Gravity Wave Modulations at the Lower Altitudes of Venus Ionosphere

Using measurements from radio science experiments onboard Venus Express and Akatsuki orbiter, we explore factors that control the occurrence and spatial structure of the electron density enhancement at lower altitudes (V-0 layer) in the Venus ionosphere. Results suggest that the Gravity Waves (GWs) play a crucial role in determining the shape of the V-0 layer. For solar zenith angle (SZA) less than 40 degrees, when the average gravity wave potential energy (AGPE) is less than 4.7 J/kg, V-0 has a single well-defined peak. For higher AGPE, the V-0 peak height gets perturbed and exhibits a wave-like structure. For SZA >40 degrees, and AGPE >4.7 J/kg, mostly wave-like feature at the base of the V-0 layer emerges. We surmise that although GW do not control the formation of a V-0 layer, they likely control its shape and occurrence altitude.