Auroras come in many shapes and sizes. Jupiter is known for its spectacular addition of bright northern lights, which also appear in the X-ray band. These northern lights are also extreme sources of energy that give off almost a gigawatt of energy in a few minutes. But what exactly causes it has been a mystery for the past 40 years. Now, a team has used data from a combination of satellites to find out what is causing these heavy emissions. The answer seems to be charged ions surfing on some kind of wave.
Ions have long been fingered as the cause of the aurora borealis, but it was not clear how exactly they got into the atmosphere. To find out, the researchers first had to find out where the ions came from. A clue was found in the position of the aurora itself.
Image of the northern lights on Jupiter as seen in the X-ray image in 2007 from Chandra, one of NASA’s X-ray telescopes.
Credit – X-Ray – NASA / CXC / SwRI / R. Gladstone et al .; Optical – NASA / ESA / Hubble Heritage (AURA / STScI)
Earthbound auroras usually occur between 65 and 80 degrees latitude, but do not exist above 80 degrees. At this point, the Earth’s magnetic field, which directs the ions into the atmosphere to create the polar lights, combines with the magnetic field created by the solar wind and carries the ions out to join the roaring sea of other passing particles.
Jupiter, on the other hand, regularly has auroras that appear beyond this 80 degree line, and the aurora borealis may appear differently at the north and south poles, while they would be similar on Earth. All of this suggests the idea of a “closed” magnetic field, which means that the magnetic field of one planet emanates from one point and hits the planet again at another, without ever being tied to the magnetic field caused by the solar wind.
Dr. Becky explains Jupiter’s now solved Aurora puzzle.
Credit – Dr. Becky YouTube channel
To test this new theory about the arrangement of Jupiter’s magnetic field, Dr. Zhonghua Yao of the Chinese Academy of Sciences in Beijing different aspects of Jupiter’s magnetic field. The result, which most closely matched the varying, pulsating aurora borealis in observations, was a closed magnetic system in which the gas giant’s magnetic field began at a pole, extended for millions of miles into empty space, and then returned to the planet.
With this improved understanding of Jupiter’s magnetic field theory, it was time to take some measurements. Fortunately, two tools were in close proximity – the XMM-Newton, a near-earth X-ray observatory, and Juno, which recently released a spectacular video showing details of one of its flybys over the Jupiter system.
X-rays aren’t the only type of aurora on Jupiter. Here are some ultraviolet aurora images of Jupiter from the Juno Ultraviolet Spectrograph instrument. The images contain intensities from three spectral ranges, false color red, green and blue, which provide qualitative information about precipitating electron energies (respectively high, medium and low).
Photo credit: NASA / SwRI / Randy Gladstone
In 2017, XMM-Newton aimed his optics at Jupiter for a full 26 hours and saw an X-ray aurora pulse every 27 minutes. At the same time, Juno was flying past just above the planet’s surface, collecting magnetometric data. When the two sets of data were compared, it became clear that the northern lights were caused by changes in Jupiter’s magnetic fields.
These fluctuations seem to come from some kind of “wave” that exists in the field itself. Technically known as Electromagnetic Ion Cyclotron (EMIC) waves, they are created when the magnetic field itself is compressed by the solar wind hitting it. Heated particles that are compressed in the magnetic field are then forced into a wave pattern, where they follow the magnetic field lines to the poles, where they rejoin the atmosphere and then create the polar lights.
UT video about upcoming missions to Jupiter.
Researchers led by Dr. William Dunn from University College London were able to use the two data sets to follow the wave formation up to the Aurora process. And they think the same system could exist with other gas giants. The ion type could be different (Saturn has water ions from Enceladus versus Jupiter which is feeding sulfur from Io) but the process would be almost the same. It could even take place on exoplanets.
These data, which are already 4 years old, will not be the last on this subject. ESA has a mission called Jupiter Icy Moons Explorer (Juice) that will reach the largest planet in the solar system in 2029. With a little luck we will get even more spectacular pictures and more information about these breathtaking, otherworldly northern lights.
ESA – The mystery of the causes of Jupiter’s X-ray aurors has been solved |
Advances in Science – Uncover the source of Jupiter’s X-ray auroral eruptions
Physics World – Vibrations drive X-rays in Jupiter’s northern lights
CBS – Astronomers finally reveal the 40-year-old mystery of Jupiter’s epic X-ray aurora flares
JPL – 40-year mystery solved: source of Jupiter’s X-rays uncovered
Image showing a representation of Jupiter’s ions moving on a closed magnetic field loop, creating the X-ray aurors on the planet.
Credit – Yao / Dunn / ESA / NASA