Authors:

Aishani Das-Ghosh

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About Paper:

The atmospheric dynamics of gas giant planets differ dramatically from those on Earth, producing large, long-lived storms near their poles. Early observations of Saturn revealed a single dominant polar vortex (a circular flow), reinforcing the long-standing assumption that only one large-scale vortex can exist at each pole of a rapidly rotating gas giant'. However, subsequent observations of Jupiter by NASA's Juno mission revealed a striking departure from this picture: multiple vortices arranged in regular polygonal arrays, with eight vortices at the north pole and five at the south". How such highly organized structures emerge and persist within a strongly turbulent atmosphere remains an open question in planetary science. In earlier work, | investigated whether these vortex arrays could arise from instabilities of an initially single polar vortex. Using a simplified mathematical model of fluid motion and systematically varying key physical parameters, | showed that this scenario is unlikely to reproduce the observed polar configurations on Jupiter. Currently, we are investigating whether polar vortex lattices can instead emerge through turbulent self-organization in a rotating atmosphere. Large-scale planetary flows are well approximated as two-dimensional, a regime in which turbulence exhibits an inverse energy cascade: energy injected at small scales is transferred to larger scales, promoting the spontaneous formation of coherent structures such as jets and vortices®. To test this hypothesis, | perform high-resolution numerical simulations of the Navier-Stokes equations—which govern the conservation of momentum in fluids—on a rotating sphere. By systematically varying the planetary rotation rate and the scale at which energy is injected, | identify parameter regimes in which stable, long-lived vortex lattices emerge. These results suggest that Jupiter's polar vortices may be a natural consequence of turbulent self-organization in a rapidly rotating atmosphere.

Source:

Northwestern University

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Co-authors:

Aishani Das-Ghosh