Research brief: Magnetic Suppression of Zonal Flows on a Beta Plane

This research was carried out by Dr Navid Constantinou prior to arriving at CLEX and is not part of the CLEX mission. However, we have included it on our website because it is a fascinating piece of science that shows how turbulent systems physics being used to understand Earth’s atmospheric, ocean and climate systems also has applications in entirely different fields well beyond our planet.

One of the most striking features of Jupiter –a gaseous giant with no solid surface – is the coloured bands encircling the planet. These bands are strong zonal jets that flow in Jupiter’s atmosphere, similar in a way to the jets in Earth’s atmosphere. Until recently, we had almost no direct observations beneath Jupiter’s clouds. But when NASA’s space probe ‘Juno’ arrived at Jupiter, we discovered that these jets continue as deep as 3,000km below Jupiter’s clouds and then terminate. (3,000km is about 5% of the planet’s radius.) This posed a new puzzle for scientists: Why do the jets penetrate as deep as they do, but no deeper? Is it merely a coincidence that the jets terminate at around the same depth at which Jupiter’s gas starts to be conducting and magnetic fields rise? Here is where our research comes in.

Using principles from statistical physics and turbulent systems, we developed a theory that describes the interaction of jets, magnetic fields, and turbulence. Within our theory, we studied the instability that forms jets when magnetic fields are present. We find that there is a threshold value of the magnetic field strength beyond which no jets can form. This offers a partial explanation as to why the jets in Jupiter terminate at 3,000km, which is about where magnetic fields start to be strong.

With a theory in hand we can further understand different phenomena that are governed by similar physics. For example, what goes on in the Sun’s interior, or even in fusion plasma experiments such as tokamaks. It’s hoped that theory and observation together will continue to give deeper insight on the physics of the universe as Juno and other probes explore and gather data from our Solar system and beyond.

By Jenny Rislund

Jenny is a Project Officer at the ARC Centre of Excellence for Climate Extremes.

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