Latitudinal Variability in OI 630.0 nm Dayglow Emissions due to Equatorial Electrodynamics and Meridional Winds over Low Latitudes

Over equatorial- and low-latitudes of the upper atmosphere, the equatorial electrodynamics has a significant role in the latitudinal distribution of plasma. Owing to this equatorial electric field in the daytime, a reduction in plasma density over equatorial latitudes and an enhancement over low-latitudes are caused. Also, its effect on the plasma distribution can be modulated by thermospheric meridional winds as they alter the height of the ionosphere. In the daytime, dynamics of the ionosphere-thermosphere can be investigated by measurements of dayglow emissions. In this work, OI 630.0 nm dayglow emissions have been used which serve as a tracer to understand the thermospheric dynamics. The OI 630.0 nm dayglow emissions are obtained by two MISE (multi-wavelength imaging spectrograph using echelle grating) operating from Hyderabad (17° N, 78° E, 9° MLAT) and Ahmedabad (23° N, 73° E, 15° MLAT) in Indian longitudes. As MISE has a large field-of-view (140°), the combined latitudinal coverage from these two MISE is 5°-18° MLAT. Investigations have been carried out for data of Jan-Feb 2020 wherein the solar flux variation was very small (68-72 sfu). Hence, this provides a unique opportunity to investigate the relative effects of the equatorial electrodynamics and meridional winds on the OI 630.0 nm dayglow emissions. The effect of the equatorial electrodynamics in the variation of OI 630.0 nm dayglow emissions is found to be nearly similar in this latitudinal range. However, meridional winds show variations with latitudes with a positive correlation near the equator and a negative correlation as one moves away from the equator. To understand such a contrast in this behaviour, simulations have been carried out which explain that the variation in the height of the ionosphere contributes to the overall dayglow emission rates. The ionospheric height closer to the equator moves into the altitude region of peak emissions offering more reactants to produce the dayglow and further away they are taken away from the region of peak production due to poleward meridional winds. The details of this study will be presented.