Jupiter's mysterious hotspot created by solar wind: study
By science reporter Jacinta Bowler
ABC Science
Topic:Planets and Asteroids
28m ago28 minutes agoThu 3 Apr 2025 at 7:00pm
Aurora at Jupiter's north pole.
The solar wind may play a greater role in boosting Jupiter's auroras than scientists had previously thought. (Supplied: NASA, ESA, J. Nichols (University of Leicester) A. Simon NASA and OPAL team.)
In short:
A high temperature band the size of multiple Earths has been captured on Jupiter for the first time.
Scientists believe the heat was due to solar winds squeezing the magnetic field, and this may happen multiple times a month.
What's next?
This phenomenon may also occur on the southern hemisphere of Jupiter, and more research can determine how much influence the solar wind has on the planet's weather.
Jupiter's stunning auroras have been captured by many telescopes and spacecraft since Voyager 1 flew by nearly 50 years ago.
Recently, scientists detected a mysterious band of hot gas — almost hot enough to melt aluminium — that stretched halfway around the planet.
The band of gas was hundreds of degrees warmer than it's surroundings, said James O'Donoghue, a planetary scientist at the University of Reading.
"It's the first time we've ever seen anything like this on a giant planet,"
he said.
It was unknown what caused the hotspot, but a new analysis of data from NASA's Juno spacecraft by Dr O'Donoghue and colleagues may hold the answer.
Their research suggests Jupiter was hit by a massive wave of particles from the Sun slamming into the planet's magnetic shield.
This in turn produced an intense auroral burst that sent temperatures soaring.
A map of jupiter showing a wide band of hotter temperatures.
The heat map of Jupiter showed a large band of gas over 500 degrees Celsius. (Supplied: Dr James O’Donoghue, University of Reading)
The research, published today in Geophysical Research Letters, may up-end scientists' understanding of how particles from the Sun — aka "solar wind" — boost auroras on Jupiter and other planets.
"The outer planets [like Jupiter] have their own auroras which have long been thought to be highly internally-driven," Dr O'Donoghue said.
"But what we're increasingly finding is that the solar wind can have a massive effect on boosting auroral activity."
A mysterious hot spot
In late January 2017, the Keck Telescope in Hawaii pointed its sights towards Jupiter, like it has many times before, and found something unusual.
Using a measurement of a type of hydrogen, the telescope captured a large band of heat which wasn't supposed to be there.
While the background temperature of Jupiter is usually around 350 degrees Celsius, the band of heated gas was more than 500 degrees.
"Using one of the largest telescopes on Earth, we found a vast, planetary-scale region of unexpectedly high temperatures in Jupiter's upper atmosphere," Dr O'Donoghue said.
"This heat is located far from the polar auroras, where we usually expect high temperatures."
Auroras throughout the solar system are produced by charged particles interacting with the magnetosphere — a planet-wide shield many planets have — and the upper atmosphere, which can cause a surprisingly large increase in heat.
"Heavily used electric cables get warm to the touch because a current runs through them, and the upper atmosphere of a planet does the same," Dr O'Donoghue said.
Earth's auroras are caused by the Sun's solar winds streaming charged particles down on Earth's magnetosphere that travel towards the poles where they excite different gases in the atmosphere.
But it was thought the permanent auroras on the outer planets like Jupiter, Saturn, Uranus and Neptune weren't affected by the Sun.
In Jupiter's case, the aurora is partially caused by oxygen and sulphur particles spewing out from giant volcanoes on its nearby moon, Io, which then interact with Jupiter's magnetic field.
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In 2021, Dr O'Donoghue and his team published a study that suggested auroras could be the cause of this band of heat away from the poles, but they didn't have the full picture.
"The 2017 observations had shown that Jupiter's auroras could heat the planet, but the cause of this specific hot feature was unclear" he said.
"We needed more evidence to confidently confirm it could be due to the solar wind."
A lucky spacecraft
On the same day as the Keck observation, NASA's Juno spacecraft just happened to be undertaking its fourth flyby of the gas giant, coming within 5,000 kilometres of Jupiter's clouds on the northern hemisphere of the planet.
Data captured by Juno revealed Jupiter's magnetosphere was being compressed when the spacecraft went through it.
Side by side images of solar flare
The Sun's solar flares, like these ones from May 2024, are linked to outbursts of solar wind. (Supplied: NASA/SDO)
"By combining new data from NASA's Juno mission, new solar wind modelling, and new methods to measure the feature's speed, we found that a major solar wind event occurred just hours earlier, making it the likely trigger," Dr O'Donoghue said.
The idea is that when the solar winds slammed into Jupiter they squashed the magnetic field, which produced extreme auroral activity and heat at the poles.
According to Dr O'Donoghue, superheated gas spilled south towards the equator "like a giant wave".
According to Lucyna Kedziora-Chudczer, an astronomer at the University of Southern Queensland and expert in Jupiter's aurora, the solar wind explanation is the best currently available.
"This paper is a great example of showing how observation from the ground can complement observations from space," she said.
"It's quite exciting because this is the first time it's been seen."
A beautiful picture of Jupiter, with swirling clouds and the red spot at the top of the image.
Juno has undertaken dozens of flybys of Jupiter, and is still active years after its planned retirement. (NASA: JPL-Caltech/SwRI/MSSS/Gerald Eichstad/Sean Doran/CC NC SA)
The researchers believe this phenomenon could occur multiple times a month, and suggest there might be plenty more opportunities to catch it using Earth-based telescopes.
"So far, we've only seen this feature in Jupiter's northern hemisphere — but there should be a southern counterpart: a similar wave of heating moving away from the southern aurora," Dr O'Donoghue said.
"Future work will focus on tracking down more of these events in both hemispheres and measuring how fast they travel.
"This will help us to map Jupiter's global wind circulation and understand just how much influence the solar wind has on upper-atmospheric weather."
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Posted28m ago28 minutes agoThu 3 Apr 2025 at 7:00pm
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