Japanese scientists found that an unusually rapid rotation of the Venusian atmosphere is maintained by thermal tides, the Rossby waves and turbulence. This is the conclusion they came to based on imagery cloud layers, made with interplanetary probe “akatsuki”. Article published in the journal Science.
In the middle of last century, astronomers noticed that the upper layers of the dense cloud cover of Venus are moving much faster than its surface. While the the rotational period is 243 earth days, the atmosphere at full turn only requires 92 hours — this phenomenon is called superhottie. To maintain superrotation in need of continuous redistribution of angular momentum, which would allow to overcome the friction with the surface of the planet, however, the mechanisms underlying this process still remain unknown.
Horinouchi Takeshi (Takeshi Horinouchi) of Hokkaido University, together with colleagues examined images taken by the device “akatsuki” Japan aerospace exploration Agency JAXA. Using observations in the ultraviolet and infrared ranges from 2015 to 2018, the researchers tracked the movement of clouds and determine the speed of winds at different latitudes, and then built a global model of angular-momentum transport in the atmosphere.
The analysis showed that the angular momentum arises and is maintained by thermal tides, which represent the changes in atmospheric pressure caused by solar heating near the equator of the planet. In opposition to them are of planetary scale waves (also known as waves of rossbi) and large-scale atmospheric turbulence.