Dynamic auroral storms on Saturn as observed by the Hubble Space Telescope

J D Nichols; S V Badman; K H Baines; R H Brown; E J Bunce; J T Clarke; S W H Cowley; F J Crary; M K Dougherty; J-C Gérard; A Grocott; D Grodent; W S Kurth; H Melin; D G Mitchell; W R Pryor; T S Stallard

doi:10.1002/2014GL060186

Dynamic auroral storms on Saturn as observed by the Hubble Space Telescope

Geophys Res Lett. 2014 May 28;41(10):3323-3330. doi: 10.1002/2014GL060186. Epub 2014 May 20.

Authors

J D Nichols¹, S V Badman², K H Baines³, R H Brown⁴, E J Bunce¹, J T Clarke⁵, S W H Cowley¹, F J Crary⁶, M K Dougherty⁷, J-C Gérard⁸, A Grocott², D Grodent⁸, W S Kurth⁹, H Melin¹, D G Mitchell¹⁰, W R Pryor¹¹, T S Stallard¹

Affiliations

¹ Department of Physics and Astronomy, University of Leicester Leicester, UK.
² Department of Physics and Astronomy, University of Leicester Leicester, UK ; Department of Physics, Lancaster University Lancaster, UK.
³ Space Science and Engineering Center, University of Wisconsin-Madison Madison, Wisconsin, USA.
⁴ Lunar and Planetary Lab, University of Arizona Tucson, Arizona, USA.
⁵ Center for Space Physics, Boston University Boston, Massachusetts, USA.
⁶ Laboratory for Atmospheric and Space Physics, University of Colorado Boulder Boulder, Colorado, USA.
⁷ Blackett Laboratory, Imperial College London London, UK.
⁸ Laboratoire de Physique Atmospherique et Planetaire, Universite de Liege Liege, Belgium.
⁹ Department of Physics and Astronomy, University of Iowa Iowa City, Iowa, USA.
¹⁰ Applied Physics Laboratory, Johns Hopkins University Laurel, Maryland, USA.
¹¹ Department of Science, Central Arizona College Coolidge, Arizona, USA.

Abstract

We present observations of significant dynamics within two UV auroral storms observed on Saturn using the Hubble Space Telescope in April/May 2013. Specifically, we discuss bursts of auroral emission observed at the poleward boundary of a solar wind-induced auroral storm, propagating at ∼330% rigid corotation from near ∼01 h LT toward ∼08 h LT. We suggest that these are indicative of ongoing, bursty reconnection of lobe flux in the magnetotail, providing strong evidence that Saturn's auroral storms are caused by large-scale flux closure. We also discuss the later evolution of a similar storm and show that the emission maps to the trailing region of an energetic neutral atom enhancement. We thus identify the auroral form with the upward field-aligned continuity currents flowing into the associated partial ring current.