Relationship between formation and localization of the ionospheric sporadic E(Es) layers and the oxygen green 557.7nm line nightglow intensity

The important role of the magnitude, direction, and shear of the neutral wind in the formation and localization of sporadic ionospheric E(Es) layers, recently noted by the authors (Dalakishvili et al., JASTP, 2020; Didebulidze et al., Atmosphere, 2020; 2023; 2025; JASTP, 2025), allowed us to better understand the observed relationship between this phenomenon and the nightglow intensity of the oxygen green 557.7 nm line.

The predominantly descending tendency of the Es layers at mid-latitudes and their localization at it more observable height region (around 95-105km) of the lower thermosphere are close to the peak height (around 95km) of the volume emission rate (VER) of the 557.7nm line.

In these cases, the Es layers can be formed by neutral wind velocity with a northerly, westerly, or descending component. Such a neutral wind, can be tidal in origin or/and originate from atmospheric gravity waves (AGWs), which can also cause an increase in the green line intensity, due to increased oxygen reach downstream flux to the height of the green line luminous layer.     

Using the Barth two-step mechanism of O(¹S) excitation and estimating corresponding VER of the 557.7nm line and its integral intensity, the downward flux of neutrals caused by the tidal wind, and the approximate speed of neutral wind, the possibility of formation of Es layers and their localization at an altitude close to the luminous layer is shown.  

The emphasizes will be on the formation of Es layers during tectonic events by the influence of AGWs, which sometimes are characterized by an increase in the 557.7nm line intensity. In this case, AGWs can form Es layers and also influence the downward flux of neutral particles as they dissipate above the green line emission layer.

Acknowledgements. This study is supported by the Shota Rustaveli National Science Foundation of Georgia Grant no. FR-21-22825.