University of Minnesota-led team helps explain what powers Jupiter’s brightest auroras

MINNEAPOLIS/ST. PAUL (09/17/2026) — When NASA’s Juno spacecraft first flew over Jupiter’s poles in 2016, it found something scientists could not explain: The electrons powering the planet’s auroras were predominantly accelerating in a very different way than those above Earth.

A University of Minnesota Twin Cities-led research team has now identified a process that helps explain what Juno observed. In a study published in Science Advances, the researchers found that Jupiter’s auroral region can generate powerful plasma waves known as Alfvén waves. These waves accelerate electrons toward the planet’s atmosphere, producing the brightest auroras in the solar system.

Auroras form when charged particles, primarily electrons, accelerate along a planet’s magnetic field lines and collide with its upper atmosphere. Jupiter’s auroras are hundreds of times more powerful than Earth’s.

The findings also help explain why Jupiter’s upper atmosphere is much hotter than expected. Its temperature has been measured at approximately 700 kelvin, or 800 degrees Fahrenheit. Sunlight alone would warm the atmosphere to only about 150 kelvin, or -190 degrees Fahrenheit. Auroral heating helps close that gap, making an understanding of how the auroras are powered essential to explaining temperatures on Jupiter and other giant planets.

Before Juno, scientists expected Jupiter’s auroras to behave like scaled-up versions of Earth’s. A steady voltage along the planet’s magnetic field lines would accelerate electrons toward the atmosphere, giving nearly all of them approximately the same amount of energy. Instead, Juno found that most of the electrons above Jupiter’s auroras arrive with a broad range of energies. That pattern could not be explained by a steady voltage alone. It suggested that waves also play an important role in accelerating the electrons.

The waves, known as Alfvén waves, travel along magnetic field lines. Much like a plucked string sends a vibration along its length, a disturbance in a magnetic field line can send a wave through space. Under the right conditions, an Alfvén wave develops an electric field that accelerates electrons toward the atmosphere.

Scientists have long thought these waves formed roughly a million miles away, near Jupiter’s equator, and traveled toward its poles. The new study shows that Jupiter’s auroral region can also generate Alfvén waves locally, close to where the electron acceleration occurs.

Using Juno’s measurements and plasma simulations, the researchers identified a three-step process:

• A beam forms. A steady voltage accelerates electrons along Jupiter’s magnetic field lines, concentrating them into a beam with similar energies.
• The beam generates waves. Once the electrons reach approximately 77 percent of the speed of light, the beam becomes unstable and produces Alfvén waves.
• The waves accelerate more electrons. The locally generated waves transfer energy to surrounding electrons, accelerating them across a broad range of energies. This produces the pattern Juno has repeatedly observed and some of the most intense electron energy fluxes ever measured above Jupiter’s auroras.
  
  

“For decades, the upper atmosphere of Jupiter had been treated as a passive region where electromagnetic energy gets dissipated,” said lead author Ali Sulaiman, an assistant professor in the University of Minnesota School of Physics and Astronomy. “It turns out it is an active region that generates waves that participate in the auroral process, changing how physicists account for global energy flow around giant planets.”

Rather than simply receiving energy generated elsewhere in Jupiter’s magnetic environment, the auroral region helps produce the waves that power its own activity.

The study was led by researchers at the University of Minnesota Twin Cities in collaboration with the Johns Hopkins Applied Physics Laboratory, Princeton University, University of Alaska Fairbanks, the University of Iowa and the Southwest Research Institute. The work was supported by NASA.

Read the full study, “Jupiter’s brightest auroras are powered by locally generated Alfvén waves,” in Science Advances.