Winds, Rings, and Magnetism in Jupiter

From the lecture Series: A Field Guide to the Planets

By Sabine Stanley Ph.D., John Hopkins University

Magnetism in Jupiter is one of the strongest forces in the solar system, created as a result of motion, pressure, and heat. Even though Jupiter has no metal, rock, and no solid surface, it can turn hydrogen into a perfect electrical conductor. Thus, the base of magnetism is created, but what else is there to form such a huge magnetic structure?

Image shows the rings of Jupiter.
Magnetism in Jupiter is one of the strongest forces in the solar system.
(Image: cristiano tomazzolli/Shutterstock)

Missions to Jupiter

The Juno mission, a polar orbiter, arrived at Jupiter in July of 2016 and sent back detailed images of its poles. The data revealed constant turbulence in Jupiter’s atmosphere and central polar cyclones. The north pole has a ring of eight more cyclones surrounding it, while the south has a ring of five surrounding cyclones. Storms are common phenomena, but on Jupiter, they are enormous and sometimes last hundreds of years.

The image shows the internal structure of the Jupiter planet.
Jupiter gets denser and hotter toward the core, like other planets, but the winds at lower levels are slowed down, not just by high density.
(Image: Diego Barucco/Shutterstock)

In 1992, when comet Shoemaker-Levy 9 broke up into many pieces and eventually impacted Jupiter, scientists could look into the deeper levels of Jupiter’s atmosphere. Sulfur-rich compounds, ammonia, and water were revealed, along with traces of iron, magnesium, and silicon that could have belonged to the comet.

In 1995, the Galileo mission collected information from the depth of 140 kilometers before the 22-bar pressure crushed it. The probe entered a mysterious hot spot of dry and rising air, with high-speed winds, water moisture, and lightning.

In 2017 and 2018, Juno mission scientists determined that the Great Red Spot—the biggest hurricane on Jupiter since 1830—is about 350 kilometers deep. They also gained some insight into the jet streams.

Learn more about Neptune: Windy with the wildest moon.

The Rings and Winds in Jupiter

The white and red-brown rings around Jupiter are jet streams that reach as much as 3000 km into the planet. Jupiter’s gravity field was used to determine these depths. As Jupiter rotates, so do the particles around the planet. Gravitational forces pull the gas toward the center of the planet, the pressure forces from the other gas particles affect them, and rotational centrifugal forces push the gas away from the rotation axis of the planet. A balance between these factors determines the distance that a gas particle orbits.

The difference of speed among these jet streams creates zones with different centrifugal forces, mass distribution in the interior, and varying gravitational acceleration in different regions. Thus, the changes in the motion of Juno due to changes in gravitational forces show the depth of jet streams on the planet. The 3000-kilometer root of the jet streams covers around 4% of Jupiter’s radius. What happens below the jet streams?

This is a transcript from the video series A Field Guide to the Planets. Watch it now, on The Great Courses Plus.

Magnetism in Jupiter

At deeper levels on Jupiter, winds are much weaker. Increasing density is one reason, and the other is magnetism in Jupiter. Even though there is no solid metal on the planet, extreme heat and pressure create a new phase for hydrogen called the liquid metal. At a pressure of around 1,000,000 bars, i.e., one million times stronger than Earth’s surface pressure, and a temperature of about 1700°C, hydrogen atoms are so closely pressed that electrons are no longer bound to a specific proton-nucleus. Thus, liquid hydrogen becomes a very good electrical conductor.

The image shows Jupiter's magnetic field.
Jupiter’s magnetic field is like Earth’s, a dipolar field, but about ten times stronger.
(Image: pippeeContributor/Shutterstock)

The electric current creates a magnetic field that slows down winds in Jupiter’s interior. Magnetism in Jupiter was discovered in 1955, with detection of radio emissions from Jupiter.

The high-energy particles spinning around Jupiter’s magnetic field lines release radio waves as a result of their acceleration. Jupiter’s magnetism is studied by spacecraft missions carrying special instruments, known as magnetometers.

Learn more about Pluto and Charon: The binary worlds.

Jupiter’s Magnetic Field

Jupiter’s magnetic field is about ten times stronger than Earth’s magnetic field at its Earth-equivalent surface. It is a dipolar field, like Earth’s, which acts as a brake for spinning fluids on the planet and slows down the jet streams and winds.

The result of such a huge and strong magnetic field is undoubtedly the magnetosphere. Jupiter’s magnetosphere is uniquely powerful in the solar system, and its effects reach millions of kilometers beyond the planet.  

Common Questions about Magnetism in Jupiter

Q: How strong is Jupiter’s magnetic field?

Jupiter’s magnetic field is a dipolar field around ten times stronger than the Earth’s magnetic field, at the same conditions as the Earth. Magnetism in Jupiter results from electric currents in the liquid metal hydrogen, created at extremely high pressures and temperatures.

Q: Why is Jupiter so radioactive?

In 1955, radio waves were detected from Jupiter. Scientists explain that the radio emissions are caused by high-energy particles that spiral along Jupiter’s magnetic field lines. They emit radio waves due to their acceleration. Thus, magnetism in Jupiter is accompanied by radiation.

Q: What causes magnetic fields in planets?

Specifically, magnetism in Jupiter is created initially due to the extreme pressure that creates liquid metal on the planet. The atoms of hydrogen are pressed so close to each other that electrons freely move from atom to atom and are not bound to a single nucleus.
The resulting electric currents generate magnetic fields.

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