This page is your guide to Jupiter’s magnetic field — what it is, how it works, and why it shapes everything in the Jovian system, from Io’s volcanoes to Ganymede’s own little magnetic bubble. To learn about Jupiter as a whole, see the main Jupiter pillar.
Jupiter’s magnetic field is an invisible field of magnetism around the planet, generated deep inside Jupiter by a layer of liquid metallic hydrogen. It is the strongest planetary magnetic field in our solar system. Its magnetic moment is often described as about 20,000 times stronger than Earth’s, and it creates a giant bubble around Jupiter called the magnetosphere, which traps radiation and shapes Jupiter’s breathtaking auroras.
Hold a small magnet near a fridge door. Feel how it pulls and pushes? That is a magnetic field at work. Now imagine that field stretching millions of kilometres through space, glowing with auroras at the poles, and powerful enough to make a moon’s atmosphere strip away. That is Jupiter’s magnetic field — the same physics, scaled up to planet size.
MAGNETOSPHERE — the giant bubble-shaped region around a planet where its magnetic field controls charged particles. Every planet with a magnetic field has one. Jupiter’s is the biggest planetary magnetosphere in the solar system.
📋 Jupiter’s magnetic field — Quick Facts
- Strongest planetary fieldIn the solar system — magnetic moment about 20,000× Earth’s
- Field strength at the cloud topsAround 4–20 Gauss in different places (Earth’s surface field is about 0.5 Gauss)
- What generates itLiquid metallic hydrogen swirling deep inside Jupiter
- Magnetosphere sizeThe largest planetary magnetosphere in the solar system — if visible from Earth, it would appear larger than the full Moon
- Magnetotail lengthCan stretch almost to, or even past, Saturn’s orbit, depending on solar-wind conditions
- Discovered byPioneer 10 spacecraft, December 1973
- Most-studied recently byNASA’s Juno mission (2016–) using two magnetometers
- AurorasMost powerful planetary auroras in the solar system — around 100 terawatts of total power
- Aurora coloursVisible in ultraviolet, infrared, visible light, and X-ray — multi-spectrum
- Big magnetosphere contributorJupiter’s moon Io — pumps roughly 1,000 kg of material into the magnetosphere every second
Magnetism itself is not the dangerous part. The danger for spacecraft comes from charged particles trapped inside Jupiter’s magnetosphere. Those particles create intense radiation that can damage electronics. Throughout this page, “radiation” and “magnetic field” mean different things — the field is the invisible force, the radiation is the fast-moving particles caught inside it.
What is a magnetic field?
A magnetic field is an invisible force around something that pushes or pulls on other magnetic things. You feel it whenever you stick a fridge magnet onto metal. Magnetic fields are made by moving electric charges — inside a small magnet, the charges are tiny electron motions; inside Earth or Jupiter, they are huge currents of churning liquid metal.
Most planets that have magnetic fields have a liquid metallic layer deep inside them. On Earth, that layer is molten iron. On Jupiter, it is something even stranger: a vast ocean of liquid metallic hydrogen — hydrogen gas squeezed so hard by Jupiter’s gravity that it behaves like a metal and conducts electricity. That layer rotating along with Jupiter is what powers the planet’s magnetic field.
METALLIC HYDROGEN — ordinary hydrogen squeezed so hard that it stops being a gas and starts behaving like a liquid metal, able to conduct electricity. Scientists believe Jupiter has a huge ocean of metallic hydrogen deep below its clouds. That ocean, rotating with the planet, is what makes Jupiter’s incredibly strong magnetic field.
How strong is Jupiter’s magnetic field?
Jupiter’s magnetic field is the strongest planetary magnetic field in our solar system. Different sources give different ways of describing how strong it is, depending on what is being measured. The most common comparison is magnetic moment — a single number that captures the whole field at large scales — and Jupiter’s magnetic moment is roughly 20,000 times stronger than Earth’s.
At Jupiter’s cloud tops, the field strength varies between about 4 and 20 Gauss in different places (Earth’s surface field is about 0.5 Gauss). NASA’s Juno spacecraft was the first to measure it up close, and it found the field was even stronger and more lumpy than scientists had predicted before — not a smooth oval shape, but irregular, with strong patches and weaker ones.
The magnetosphere — the giant bubble of magnetism around Jupiter — is so big that if our eyes could see magnetism, it would look larger than the full Moon from Earth. It is the largest planetary magnetosphere in the solar system. And the magnetotail — the bubble’s long downstream tail — can stretch almost to, or even past, Saturn’s orbit, depending on solar-wind conditions.
A compass on Earth gently points north. Near Jupiter, that same compass would be overwhelmed by a magnetic field far stronger and much more uneven than Earth’s. It would not behave like a normal compass at all — the field is so lumpy that the needle might swing in unexpected directions depending on where you stood.
Jupiter’s auroras — the most powerful planetary auroras
Earth’s northern and southern lights are beautiful. Jupiter’s blow them away. Jupiter’s auroras are the most powerful planetary auroras in the solar system, glowing constantly around the planet’s poles in ribbons hundreds of kilometres tall and putting out roughly 100 terawatts of total power — more than every electricity-generating power plant on Earth combined.
What causes them?
Just like on Earth, Jupiter’s auroras happen when fast-moving charged particles crash into atoms high in the planet’s atmosphere. As the particles hit the atoms, they release energy as light — in ultraviolet, infrared, visible, and even X-ray wavelengths.
But Jupiter’s auroras have one big difference from Earth’s. On Earth, most aurora energy comes from the Sun — charged particles streaming from the Sun (the “solar wind”) hit Earth’s magnetic field, get caught, and flow toward the poles. On Jupiter, much of the aurora energy comes from Jupiter itself — and from its moon Io. Io supplies huge amounts of charged material that helps feed Jupiter’s magnetosphere and aurora system.
Why are they pulse-like?
Scientists have observed Jupiter’s X-ray auroras pulsing on regular timescales — sometimes around tens of minutes between pulses. For years this was a puzzle. Recent research using both NASA’s Juno spacecraft and Earth-orbiting X-ray telescopes suggests these pulses come from tiny vibrations in Jupiter’s magnetic field, which set off waves that crash into the atmosphere. The exact mechanism is still being studied.
Most of what we know about Jupiter’s magnetic field up close comes from NASA’s Juno spacecraft, which carries two magnetometers on a long boom and measures Jupiter’s field 60 times a second. Juno was the first spacecraft to orbit Jupiter’s poles, so it has been able to see the auroras from above in a way no previous mission ever could. Read more about Juno →
The moons inside Jupiter’s magnetic bubble
All of Jupiter’s big moons orbit inside the magnetosphere. That means they are constantly bathed in charged particles trapped by Jupiter’s magnetic field. This has huge effects on the moons — and, in one famous case, the moons have a huge effect back on the magnetic field.
Io — the moon that feeds the magnetosphere
Io, the most volcanically active world in the solar system, blasts about 1,000 kilograms of sulfur dioxide and other material into space every second. That material gets ionised (turned into charged particles) and trapped by Jupiter’s magnetic field, forming a giant ring of plasma around Jupiter’s orbit called the Io plasma torus. Io’s material supplies much of the charged material that helps feed Jupiter’s aurora system.
Ganymede — a moon with its own magnetic bubble
Ganymede, the biggest moon in the solar system, is the only moon known to generate its own magnetic field. That gives Ganymede its own little magnetic bubble — a tiny magnetosphere inside Jupiter’s much bigger one. Where the two bubbles meet, the interaction creates Ganymede’s own auroras at its poles.
Europa and Callisto — induced magnetic fields
Europa and Callisto do not generate their own intrinsic magnetic fields. But they each contain a salty hidden ocean (or in Callisto’s case, possibly one), and Jupiter’s magnetic field passing through that ocean creates a small induced magnetic field — like an electric current in a wire. This is one of the main pieces of evidence that those moons have salty water underneath. Ganymede has its own intrinsic field and shows induced ocean signatures too, which is part of why scientists are confident it has a hidden ocean.
The Io plasma torus — the donut-shaped ring of charged particles fed by Io’s volcanoes — glows in visible light. It can even be detected with sensitive Earth-based telescopes. Io is literally painting Jupiter’s magnetosphere with its volcanic eruptions, every second of every day.
How was Jupiter’s magnetic field discovered?
Scientists guessed Jupiter might have a magnetic field even before any spacecraft visited — because in the late 1950s, radio astronomers detected strange radio signals coming from Jupiter. Radio emissions like these usually come from charged particles trapped in a magnetic field. But there was no way to confirm it from Earth alone.
In December 1973, NASA’s Pioneer 10 became the first spacecraft to fly past Jupiter — and the first to measure Jupiter’s magnetic field directly. Its instruments confirmed everything astronomers had suspected: a vast, intense magnetic field surrounding the giant planet.
Every Jupiter spacecraft since then has carried instruments to study the magnetic field: Pioneer 11 (1974), the two Voyagers (1979), the Galileo orbiter (1995–2003), and Juno (since 2016). Future missions — Europa Clipper and JUICE — will continue adding to what we know.
Jupiter’s magnetic field comes from iron, just like Earth’s.
Jupiter doesn’t have a metal iron core like Earth’s. Its magnetic field comes from a deep ocean of liquid metallic hydrogen — hydrogen squeezed so hard by Jupiter’s gravity that it conducts electricity like a metal. Same physics (electric currents in a moving liquid), different material.
Why does Jupiter’s magnetic field matter?
Jupiter’s magnetic field is not just a curiosity — it is one of the most important things to know if humans ever want to send spacecraft or people to Jupiter’s system.
- It traps dangerous radiation. Inside the magnetosphere are particles moving at near-light speeds that can damage spacecraft electronics. NASA’s Juno and Europa Clipper carry titanium radiation vaults specifically to survive it.
- It explains the moons. Induced magnetic fields in Europa, Ganymede, and Callisto are how scientists discovered the moons probably have hidden oceans.
- It links Jupiter and Io. Io’s volcanoes feed Jupiter’s magnetosphere, which then shapes the radiation environment for every moon.
- It teaches us about other planets. Studying Jupiter’s field helps scientists understand exoplanets — giant planets around other stars — which often have strong magnetic fields too.
Jupiter’s magnetic field is a great way to connect lots of topics at once: planetary interiors (metallic hydrogen), particle physics (charged particles & auroras), Earth’s own magnetic field (compare and contrast), and habitability (induced fields revealing hidden oceans). Ask students: if a moon’s induced magnetic field tells us about its hidden ocean, what kind of detective work is that? (Magnetic ocean detection — it’s how Galileo orbiter first hinted at oceans in Europa, Ganymede, and Callisto.)
Frequently asked questions about Jupiter’s magnetic field
How strong is Jupiter’s magnetic field?
It is the strongest planetary magnetic field in our solar system — around 20,000 times stronger than Earth’s at large scales. At Jupiter’s cloud tops, the field strength varies between about 4 and 20 Gauss in different places (Earth’s surface field is about 0.5 Gauss).
What creates Jupiter’s magnetic field?
A huge layer of liquid metallic hydrogen deep inside Jupiter. Under the planet’s extreme pressure, hydrogen gas stops being a gas and starts behaving like a liquid metal. As that layer rotates with Jupiter, it acts like a giant electrical generator — producing the planet’s powerful magnetic field.
What is the magnetosphere?
The magnetosphere is the giant bubble of magnetism around Jupiter, shaped by its magnetic field. It is so large that if our eyes could see magnetism, it would look bigger than the full Moon from Earth. The magnetosphere’s long tail stretches past Saturn’s orbit.
Does Jupiter have auroras like Earth?
Yes — only much, much more powerful. Jupiter’s auroras are the most powerful in the solar system, putting out about 100 terawatts of total power. They glow in ultraviolet, infrared, visible, and X-ray light, and they happen at both of Jupiter’s poles.
Why are Jupiter’s auroras so different from Earth’s?
On Earth, most of the energy for auroras comes from the Sun. On Jupiter, much of the energy comes from Jupiter itself — and from the moon Io, whose volcanoes blast about 1,000 kg of material into Jupiter’s magnetic field every second. That makes Jupiter’s aurora system fundamentally different from ours.
When was Jupiter’s magnetic field discovered?
Astronomers detected unusual radio signals from Jupiter as early as the late 1950s, hinting at a magnetic field. The first direct measurements came in December 1973, when NASA’s Pioneer 10 spacecraft flew past Jupiter and confirmed a powerful magnetic field surrounding the planet.
Do Jupiter’s moons have their own magnetic fields?
Only Ganymede generates its own intrinsic magnetic field — the only moon in the solar system known to do this. Europa and Callisto show induced magnetic-field signals that may come from salty hidden oceans (Jupiter’s field passing through their oceans creates a small response, like an electric current in a wire). Ganymede also shows induced ocean signatures from Hubble aurora measurements on top of its intrinsic field. Io does not have its own field.
What is the Io plasma torus?
A giant donut-shaped ring of charged particles around Jupiter, fed by Io’s volcanoes. About 1,000 kg of material flows into the ring from Io every second. The torus is so dense and energetic that it can even be detected with sensitive Earth-based telescopes.
Is Jupiter’s magnetic field dangerous?
For spacecraft, yes — the radiation trapped by the magnetic field can damage electronics quickly. That’s why Juno and Europa Clipper carry titanium radiation vaults. For Earth and people on Earth, no — we are far too far away. Jupiter’s field stays at Jupiter.
Is Jupiter’s magnetic field the same as radiation?
No. A magnetic field is an invisible force field. Radiation comes from charged particles trapped inside that field. Jupiter’s magnetosphere traps many fast-moving particles, and those particles are what damages spacecraft — not the magnetism itself.
Why does Jupiter have a stronger magnetic field than Earth?
Jupiter is enormous, spins very fast (one day is less than 10 hours), and has a deep layer of liquid metallic hydrogen that conducts electricity. Moving electric currents inside that layer help create Jupiter’s powerful magnetic field. Earth’s liquid iron core does the same thing on a much smaller scale.
Can we see Jupiter’s magnetic field?
Not directly — magnetic fields are invisible. But we can see what Jupiter’s magnetic field does: bright auroras at both poles (visible in ultraviolet, infrared and visible light), and strong radio signals (which can even be picked up from Earth).
Could Jupiter’s magnetic field affect Earth?
No. Jupiter’s magnetic field, however enormous, is hundreds of millions of kilometres away. The Sun’s own magnetic field (the heliosphere) protects everything in the inner solar system. Earth’s weather, magnetism, and life are unaffected by Jupiter’s field.
Quick recap
- Jupiter has the strongest planetary magnetic field in the solar system — magnetic moment about 20,000× Earth’s
- It is generated by a deep ocean of liquid metallic hydrogen
- The magnetosphere around Jupiter is so big it would look bigger than the full Moon if our eyes could see magnetism — the largest planetary magnetosphere in the solar system
- The magnetotail can stretch almost to, or past, Saturn’s orbit depending on solar-wind conditions
- Discovered by NASA’s Pioneer 10 in December 1973
- Jupiter’s auroras are the most powerful planetary auroras in the solar system, partly fed by material from Io
- Ganymede is the only moon with its own intrinsic magnetic field, creating a tiny magnetosphere inside Jupiter’s
- Europa and Callisto show induced magnetic-field signals that may come from hidden salty oceans
Want to see Jupiter’s magnetic field in action? Visit the Juno mission page, Io (the volcanic feeder), Ganymede (the moon with its own field), or head back to the Jupiter pillar.