First insights into unveiling altitude-specific dynamics and seasonal behavior of dual green line Dayglow emission regions

The atomic oxygen greenline dayglow emissions in Earth's upper atmosphere exhibit a distinct dual-peak structure, at altitudes in the range of 100–105 km and 130–145 km. These peaks are attributed to different production mechanisms, and their temporal behavior is expected to provide insights into the nature of dynamics prevalent at these altitudes. Ground-based and satellite-based measurements provide integrated information that prevents independent quantification of the contribution of emissions corresponding to these altitude regions. With the availability of a ground-based high-resolution spectrograph, MISE, capable of retrieving the daytime green line airglow emission and a collocated Digisonde operating simultaneously in Ahmedabad, there exists a unique possibility to quantify and characterize the greenline dayglow contribution in lower and upper altitude regions in terms of diurnal, altitudinal, and seasonal behavior. Investigations carried out in the present study reveal that in the lower altitude region, the emissions are strongly dependent on the electron content, underscoring the dominance of photochemical processes. In contrast, the emissions in the upper altitude region are found to be significantly influenced by meridional winds in addition to the electron content. Further, the contribution of emissions in the upper altitude region is found to be larger than that in the lower one at all times of the day and is found to vary in the range of 1.8–2.4, depending on the season. These results reveal the intriguing altitude-varying nature of the upper atmosphere in the range of 90–160 km, the details of which are presented in this work.