See Jupiter’s Northern Lights at the Height of a Solar Storm
Exploring the relationship between planets’ magnetospheres and solar winds could ultimately help identify habitable exoplanets.
Jupiter has its own version of the Northern Lights, and it can be hundreds of times more energetic than the earthly phenomenon.
For the first time, scientists have studied Jupiter's X-ray aurora during a solar storm. They found that it was eight times brighter than usual under these conditions, and that its brightest spot "pulsed" more quickly—every 26 minutes as opposed to 45 minutes. The researchers don't know exactly why this is, but ultimately understanding these kind of processes could help identify habitable planets elsewhere in the Universe.
Here, the image on the left shows the aurora as a coronal mass ejection (solar flare) reached Jupiter in October 2011; the image on the right shows it two days later when the solar wind had subsided. As the aurora is made of X-rays—which are more energetic than the light in our aurora borealis—they're not visible, but the brightness in the colouring is based on the data collected with NASA's Chandra observatory.
The study was published Tuesday in the Journal of Geophysical Research. William Dunn, a PhD student at University College London's Mullard Space Science Laboratory and lead author, explained in a phone call that this research will help demystify the relationship between Jupiter's massive magnetosphere (the area controlled by its magnetic field) and solar wind.
"We have a vague idea of what's going on between the Earth's magnetic field and the solar wind, but we don't really understand what happens elsewhere in the Solar System," he explained.
Jupiter is particularly interesting because its magnetic field and magnetosphere are very different from Earth's. For a start, Jupiter is much bigger than Earth (and every other planet combined) and its magnetic field is magnitudes stronger. It also spins faster with a full rotation every 10 hours, as opposed to 24 hours, and is affected by volcanic material from the moon Io.
Knowing more about how magnetospheres relate to solar winds could inform our search for potentially habitable exoplanets
As it's so different to Earth, it could help inform which processes connecting Earth to the solar wind are shared among other celestial objects, and which may be unique. "Because Jupiter presents a very different set of circumstances, Jupiter and Earth kind of provide us with two benchmarks against which we can understand all these other places and all these other features across the Universe," said Dunn.
One reason this is particularly cool: We think magnetic fields are crucial to support complex life. The fact that Mars's atmosphere was, we believe, stripped away by solar winds owing to its lack of a strong magnetic field, is a major reason many don't expect it to host life anywhere near its surface. Knowing more about how magnetospheres relate to the Sun and solar winds could therefore inform our search for potentially habitable exoplanets.
"By having a magnetic field, you get this protective boundary that prevents the solar wind sweeping away your atmosphere," said Dunn. "And so understanding the signatures that are associated with that protective boundary, and that interaction with the Sun, will help us to understand how well-protected the planet is from the solar wind."
For now, the researchers don't know exactly how the interplay between solar winds and Jupiter's magnetosphere works, but given the effect of the solar storm on the aurora, they know there is a relationship there.
Luckily for them, NASA's Juno orbiter is scheduled to reach Jupiter in July, and one of its goals is to specifically investigate the gas giant's magnetic field.