Scientists solve 40-year mystery of Jupiter’s aurora X


A research team co-led by UCL (University College London) has solved a decades-old mystery about how Jupiter produces a spectacular burst of X-rays every few minutes.

X-rays are part of Jupiter’s auroras – bursts of visible and invisible light that occur when charged particles interact with the planet’s atmosphere. A similar phenomenon occurs on Earth, creating the Northern Lights, but Jupiter’s is much more powerful, releasing hundreds of gigawatts of energy, enough to briefly power all of human civilization *.

In a new study published in Scientists progress, the researchers combined close-up observations of Jupiter’s environment from NASA’s Juno satellite, which currently orbits the planet, with simultaneous x-ray measurements from the European Space Agency’s XMM-Newton observatory (which is in Earth’s own orbit).

The research team, led by UCL and the Chinese Academy of Sciences, found that X-ray flares were triggered by periodic vibrations of Jupiter’s magnetic field lines. These vibrations create waves of plasma (ionized gas) that send heavy ion particles to “surf” along magnetic field lines until they shatter into the planet’s atmosphere, releasing energy in the form of x-rays.

Co-lead author Dr William Dunn (UCL Mullard Space Science Laboratory) said: “We saw Jupiter produce X-rays for four decades, but we didn’t know how it happened. We only knew they were produced when ions crashed into the planet’s atmosphere.

“Now we know that these ions are carried by plasma waves – an explanation that has not been offered before, although a similar process produces Earth’s own aurora. So it could be a universal phenomenon. , present in many different environments in space. ”

X-ray auroras occur at the north and south poles of Jupiter, often with clockwork regularity – during this observation, Jupiter produced bursts of X-rays every 27 minutes.

The charged ion particles hitting the atmosphere come from volcanic gas flowing into space from giant volcanoes on Jupiter’s moon, Io.

This gas ionizes (its atoms are stripped of electrons) due to collisions in Jupiter’s immediate environment, forming a plasma donut that surrounds the planet.

Co-lead author Dr Zhonghua Yao (Chinese Academy of Sciences, Beijing) said, “Now that we have identified this fundamental process, there are plenty of possibilities to study it next. Similar processes probably occur around Saturn, Uranus, Neptune. and probably exoplanets as well, with different types of charged particles “surfing” the waves. ”

Co-author Professor Graziella Branduardi-Raymont (UCL Mullard Space Science Laboratory) said: “X-rays are typically produced by extremely powerful and violent phenomena such as black holes and neutron stars, so it looks strange. that simple planets also produce them.

“We can never visit black holes, because they are beyond space travel, but Jupiter is on our doorstep. With the arrival of the Juno satellite in Jupiter’s orbit, astronomers now have a fantastic opportunity to closely study an environment that produces x-rays. ”

For the new study, the researchers analyzed observations of Jupiter and its surrounding environment made continuously over a 26-hour period by the Juno and XMM-Newton satellites.

They found a clear correlation between the waves in the plasma detected by Juno and the X-ray auroral flares at Jupiter’s north pole recorded by X-MM Newton. They then used computer modeling to confirm that the waves would drag the heavy particles towards Jupiter’s atmosphere.

It is not clear why the magnetic field lines periodically vibrate, but the vibration may result from interactions with the solar wind or from high-speed plasma flow in Jupiter’s magnetosphere.

Jupiter’s magnetic field is extremely strong – about 20,000 times stronger than that of Earth – and therefore its magnetosphere, the area controlled by this magnetic field, is extremely large. If it were visible in the night sky, it would cover an area several times the size of our moon.

The work was supported by the Chinese Academy of Sciences, the National Foundation of Natural Sciences of China and the UK Science and Technology Facilities Council (STFC), the Royal Society and the Natural Environment Research Council, as well as the ESA and NASA.

* Jupiter’s x-ray aurora alone releases about a gigawatt, equivalent to what a power plant could produce over a period of days.


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