[P-PS04] Recent advances in the science of Venus

[PPS04-P02] Venusian Ionosphere During Deep Solar Minima (2016-2022): Akatsuki Radio Occulation Observations

*Keshav R Tripathi¹、Takeshi Imamura²、Raj Kumar Choudhary³、Ambili KM³ (1.JSPS International Research Fellow, Graduate School of Frontier Sciences, The University of Tokyo, Japan、2.Graduate School of Frontier Sciences, The University of Tokyo, Japan、3.SPL, VSSC-ISRO, Trivandrum, India.)

During the deep solar minimum of solar cycle 24, an investigation into the distinct characteristics of various layers within the Venusian ionosphere was conducted via a radio science experiment aboard the Akatsuki spacecraft. The unique orbital geometry of the spacecraft provided rare opportunities to explore the equatorial region of the Venusian ionosphere and atmosphere at low solar zenith angles (SZAs).
From 2016 to 2022, electron density peaked around 141 km, stable for SZAs less than 90°. Plasma density was among the lowest reported, revealing differences from Earth's Chapman variation.
Upon examining secondary ionospheric features, the V1 layer (around 125 km altitudes) demonstrated alignment with previous measurements. Akatsuki observations identified all three types of V1 layers and sporadic occurrences of the V0 layer (around 110 km altitudes) in roughly 15% of cases. Remarkably, the presence of the V0 layer was observed independently of SZA and geographical constraints [1]. Despite regular observations, nighttime occurrences of the ionosphere were infrequent. The significant findings from Akatsuki's observations of the Venusian ionosphere will be presented during the conference.

References: [1] Tripathi, K. R..., https://doi.org/10.1029/.