Modeling Magnetism Mighty Jupiter

Jupiter's magnetosphere is the largest structure inside our solar system (excluding the Sun of course). Jupiter has a rather strong magnetic field which is similar to Earth but about 10 times stronger.

To generate a magnetic field a planet needs a conducting fluid. Earth has molten iron core which does this job, while Jupiter has something called "metallic hydrogen". Theoretical and computational studies show that at the enormous temperature and pressure inside Jupiter hydrogen transforms into a conducting fluid state (hence the name "metallic" hydrogen). This should happen gradually as we go inside Jupiter, i.e. the fluid in Jupiter becomes more and more conducting as we go deeper and deeper.

You need to understand a small concept for the following part to make some sense. Good conductors (like metals) interact with magnetic fields while insulators (like plastic) do not.

When you look at Jupiter through telescope you will easily notice the "bands" of very strong east-west winds. This windy region does not interact with Jupiter's magnetic field because it is an insulator (like plastic or sand). But keep in mind that as we go inside Jupiter the fluid gradually becomes conducting, so at some depth these strong winds should start interacting with magnetic field. Very deep inside Jupiter, however, we have many reasons to believe that such winds can not exist.

Modelling the interaction of strong winds and inner magnetic field means modelling the highly conducting deep region of Jupiter as well as the outer surface layers where fluid starts to behave like an insulator. This was not possible in the past due to limited computational horsepower.

Recently, my colleagues simulated a model which does exactly this. These simulations are highly complex and take months on supercomputers! The image attached below shows how the magnetic field (grey tubes) looks like inside the simulation (a model Jupiter). The colours represent the magnetic field strength on various surfaces. In the very deep the magnetic field looks like mushed noodles and they come out near the poles of Jupiter. The interesting part is in the region which I have marked with a black arrow.  These grey tubes are trying to wrap around "Jupiter". This is because fast winds in this simulation are trying to go inside but magnetic field doesn't want that. In the outermost part of the simulation fluid is insulating and winds exist because it doesn't care about magnetic field. In the innermost part of the simulation fluid is highly conducting and it strongly interacts with magnetic field which kills these winds.

Twisty things happen when the fluid is not so conducting but not so insulating either. Here both winds and magnetic field reach a truce. In this region magnetic field wants to stay more-or-less parallel and winds also want to flow and wrap around. In this process of tug-of-war, magnetic field gets stretched like rubber bands and the strength of the winds gets reduced. This interesting feature was never seen in earlier simulations.

The awesome part is that +NASA's  Juno spacecraft due to arrive on Jupiter in 2016 will be able to detect these features in Jupiter's magnetic field if they exist! Confirmation from Juno will help us a lot in modelling magnetic fields in exo-planets and stars.
Modeling Magnetism ScienceSunday SciSunRR  sciencesunday ScienceSunday Mighty Jupiter
Modeling Magnetism ScienceSunday SciSunRR  sciencesunday ScienceSunday Mighty Jupiter


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