[P-PS04] あかつきの成果と、金星科学の深化

[PPS04-02] Structure of Venus' sub-cloud atmosphere revealed by Akatsuki radio occultation experiments

*今村 剛¹、安藤 紘基²、野口 克行³、Silvia Tellmann⁴、Martin Pätzold⁴、Bernd Häusler⁵、R. K. Choudhary⁶ (1.東京大学大学院　新領域創成科学研究科、2.京都産業大学、3.奈良女子大学、4.Universität zu Köln, Germany、5.Universität der Bundeswehr München, Germany、6.Space Physics Laboratory, Vikram Sarabhai Space Center, India)

キーワード：金星、あかつき、電波掩蔽

Radio science (RS) experiment in Akatsuki mission observes the vertical structure of the Venusian atmosphere from about 35 km to 90 km altitude. Akatsuki RS mainly probes the low and middle latitude regions thanks to the near-equatorial orbit in contrast to the previous radio occultation experiments using polar orbiters. By using more than 30 profiles of the temperature and the pressure obtained by 2017, the background profiles and the local time-dependent structures were studied. The pressures below the cloud layer are systematically different from those in the Venus International Reference Atmosphere that was developed based on the measurements made by early 1980s. Significant local-time dependence of the pressure below the cloud was also seen, suggesting downward propagation of thermal tides that are generated near the cloud top. Such thermal tides can transport zonal momentum from the lower atmosphere to the upper atmosphere, thereby sustaining the super-rotation.