A new study published in the scientific journal Nature (1), in which Bertrand Bonfond, a researcher at the STAR Research Unit at ULiège, has questioned the mechanisms responsible for auroral emissions on Jupiter. The Jovian aurorae, more powerful than the terrestrial aurorae, are, contrary to what was thought, essentially derived from turbulent processes.
Since its launch in orbit around Jupiter in July 2016, the Juno probe (NASA) has already delivered many unseen data to the international group of researchers who supervise the mission. Bertrand Bonfond, a post-doc researcher at the Laboratory of Atmospheric and Planetary Physics (STAR Research Institute) and his colleagues at ULiège, are particularly interested in the polar aurora observed on the largest planet of our solar system.
Aurorae are the result of the impact of energetic particles coming from the neighborhood of a planet in the atmosphere of this planet. These electrically charged particles are guided by the magnetic field of the planet and hit the atmosphere at the poles, hence the term polar auroras. On Earth, there are two families of processes that accelerate the particles, steady processes, involved in the brightest auroras and turbulent processes, associated with variable emissions and less brilliant. "The Juno probe isperfect to study the aurora, since you can directly measure particles accelerated towards the planet and take pictures of the region where they impact the atmosphere thanks to the UV camera, named Juno-UVS, that was partially designed in Liège. "
Jupiter's auroral emissions are much more powerful and brilliant than those of the Earth and the international team of researchers was convinced that they could only be generated by processes similar to the ones causing the brightest aurora at Earth: steady processes. However, the new observations made by the Juno probe suggest that this is not the case. The Jovian auroras are in fact essentially governed by turbulent processes.
"With Juno we were looking for steady processes signatures and we indeed found a few. But even in these places, it is the turbulent processes that dominate, "emphasizes Bertrand Bonfond. These results provide an insight into how different planets interact electromagnetically with their spatial environments. With this discovery, we now know that the polar auroras present on two planets of the same system can be formed in completely different ways. The next step will be to understand how these turbulent processes work on Jupiter. The Juno mission, which is scheduled to end around 2021, may well bring new surprises in the coming months and years.
For more than 25 years, the study of the jovian polar auroras has been one of the specialties of the researchers of the Laboratory of Planetary and Atmospheric Physics (LPAP), now a member of the Space Science, Research and Astrophysics Research Institute (STAR) of the University of Liège. Much of this research was funded by the Federal Science Policy Public Service program (BelSPO) through the ESA-PRODEX program
Artist's view of the northern lights of Jupiter seen by the Juno spacecraft. The polar auroras represented here in blue, are actually observed in the ultraviolet and are therefore invisible to the naked eye. The shape of the aurora was reconstructed from observations made on 11 December 2016 by the Juno-UVS instrument. The map of Jupiter's surface comes from observations acquired in 2015 by the Hubble Space Telescope. (Https://svs.gsfc.nasa.gov/12021).
Publication Nature
(1) Mauk et al., Discrete and broadband electron acceleration in Jupiter's powerful aurora, Nature, 23648, 6 september 2017. http://dx.doi.org/10.1038/nature23648
More informations
- The ULiège analyzes the magnetosphere and auroras of Jupiter (Press release)
- Highlighting the auroras of Jupiter (Popular article)
- Laboratory of Atmospheric and Planetary Physics (LPAP ULg)
- Space Science, Technology and Astrophysics Research (STAR Institute, ULg)
Laboratoire de Physique Atmosphérique et Planétaire (LPAP), Unité de Recherche STAR, Université de Liège
Dr Bertrand Bonfond, b.bonfond@uliege.be
