Radio Scintillation and Gravity Wave Characteristics in the Venusian AtmosphereĦ½ Insights from Akatsuki Radio Occultation

Katsuyuki Noguchi, Aika Hagino (Nara Women University), 
Hiroki Ando (Kyoto Sangyo Univ.), Takeshi Imamura (Univ. of Tokyo)
SilviaTellmann, Martin Paetzold (Universitaet zu Koeln, Germany)

We investigated the relationship between radio scintillationsshort-term fluctuations in radio signal intensityand temperature fluctuations, both observed in vertical profiles from JAXA's Akatsuki radio occultation. Our results indicate that the radio scintillations and the temperature fluctuations are each strongly related to static stability: both are weaker in the low-stability layer at 5055 km and stronger in the adjacent highly stable layers. Consistent negative phase correlations above 60 km were found between the radio scintillations and the temperature fluctuations, and both quantities exhibited similar altitude-dependent attenuation trends. Assuming that the observed temperature fluctuations were generated by atmospheric gravity waves, these findings suggest that radio scintillations are likewise modulated by the same underlying gravity waves, which are likely subject to radiative damping. Using the observed temperature fluctuations, we further estimated key wave parameters, including the intrinsic frequency and the horizontal wavelength, based on the linear wave theory. The estimated horizontal wavelengths of 100300 km are consistent with previous radio occultation measurements. While optical observations by previous missions have detected similar or shorter-scale horizontal wavy structures at the upper cloud level (6070 km), their vertical wavelengths are longer than those derived in this study, suggesting that radio occultation and optical measurements capture waves with different scales. Additionally, the estimated parameters exhibit no strong dependence on local time, longitude, or latitude, and show no clear long-term variation. These results help constrain gravity wave characteristics in the Venusian atmosphere and may provide useful insights into future atmospheric modeling and communication systems for entry probes.

Noguchi et al. (2025), Journal of Geophysical Research: Planets, 130, e2025JE009149