We can finally know how Jupiter’s strange polar storms live together

Jupiter, dense with chaotic clouds and raging with wild winds, is famous and beloved for its spectacular stormy atmosphere. Ever since the Juno space probe arrived there in 2016, we had unprecedented reach that helped us understand what drove the gas giant’s weather.

But Juno has not only answered, but has also asked more questions. Until the Juno mission, we were not able to get a good look at Jupiter’s poles. What the space probe saw was a jaw-dropper: a polygonal arrangement of storms, both north and south, orbiting a storm in the center.

At the North Pole of Jupiter, nine cyclone rages, one in the center, and eight others were neatly located around it, all rotating in a counterclockwise direction.

At the South Pole, Juno saw six hurricanes in 2016, one in the center, and five around it. The seventh storm joined sometime in 2019, so there are now six vortices in hexagonal shape around the central storm. These southern storms are all rotating clockwise.

Since 2016, these huge storms – comparable in size to the mainland United States – have been continuous, uneven. And now, as laid out in a new paper, we may finally have a clue as to why.

Jupiter’s system is different from Saturn, the other gas giant in the solar system, which has a single, huge storm at each pole. It is also the opposite of processes occurring on Earth – on our planet, most cyclones form at tropical latitudes, and flow toward the poles, but they spread over land and cold oceans before they get there.

Since Jupiter has neither land nor cold oceans, it is understandable that its storms will behave differently from Earth, but the question is, why do they not merge to form single storms?

Astronomer Cheng Li of the University of California, Berkeley, and their colleagues at Caltech ran numerical simulations of hurricane configurations, and discovered a set of conditions under which hurricanes can persist for long periods of time and without a brush in the mega Together- storm.

This is basically the “Goldilocks zone” for the Jovian storm.

“We find that the stability of the pattern depends mostly on shielding – an anticyclonic ring around each cyclone – but also on depth,” the researchers write in their paper.

“Very little shielding and small depths lead to the merging and loss of polygon patterns. Too much shielding causes the cyclonic and anticyclonic parts of the vortex to separate. Stable polygons exist in the middle.”

The team used equations that describe the motion of a layer of fluid on a sphere, and model the polygon arrangement of vortices. This is not new, but the team added polar geometry and beta drift – the tendency of cyclones to drift due to increased Coriolis force due to wind speed – in their model, to play on Jupiter for a more detailed understanding of dynamics .

According to their findings, two things happen in the game, and the situation should be fine for both. The first is, to some extent, the depth of the cyclone – how far it reaches in the Jovian atmosphere. Too shallow, and the storms will dissolve.

But the biggest effect on the sticking power of the storm is a phenomenon known as vortex shielding. This is when the vortex – in this case, our Jovian cyclone – is surrounded by a ring rotating in the opposite direction. So, each counterclockwise cyclone at the North Pole is surrounded by a powerful wind around the cyclone in a clockwise direction.

If this preservation is too weak, the storms will dissolve. If it is too powerful, the storm and its shields will break apart from each other, making the total storm a mess. Therefore, to maintain both the depth of the cyclone and the strength of their vortex gradient, one must be just right.

And thus, another set of mysteries.

“There are many questions we have not answered,” the researchers wrote.

“We have not figured out how cyclones are formed – whether they create space or rise above lower latitudes. Furthermore, we have not stated how a steady state is maintained – the number of cyclones over time. Why it does not grow. Also, we. It is not determined how shielding develops, or why only the Jovian vortex is shielded. ”

The team has yet to test its model on the actual Juno data. However, by doing so we can find some answers to these deeply complex questions.

Has been published in Proceedings of the National Academy of Science.