Bader et al (GRL published Oct 2019).pdf (3.07 MB)
The Dynamics of Saturn's Main Aurorae
journal contributionposted on 2020-05-20, 14:41 authored by A Bader, SV Badman, SWH Cowley, ZH Yao, LC Ray, J Kinrade, EJ Bunce, G Provan, TJ Bradley, C Tao, GJ Hunt, WR Pryor
Saturn's main aurorae are thought to be generated by plasma flow shears associated with a gradient in angular plasma velocity in the outer magnetosphere. Dungey cycle convection across the polar cap, in combination with rotational flow, may maximize (minimize) this flow shear at dawn (dusk) under strong solar wind driving. Using imagery from Cassini's Ultraviolet Imaging Spectrograph, we surprisingly find no related asymmetry in auroral power but demonstrate that the previously observed “dawn arc” is a signature of quasiperiodic auroral plasma injections commencing near dawn, which seem to be transient signatures of magnetotail reconnection and not part of the static main aurorae. We conclude that direct Dungey cycle driving in Saturn's magnetosphere is small compared to internal driving under usual conditions. Saturn's large-scale auroral dynamics hence seem predominantly controlled by internal plasma loading, with plasma release in the magnetotail being triggered both internally through planetary period oscillation effects and externally through solar wind compressions.
All Cassini data are publicly available from the NASA Planetary Data System (https://pds.jpl.nasa.gov). PPO phase data (2004–2017) can be found on the University of Leicester Research Archive (http://hdl.handle.net/2381/42436). Cassini operations are supported by NASA (managed by the Jet Propulsion Laboratory) and European Space Agency (ESA). A. B. was funded by a Lancaster University FST studentship. S. V. B., L. C. R., and J. K. were supported by STFC Grant ST/R000816/1. S. V. B. was also supported by an STFC Ernest Rutherford FellowshipST/M005534/1. Z. Y. acknowledges financial support from the Belgian Federal Science Policy Office (BELSPO) via the PRODEX Programme of ESA. T. J. B. was supported by STFC Quota StudentshipST/N504117/1. G. J. H. was supported by STFC consolidated Grant ST/000692/2.
CitationBader, A., Badman, S. V., Cowley, S. W. H., Yao, Z. H., Ray, L. C., Kinrade, J., et al. ( 2019), The dynamics of Saturn's main aurorae. Geophysical Research Letters, 46, 10283– 10294. https://doi.org/10.1029/2019GL084620
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