Scientists have connected the dots between the Galilean moon and auroral emissions on Jupiter

(ORDO NEWS) — On November 8, 2020, NASA’s Juno spacecraft flew through an intense beam of electrons heading from Jupiter’s largest moon, Ganymede, to an auroral wake on the gas giant.

Scientists at the Southwestern Research Institute have used data from Juno to study the population of particles moving along the magnetic field line connecting Ganymede to Jupiter, while remotely sensing associated auroral ejecta to unravel the mysterious processes that create the flickering lights.

“Jupiter’s most massive moons create their own aurora at Jupiter’s north and south poles,” said Dr. Vincent Hugh, lead author of the paper outlining the study’s findings. “Each auroral trail, as we call them, is magnetically linked to its respective moon, like a magnetic leash connected to a glowing moon on Jupiter itself.”

Like Earth, Jupiter has auroral light around the polar regions as particles from its massive magnetosphere interact with molecules in Jupiter’s atmosphere.

However, Jupiter’s auroras are much more intense than Earth’s, and unlike Earth, Jupiter’s largest moons also create auroral spots. The Juno mission, led by Dr. Scott Bolton of SwRI, orbits Jupiter in a polar orbit and flew through the electron ‘thread’ connecting Ganymede to the corresponding auroral wake.

“Before Juno, we knew that these ejecta can be quite complex, ranging from a single auroral slick to multiple slicks, sometimes accompanied by an auroral veil, which we called a wake tail,” said Dr. Jamie Szalay, co-author at Princeton University. Juno, flying very close to Jupiter, showed that these auroral spots are even more complex than previously thought. ”

Ganymede is the only moon in our solar system that has its own magnetic field. Its mini-magnetosphere interacts with Jupiter’s massive magnetosphere, creating waves , accelerating electrons along the gas giant’s magnetic field lines, which can be directly measured by Juno.

Two instruments on Juno led by SwRI, the Jovian Auroral Distributions Experiment (JADE) and the Ultraviolet Spectrometer (UVS), provided key data for this study, which was also supported by Juno’s magnetic field sensor built at NASA’s Goddard Space Flight Center. .

“JADE measured electrons moving along magnetic field lines, and UVS imaged the corresponding auroral patch,” said Dr. Thomas Greathouse of SwRI, co-author of the study.

In this way, Juno can simultaneously measure the electron rain and immediately observe the ultraviolet light it creates when it hits Jupiter.

Previous Juno measurements have shown that large magnetic disturbances accompanied the electron beams causing the auroral wake. However, this time Juno did not observe such perturbations along with the electron beam.

“If our interpretation is correct, it confirms a decade-old theory that we created to explain auroral track morphology,” said Dr. Bertrand Bonfond, co-author of the study from the University of Li├Ęge in Belgium. The theory suggests that electrons accelerated in both directions create a multipoint dance of auroral wakes.”

“The relationship between Jupiter and Ganymede will be studied as part of the extended Juno mission, as well as the forthcoming JUICE mission of the European Space Agency,” Hugh said. “SwRI is building the next generation of UFS instruments for this mission.”

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