Small-Scale Gravity Waves in the Venus Atmosphere as seen by the VeRa Experiment on Venus Express

Atmospheric waves are present in the Venus atmosphere across a wide range of spatial scales and may play a significant role in the planet's energy and momentum budget. Small-scale temperature fluctuations, likely caused by gravity waves, are a common feature in the atmospheres of all planets. These gravity waves play a crucial role in redistributing energy and momentum within the atmosphere. Several instruments have detected gravity waves in the Venusian mesosphere and upper cloud region, but their role in maintaining the atmospheric superrotation is not yet fully understood.

From 2006 to 2014, the Venus Express Radio Science Experiment (VeRa) investigated the neutral atmosphere and ionosphere of Venus in Earth occultation geometry using the spacecraft's radio subsystem at two coherent frequencies, X-band (8.4 GHz) and S-band (2.3 GHz). Radial profiles of neutral number density, derived from altitudes between 40 and 90 km, are then converted into vertical profiles of temperature and pressure, assuming hydrostatic equilibrium.

VeRa atmospheric profiles in the upper troposphere and mesosphere show high variability due to atmospheric waves and turbulence. Small-scale temperature fluctuations originating from internal gravity waves with vertical wavelengths of only a few kilometers are detectable in the VeRa profiles.

The high vertical resolution of VeRa’s temperature profiles offers a unique opportunity to study small vertical temperature fluctuations that would otherwise be unobservable by any other remote sensing technique. These studies are crucial for understanding Venus's poorly constrained energy and momentum budgets.

The observed wave structures are analyzed using standard wave theory to investigate their vertical and horizontal structure as a function of latitude, altitude, and local time.