Leveraging the unique perspective enabled by Global-scale Observations of the Limb and Disk, we examined the characteristics of equinox transitions in the thermospheric column integrated ratio of atomic oxygen to molecular nitrogen (O/N₂) in the Northern Hemisphere. We found that the timing of the O/N₂ equinox transition from winter to summer or vice versa exhibits a progression with latitude, particularly, near spring equinox. The O/N₂ equinox transition is far slower during spring compared to fall, leading to a remarkable seasonal asymmetry. Ionospheric Connection Explorer observed a prominent asymmetry in the summer-to-winter circulation in the middle to upper thermosphere, implying that the inter-hemispheric circulation plays a crucial role in the O/N₂ equinox transition. Additionally, since the wave-driven meridional circulation in the lower thermosphere displays a seasonal asymmetry between the northward-to-southward and southward-to-northward transitions, we would anticipate that the O/N₂ equinox transition is also influenced by the lower atmospheric forcing.

中文翻译：

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NASA 的 GOLD 和 ICON 任务观察到的北半球热层 O/N2 和经向环流的春分跃迁


利用全球尺度的肢体和盘观测带来的独特视角，我们研究了北半球原子氧与分子氮 （O/N ₂ ） 的温球柱积分比中的春分转变特征。我们发现 O/N ₂ 春分从冬季到夏季或反之亦然的时间表现出与纬度的演变，尤其是在春分附近。与秋季相比，春季的 O/N ₂ 春分过渡要慢得多，导致显着的季节性不对称。电离层连接探测器在中上热层的夏季到冬季环流中观察到明显的不对称性，这意味着半球间环流在 O/N ₂ 春分过渡中起着至关重要的作用。此外，由于低层热层中波驱动的经向环流在北向南和南向北过渡之间表现出季节性不对称性，我们预计 O/N ₂ 春分过渡也受到低层大气强迫的影响。