Radio Scintillations observed with Venus Express

Radio occultation measurements at Venus have provided key insights into the structure of the planet’s atmosphere. One particularly remarkable phenomenon revealed by these observations is the presence of radio scintillations—rapid fluctuations in signal intensity. These scintillations are caused by small-scale irregularities in the atmospheric refractive index, which are associated with fine-scale density variations. A likely source of these density fluctuations is vertically propagating internal gravity waves originating from the convective layer located at altitudes between roughly 50 and 55 kilometers.

Frequency-dependent radio scintillations have been observed in atmospheric regions characterized by enhanced static stability, where the propagation of gravity waves is favored. This finding supports the interpretation that gravity waves are a plausible source of the observed scintillations. Consequently, the analysis of radio scintillations provides valuable information about the intensity and global distribution of gravity waves, as well as about the strength of the convective winds responsible for generating them.

We present the results of a scintillation analysis based on X-band radio occultation data from the mission Venus Express and compare them with earlier observations and model predictions. In addition, we discuss the expected outcomes of the forthcoming radio scintillation investigations of the mission EnVision and emphasize the advantages of combining X-band and Ka-band radio signals.