Journal article
Auroral Storm and Polar Arcs at Saturn—Final Cassini/UVIS Auroral Observations
Geophysical research letters, Vol.45(14), pp.6832-6842
07/24/2018
DOI: 10.1029/2018GL078094
Abstract
On 15 September 2017 the Cassini spacecraft plunged into Saturn's atmosphere after 13 years of successful exploration of the Saturnian system. The day before, the Ultraviolet Imaging Spectrograph (UVIS) on board Cassini observed Saturn's northern aurora for about 14 hr. During these observations, several auroral structures appeared, providing clues about processes simultaneously occurring in Saturn's magnetosphere. The observed dawn auroral enhancement together with the magnetic field and plasma wave data suggest that an intense flux closure process took place in the magnetotail. This enhanced magnetotail reconnection is likely caused by a magnetospheric compression induced by an interplanetary shock. Additionally, a polar arc is observed on the duskside, tracked for the first time from its growth until its quasi‐disappearance and used as an indicator of reconnection location on the dayside magnetopause. Observation of an atypical auroral arc at very high latitudes supports the interplanetary shock scenario.
Plain Language Summary
The plasma dynamics within Saturn's magnetosphere and the interactions of the plasma with the planetary magnetic field and the atmosphere are very complex. The magnetospheric dynamics can be investigated using the observations of the auroral emissions in the upper atmosphere of the polar regions of Saturn, since these polar lights are generated by precipitation into the atmosphere of electrons guided by the magnetic field lines. These electrons originating from various regions of the magnetosphere, the auroral emissions provide a global picture of the magnetospheric processes all around the planet. Here we use the final observations of Saturn's aurora by the Cassini spacecraft to understand the processes which occur in Saturn's magnetosphere on the day before the end of the Cassini mission in September 2017. In particular, a brightening and a broadening of one part of the aurora might be the response to a compression of the magnetosphere induced by an interplanetary shock in the solar wind. Additionally, an arc‐like auroral structure was tracked for the first time from its growth until its disappearance, revealing the mechanism producing it. Finally, the aurora exhibits another arc almost at the pole which had never been observed before.
Key Points
An intense auroral storm indicates the occurrence of magnetotail reconnection induced by an ICME
First observational evidence of the formation of a nightside polar arc
Most polar auroral arc ever observed at Saturn
Details
- Title: Subtitle
- Auroral Storm and Polar Arcs at Saturn—Final Cassini/UVIS Auroral Observations
- Creators
- B. Palmaerts - University of LiègeA. Radioti - University of LiègeD. Grodent - University of LiègeZ. H. Yao - University of LiègeT. J. Bradley - University of LeicesterE. Roussos - Max Planck Institute for Solar System ResearchL. Lamy - Observatoire de ParisE. J. Bunce - University of LeicesterS. W. H. Cowley - University of LeicesterN. Krupp - Max Planck Institute for Solar System ResearchW. S. Kurth - University of IowaJ.‐C. Gérard - Université de LiègeW. R. Pryor - Central Arizona College
- Resource Type
- Journal article
- Publication Details
- Geophysical research letters, Vol.45(14), pp.6832-6842
- DOI
- 10.1029/2018GL078094
- ISSN
- 0094-8276
- eISSN
- 1944-8007
- Number of pages
- 11
- Grant note
- NASA (1415150) Science and Technology Facilities Council (ST/N504117/1) STFC (ST/N000749/1)
- Language
- English
- Date published
- 07/24/2018
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984455363702771
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