# Causes of hexagonal shape of Saturn's jet stream

+ 9 like - 0 dislike
186 views

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

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
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
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

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

+ 8 like - 0 dislike

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
answered Dec 5, 2013 by (50 points)
Interesting, thanks.

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

 Please use answers only to (at least partly) answer questions. To comment, discuss, or ask for clarification, leave a comment instead. To mask links under text, please type your text, highlight it, and click the "link" button. You can then enter your link URL. Please consult the FAQ for as to how to format your post. This is the answer box; if you want to write a comment instead, please use the 'add comment' button. Live preview (may slow down editor)   Preview Your name to display (optional): Email me at this address if my answer is selected or commented on: Privacy: Your email address will only be used for sending these notifications. Anti-spam verification: If you are a human please identify the position of the character covered by the symbol $\varnothing$ in the following word:p$\hbar$ysicsOv$\varnothing$rflowThen drag the red bullet below over the corresponding character of our banner. When you drop it there, the bullet changes to green (on slow internet connections after a few seconds). To avoid this verification in future, please log in or register.