Webb Telescope Captures Jupiter’s “Fizzing” Auroras, Revealing Unexpected Light Show

Jupiter’s northern lights are putting on a more dynamic and puzzling light show than scientists ever expected. New observations from the James Webb Space Telescope (JWST) reveal that the gas giant’s auroras can flicker and change within seconds, challenging previous understandings of how these massive light displays behave.

The findings, published May 12 in Nature Communications, compare simultaneous infrared and ultraviolet observations of Jupiter’s auroras, offering unprecedented insight into the planet’s upper atmosphere and magnetic field.

“What a Christmas present it was – it just blew me away!” said Jonathan Nichols from the University of Leicester, who led the research team. “We wanted to see how quickly the auroras change, expecting it to fade in and out ponderously, perhaps over a quarter of an hour or so. Instead we observed the whole auroral region fizzing and popping with light, sometimes varying by the second.”

Tracking the Flickering Lights

Using Webb’s Near-Infrared Camera, researchers captured images of Jupiter’s northern auroral emissions on December 25, 2023, with unprecedented 3-second time resolution – approximately 100 times faster than typical ground-based observations.

The study focused on emissions from trihydrogen ion (H3+), which plays a key role in Jupiter’s atmospheric energy balance. These ions form when energetic particles accelerated in Jupiter’s magnetosphere collide with molecules in the upper atmosphere.

The research team estimated that H3+ has a surprisingly short lifetime of just 150 seconds in Jupiter’s aurora – far briefer than previous estimates of 10-15 minutes. This shorter lifetime means the aurora can respond much more rapidly to changes in Jupiter’s magnetosphere than previously thought.

Perplexing Brightness Patterns

The observations revealed several unexpected features, including a bright “dusk active region” (DAR) that glows intensely in infrared light but has little counterpart in ultraviolet observations.

“Bizarrely, the brightest light observed by Webb had no real counterpart in Hubble’s pictures,” Nichols noted. “This has left us scratching our heads. In order to cause the combination of brightness seen by both Webb and Hubble, we need to have an apparently impossible combination of high quantities of very low energy particles hitting the atmosphere – like a tempest of drizzle! We still don’t understand how this happens.”

The simultaneous observations from Webb and Hubble revealed that while some auroral features appear in both wavelengths, others are unique to either infrared or ultraviolet light.

Fast-Moving Pulses

The team also discovered rapid eastward-traveling auroral pulses (REAPs) – waves of light that move at approximately 60 km per second, or about 20 times Jupiter’s rotation rate. These pulses have a period of about 1.6 minutes and may be connected to electromagnetic waves in Jupiter’s magnetosphere.

Similar rapid pulsations were observed propagating along the “tail” of aurora connected to Jupiter’s moon Io, traveling at speeds of about 67 km per second.

Implications for Planetary Heating

The findings have significant implications for understanding how Jupiter’s upper atmosphere is heated – a long-standing question in planetary science.

The researchers found that H3+ radiates only about 2% of the thermal energy deposited by electron precipitation during auroral flares, making it a less effective “thermostat” for Jupiter’s upper atmosphere than previously believed.

In some regions, like the dusk active region, H3+ radiation exceeded the local heating rate, while in others it fell far short – suggesting complex energy balance mechanisms at work across Jupiter’s polar regions.

Future Research

These observations open new avenues for understanding Jupiter’s complex space environment and may provide context for the European Space Agency’s Jupiter Icy Moons Explorer (Juice) mission, which is currently en route to the giant planet.

The research team plans to conduct additional Webb observations and compare them with data from NASA’s Juno spacecraft, which has been orbiting Jupiter since 2016, to better understand the causes of these enigmatic auroral features.

By mapping the detailed behavior of Jupiter’s aurora, scientists hope to gain insight into the interactions between the planet’s magnetic field, atmosphere, and moons – knowledge that could improve our understanding of magnetic fields and atmospheres throughout the universe.