“Inverse energy cascade” may energize Jupiter’s jet streams

October 6th, 2009 - 2:26 pm ICT by ANI  

Washington, October 6 (ANI): A new analysis of Cassini observations of Jupiter shows that an “inverse energy cascade” mechanism could be supplying the energy that powers and maintains the intense jet streams that typically rip through Jupiter’s atmosphere at the same speeds as much shorter-lived hurricanes and tornadoes do on Earth.

Exactly what mechanism generates and perpetuates dozens of ferocious, relatively constant jet streams that have been observed on Jupiter over decades is a long-standing question, according to David Choi, a planetary sciences graduate student at the University of Arizona.

Earlier observational and modeling studies implied that inverse energy cascading occurs on Jupiter, he said.

“An inverse energy cascade is the transfer of energy from a local scale - local winds or small vortices, for example - to very large-scale circulations, such as big vortices and jet streams,” Choi said.

“Imagine if you took a thin coffee stirrer and stirred only one small corner of your coffee within the cup. If there is an inverse energy cascade present, the small stirring would eventually generate a big swirl that encompassed the entire cup, similar to what you would get if you were stirring with a big spoon,” he added.

“In theory, the cascade of energy on Jupiter can grow from local phenomena, such as a thunderstorm, to planetary-scale phenomena, such as the planet’s Great Red Spot or its jet streams,” he said.

His findings strengthen that idea.

Choi used a new approach in analyzing numerous images taken by the Cassini spacecraft when it flew by Jupiter in 2000 on its way to Saturn.

UA planetary sciences associate professor Adam Showman, who specializes in the study of dynamics and the evolution of planetary atmospheres, advised his research.

Choi analyzed pairs of Cassini images taken at slightly different times using automated software he developed for tracking cloud features that move with the wind.

He compiled the results, made from hundreds of Cassini images, into a near-global wind vector map of Jupiter’s atmosphere.

Further analysis of the wind vector maps disclosed new evidence that the inverse energy cascade process supplies the energy that forms and sustains Jupiter’s numerous jet streams. (ANI)

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