Super-rotation of the atmosphere on Venus explained by thermal tides

Super-rotation of the atmosphere on Venus explained by thermal tides
Super-rotation of the atmosphere on Venus explained by thermal tides
Anonim

Venus is a leisurely planet, and it takes about 243 Earth days to complete a revolution around its axis. But its atmosphere is the complete opposite: unusually dense and hot, filled with poisonous sulfurous gases, it is in constant and rapid motion and rotates over the planet 60 times faster than itself, at a speed of more than 350 km / h. This super rotation should have quickly slowed down, dissipating energy, but the processes taking place in the atmosphere are constantly feeding it. The force of the winds in the atmosphere of Venus is so great that they even slightly "push" the rotation of the planet.

"Since the discovery of super-rotation in the 1960s, the mechanisms that create and sustain it have remained a mystery," says Takeshi Horinouchi of Hokkaido University. In a new article published in the journal Science, Horinuchi and his co-authors presented their explanation of the super-rotation (super-rotation) of the Venusian atmosphere, linking it to thermal tides - a pressure gradient that occurs due to uneven heating by the Sun.

The authors used data from the Japanese space probe Akatsuki (Planet-C), which was launched 10 years ago and has been operating in orbit of the neighboring planet since late 2015. The device carried out observations of the atmosphere of Venus in the infrared and ultraviolet ranges, allowing scientists to accurately figure out the speed of winds in different layers of the atmosphere and at different latitudes, and then - to compose a complete picture of the winds that support super-rotation.

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Super-rotation of the Venusian atmosphere (yellow arrow) is supported by thermal tides in the upper layers from the poles to the equator (red arrows) / © Planet-C Team

On the daytime side, watered by the close Sun, the atmosphere of Venus heats up and rushes to the night side with a powerful and constant wind flow directed along the equator. On Earth, the stabilization of such a flow is impeded by continents and oceans, "breaking" its flow. There are no oceans on Venus (although there were), and an additional increase in high-speed winds is given by the air currents of thermal tides.

The heated air in the equatorial region rises to the height and rushes in opposite directions, to the north and south poles. Accordingly, cold air from the circumpolar and temperate latitudes moves in the lower layers towards the equator, forming the Hadley circulation cell. Such cells support superfast high-altitude winds at the equator, stabilizing and accelerating their flow.

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