How Jupiter got its stripes

A new study of anisotropic two-dimensional turbulence on the surface of a rotating sphere is helping to explain the dramatic stripes on Jupiter and the other giant planets. Researchers at the University of South Florida and Ben-Gurion University of the Negev in Israel incorporated a nonzero ambient vorticity gradient into the classical theory of turbulence. Under certain conditions—including low internal friction, fast rotation, and weak forcing—they discovered that most of the energy was concentrated in alternating zonal jets highlighted by steep energy spectra. The new flow regime has not yet been produced experimentally, but the necessary conditions apply remarkably well to the upper atmospheres of the four giant outer planets of our Solar System. The researchers found that, with their relatively simple formulas, they could quantitatively model the circulation patterns on Jupiter, Saturn, and Neptune; there were insufficient data for Uranus. The new theory does not apply to Earth, which is much closer to the Sun (providing stronger forcing) and has a solid surface that can frictionally dissipate atmospheric energy. (S. Sukoriansky, B. Galperin, N. Dikovskaya, Phys. Rev. Lett. 89 , 124501, 2002 http://dx.doi.org/10.1103/PhysRevLett.89.124501 .)