Jupiter displays a bright aurora in its high latitudes, similar, but not identical, to the phenomenon on Earth. Solar winds light Earth’s aurora by slamming particles against the magnetic field, whereas on Jupiter the aurora forms as the electric field in the magnetosphere pushes electrons upward and ions downward.
The behavior of different molecules in Jupiter’s magnetic field creates auroral activity in different parts of the electromagnetic spectrum. In the ultraviolet range—wavelengths shorter than visible light but longer than X-ray waves—the aurora appears as the hydrogen isotopes H and H2 shed electrons. An aurora also appears in the infrared range where wavelengths are longer than those visible to the human eye, the result of excited hydrogen ion H3+ molecules.
In recent years, images from the Hubble Space Telescope and Juno spacecraft have highlighted the ultraviolet aurora crowning Jupiter, and now similar scenes are available for the infrared aurora. Using the Infrared Camera and Spectrograph (IRCS) instrument on the Subaru telescope atop Hawaii’s Mauna Kea summit, Watanabe et al. have created the first movie of Jupiter’s infrared aurora.
The researchers analyzed approximately 1 hour of data at 45- to 110-second intervals from 25 May 2016 that focused on Jupiter’s northern polar region. With a boost from adaptive optics, a sophisticated technique that corrects image distortions caused by Earth’s atmosphere, the authors produced a high-resolution movie of the infrared aurora.
The movie revealed a pulsating patch of infrared aurora that flashed about every 10 minutes. This cycle had not been previously identified in the infrared, although other studies recognized a similar pulsation in the ultraviolet range. The authors developed a model to investigate the pulse. The model suggested that electrons entering Jupiter’s atmosphere may drive the pulsation, but the authors note that more research is needed to uncover the mechanisms behind the pulse.
The movie of Jupiter’s infrared aurora and the pulsation cycle it revealed provide valuable insights into the dynamics of the planet’s magnetosphere. The upcoming observations from the orbiting Juno spacecraft could shed further light on the results presented in this study. (Geophysical Research Letters, https://doi.org/10.1029/2018GL079411, 2018)
—Aaron Sidder, Freelance Writer