- Jupiter has the most powerful planetary magnetic field in our solar system.
- It has both dipolar and non-dipolar magnetic field.
- This morphology of field is a result of Jupiter’s composition, electrical conductivity, and thermodynamic properties.
The aim of NASA’s Juno spacecraft is to understand the origin and evolution of the biggest planet of our solar system, Jupiter. Along with looking into Jupiter’s atmosphere, the probe analyzes its magnetic and gravitational fields, uncovering the planet’s internal structure.
To know what’s going on beneath the surface of the planet, it important to study its magnetic field that originates from its interior. At present, Juno is in Jupiter’s polar orbit and sending direct measurements of magnetic field close to planet’s surface.
Recently, Kimberly M. Moore and his colleague studied data from Juno and tried to prove that Jupiter’s magnetic field isn’t similar to other planets in our system. It’s significantly different in the planet’s southern and northern hemispheres. This asymmetry could have arisen due to Jupiter’s interior structure.
Before 2016, we had only a small overview of Jupiter’s magnetic field, but Juno has provided much sharper details, enabling researchers to remodel the planet’s field. The probe consists of several microwave and infrared equipment that measure thermal radiation coming from deep within Jupiter’s atmosphere.
Dipolar and Non-dipolar Magnetic Field On Jupiter
Electric currents flowing within Jupiter’s interior create a strong magnetic field around the planet. Since most of its interior consists of helium and hydrogen, the fact that it conducts electricity is really astonishing. However, the intensively high density and pressure within the planet allows hydrogen to remain in the metallic state, which can conduct electricity like other metals.
Equatorial view of Jupiter’s magnetic field | Courtesy of researchers
It takes billions of years for massive planets to cool down after their formation. In the meantime, they emit a lot of heat. Jupiter is currently emitting as much heat as it is receiving from the Sun. This heat and convection currents together blend the planet’s internal structure and form big spiral clouds and storms. Great Red Spot at the south equator is one such example.
The flow of fluid driven by convection in the interior produces a strong magnetic field by a mechanism named ‘dynamo action’. The magnetic field of Earth is generated by the same convection-steered flows but it is liquid-iron core that enables the flow of electric currents.
Both Earth’s and Jupiter’s magnetic fields are predominantly dipolar. Considering Jupiter as a bar magnet, the radial field is mostly negative (green–blue) in the southern hemisphere and mostly positive (yellow-red) in the northern hemisphere (image a).
Dipolar and non-dipolar field of Jupiter | Credit: Nature
The non-dipolar section of Jupiter’ field is presented by Moore and his team, in which they confined most of the field in the northern hemisphere (image b). Whereas, Earth has a different story: non-dipolar section is equally spread between the 2 hemispheres.
There are numerous explanations for this unique distribution of field. One of them concerns the mysterious core of the Jupiter. A few theories consider a smaller and denser core with 5 times the mass of Earth, while some assume larger and dilute core that could alter magnetic field formation.
Another explanation is the presence of stable fluid layers (one or more than one) deep inside the planet. It’s possible that these layers contain a unique composition of fluids, dividing Jupiter’s interior into different sections. For instance, if transition zones have more concentration of helium, they could change the flow of fluid inside the planet, and hence its magnetic field.
Authors have designed a model of dynamos that considers many of characteristics of Jupiter’s internal structure and atmosphere, which in turn rely on planet’s composition, electrical conductivity, and thermodynamic properties.
All these parameters have been broadly studied, but there is still a lot of uncertainties. Dynamo modellers can now efficiently test Moore’s explanations to find out whether they agree with Juno’s data. Soon, we will see a clearer picture of Jupiter’s interior.