Researchers have uncovered a new clue to the mysteries of Jupiter’s auroras with help from NASA’s Juno spacecraft, with the detection of a previously unknown plasma wave mode above the gas giant’s north pole.
Just as on Earth, alien worlds experience auroras. Now, University of Minnesota Twin Cities astronomers and colleagues from other institutions have identified a novel plasma mode in Jupiter’s aurora, providing new insights into the relationship between magnetic fields and plasmas in extraterrestrial environments.
Researchers from the University of Iowa and the Southwest Research Institute joined the Twin Cities team in exploring the strange plasma behavior occurring at Jupiter’s northernmost extremes. The team utilized data collected by NASA’s Juno spacecraft as it passed over Jupiter’s north pole on an extremely tight orbit, providing an exceptional view of the region that surpassed even the data collected by the James Webb Space Telescope.
Auroral Explorations
“The James Webb Space Telescope has given us some infrared images of the aurora, but Juno is the first spacecraft in a polar orbit around Jupiter,” said co-author Ali Sulaiman, an assistant professor in the University of Minnesota School of Physics and Astronomy.
Plasma, a state of matter where extreme heat breaks atoms down into electrons and ions, fills the space around magnetized planets such as Jupiter. When those tiny particles, which once were atoms, accelerate towards their planet’s atmosphere, the gases residing high above the surface light up on contact.
While on Earth, such events produce brilliant blue and green displays that are considered visually striking; Jupiter’s aurora, however, is quite different. Jovian auroras shine in the ultraviolet and infrared spectrums, invisible to the naked eye, yet observable with the proper instruments, such as those aboard Juno.
New Plasma Waves on Jupiter
The researchers identified unique conditions on Jupiter that result in the very different auroras from those on Earth. Jovian polar plasma exists at a very low density, while its magnetic field is extremely strong. This combination generates plasma waves at a much lower frequency than on Earth, resulting in a distinctly different type of aurora, characterized by a new wave mode that begins as an Alfvén wave at a small wave number before transitioning to a Langmuir wave at a large wave number.
Due to their usual resonance cone structure, the waves can produce a saucer-like feature whenever a spacecraft passes over a localized source, never before seen in the Alfvén-Langmuir mode. The researchers suggest that the polar regions of other highly magnetized giant planets may feature similar conditions.
“While plasma can behave like a fluid, it is also influenced by its own magnetic fields and external fields,” said lead author Robert Lysak, a professor in the University of Minnesota School of Physics and Astronomy and a plasma dynamics expert.
Another difference between he two planets’ auroras can be found in their differing shapes. On Earth, auroras form in a donut shape around the polar caps, yet on Jupiter, the complex magnetic field pushes particles to flood directly into the polar cap itself.
The Juno Spacecraft
After launching in 2011, Juno trekked across our solar system for five years before finally reaching Jupiter in 2016. The solar-powered spacecraft has been observing the planet since completing its initial mission in 2021. Since then, Juno’s lifespan has been extended with its present mission scheduled through September of 2025, providing a continual stream of in-depth data on Jupiter.
As the Juno spacecraft continues its mission to study Jupiter, the team hopes to receive further data for their study of the planet’s unusual auroras. Beyond the immediate interest in Jupiter’s previously unseen conditions, only further observation across many distant gas giants will be able to confirm if the Jovian polar situation is unique or common to many similar exoplanets.
The paper, “New Plasma Regime in Jupiter’s Auroral Zones,” appeared in Physical Review Letters on July 16, 2025.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.