Causes of hexagonal shape of Saturn's jet stream

Question

NASA has just shown a more detailed picture of the hexagonal vortex/storm on Saturn:

http://www.ibtimes.com/nasa-releases-images-saturns-hexagon-mega-storm-may-have-been-swirling-centuries-1496218
https://en.wikipedia.org/wiki/Saturn_hexagon

Is that theoretically understood what is the cause behind this eye-catching nontrivial, regular yet not circular, shape? If so, what is the cause? I expect some explanation in terms of "nonlinear equations" of "mathematical physics" and "solitons".

P.S. (added a day after this question and the first answer was posted): On my blog where I posted the same question, people came up with some articles and phrases like "Rossby waves" and "resonance of latitude-dependence Coriolis frequency".

This post imported from StackExchange Physics at 2014-06-07 05:15 (UCT), posted by SE-user Luboš Motl

Comments

I don't think solitons are relevant for this phenomenon

This post imported from StackExchange Physics at 2014-06-07 05:15 (UCT), posted by SE-user Christoph

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Interesting, can you use the same method to create pentagons and octagons?

This post imported from StackExchange Physics at 2014-06-07 05:15 (UCT), posted by SE-user Jitter

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I've already answered this question here, though I won't repost it as hdhondt already has addressed the issue with the same reference.

This post imported from StackExchange Physics at 2014-06-07 05:15 (UCT), posted by SE-user Manishearth

Answer 1

I doubt if anyone has come up with a complete explanation, but some laboratory simulations have created similar patterns. They happen if the central and surrounding areas in a flat, circular disk of fluid have different velocities. Emily Lakdawalla at The Planetary Society covers it at this site. She also explains how other patterns (triangles & heptagons) form under similar circumstances.

This post imported from StackExchange Physics at 2014-06-07 05:15 (UCT), posted by SE-user hdhondt

Comments

Interesting, thanks.

This post imported from StackExchange Physics at 2014-06-07 05:15 (UCT), posted by SE-user Luboš Motl

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The full paper by Aguiar, Read, Wordsworth, Salter and Yamazaki is here: sciencedirect.com/science/article/pii/S0019103509004382 . It looks like they did a linear stability analysis of certain solutions of the barotropic vorticity equation en.wikipedia.org/wiki/Barotropic_vorticity_equation describing the flow in the atmosphere, which then motivated their experiments.

This post imported from StackExchange Physics at 2014-06-07 05:15 (UCT), posted by SE-user j.c.

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The experimental pictures are interesting - the hexagon arises because it's a circle being squeezed by 6 other potatoes around it. That could make sense as an approach to qualitatively explain the Z6 symmetry and why the solution is stable.

This post imported from StackExchange Physics at 2014-06-07 05:15 (UCT), posted by SE-user Luboš Motl