Solar activity variations in the composition of the low- and mid-latitude ionosphere-thermosphere system

Having a comprehensive understanding of the ionosphere's irregular behavior and its response to solar activity is crucial for satellite communication and navigation applications. The sun's extreme ultraviolet (EUV) and ultraviolet (UV) radiation are the primary sources of energy for the Earth's thermosphere and ionosphere (TI). To understand the global response of TI parameters (e.g., O/N2, and the peak electron density (Nmax)) to changes in solar irradiance, various data have been used. These include the Global-Scale Observations of the Limb and Disk (GOLD) ultraviolet imaging spectrograph, solar radio flux F10.7, predictions from the Coupled Thermosphere Ionosphere Plasmasphere electrodynamics (CTIPe) model, and International Global Navigation Satellite System Service total electron content maps (TEC). The comparison between these measurements shows that the CTIPe model successfully reproduces the behavior of the low- and mid-latitude ionosphere during both low and high solar activity. The study also investigated the delayed ionospheric TEC response against solar flux variations within the 27-day solar modulation. It was observed that the delay is less than one day, which was also confirmed in model simulations. Furthermore, the model simulations showed that the ionospheric time delay is significantly affected by various physical processes such as diffusion, photodissociation, solar and geomagnetic activities, and wave dynamics.