AsianScientist (Jun. 6, 2017) – Combined observations from three spacecraft show that Jupiter’s brightest auroral features recorded to date are powered by both the volcanic moon Io and interaction with the solar wind. These findings have been published in Geophysical Research Letters.
On Earth, auroras are clearly driven by the solar wind that streams past the planet. But Jupiter’s gigantic auroras—magnitudes more powerful than those on Earth—are believed to be mainly driven by factors within the Jovian system.
To get a better understanding of the forces that create Juptier’s auroras, an international team of researchers led by Dr. Tomoki Kimura at RIKEN Nishina Center for Accelerator-Based Science combined observations of Jupiter from three space-based sources: Japan’s Hisaki satellite, an earth-orbiting extreme ultraviolet observatory that was launched into low-earth orbit in 2013; the Juno spacecraft, which entered into orbit around Jupiter in July 2016; and the Hubble Space Telescope, which took high-resolution far ultraviolet photos of Jupiter as Juno entered into orbit
By combining the data from the three spacecraft—including snapshots taken by Hisaki at ten-minute intervals for a period of more than six months—the team was able to more precisely map out the movement of the sulfur gas emerging from powerful volcanoes on Jupiter’s moon, Io.
The found that sulfur gas from Io’s volcanoes is channeled into Jupiter’s polar region where it drives the auroras. These findings were detected during a “transient brightening” of Jupiter’s aurora that was detected in May 2016, as Juno was approaching. The data showed that the energy from Io’s gas emission was somehow transferred toward Jupiter at a speed approaching 400 to 800 kilometers per second in the equatorial region of the space around Jupiter.
“What is special about our observations,” said lead author Kimura, a Special Postdoctoral Researcher at RIKEN, “is that we were able to time the observations with the arrival of the Juno spacecraft into Jovian orbit. It turns out that Juno detected a shock wave originating from the solar wind, and this led us to infer that the solar wind was, along with Io, playing a role in the process by driving the energy toward Jupiter.”
In the past, it was generally considered that the magnetic field of a rotating astronomical body is powerful enough to completely dominate azimuthal movements of energy and mass near it, but the team’s findings challenge this assumption, as the energy seems to move from the area far from Jupiter toward Jupiter. Moreover, this process seems to hold for other rotating bodies such as neutron stars.
“The Jovian system is known to contain several icy moons—namely Europa and Ganymede—which may potentially have extraterrestrial life in their underground oceans of liquid water, and the energy driven from the far area toward Jupiter could provide support for chemical processes on the icy surface of the moons,” Kimura continued.
“In the past we did not know how the energy was accelerated to such tremendous velocities, but now, thanks to these findings, we have a better idea. Now that Juno is in orbit around Jupiter, we will continue to receive new observational data that will help us pin down how the energy is transferred, again allowing us to gain insights in our search for life in those icy worlds.”
The article can be found at: Kimura et al. (2017) Transient Brightening of Jupiter’s Aurora Observed by the Hisaki Satellite and Hubble Space Telescope During Approach Phase of the Juno Spacecraft.
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Source: RIKEN.
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