主要可以通过赤道等离子喷泉的跨赤道风调制来解释。其他物理过程也可能是相关的，包括F区以下的M2的半球不对称，周围的热球成分和电离层等离子体分布以及地磁场构造。