Bader et al On-line version (29 Oct 2018).pdf (8.7 MB)
Statistical Planetary Period Oscillation Signatures in Saturn's UV Auroral Intensity
journal contribution
posted on 2019-02-06, 11:44 authored by A Bader, SV Badman, J Kinrade, SWH Cowley, G Provan, WR PryorSaturn's auroral emissions are a good measure of field-aligned current (FAC) systems in the planet's magnetospheric environment. Previous studies based on magnetic field data have identified current systems rotating with the planetary period oscillations (PPOs) in both hemispheres, superimposed onto the local time-invariant current system producing the main auroral emission. In this study we analyze the statistical behavior of Saturn's ultraviolet auroral emissions over the full Cassini mission using all suitable Cassini-UVIS images acquired between 2007 and 2017. We examine auroral intensities by organizing the data by the two PPO coordinate systems. Strong statistical intensifications are observed close to the expected locations of upward FACs in both hemispheres, clearly supporting the main assumptions of the present theoretical model. We furthermore find clear signatures of modulation due to interhemispheric current closure from the PPO system in the opposite hemisphere, although with a weaker modulation amplitude. The auroral intensity in the northern hemisphere is shown to be modulated by a superposition of the FACs associated with both PPO systems, as the modulation phase and amplitude varies as expected for different relative orientations (beat phases) of the two PPO systems.
Funding
A. B. was funded by a Lancaster University FST studentship. J. K. and S. V. B. were supported by STFC grant ST/M001059/1. S. V. B. was also supported by an STFC Ernest Rutherford Fellowship ST/M005534/1. Work at the University of Leicester was supported by STFC Consolidated Grant ST/N000692/1. W. R. P. acknowledges support from the NASA JPL Cassini Project and Central Arizona College.
History
Citation
Journal of Geophysical Research: Space Physics, 2018, 123(10) pp. 8459-8472Author affiliation
/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and AstronomyVersion
- VoR (Version of Record)
Published in
Journal of Geophysical Research: Space PhysicsPublisher
American Geophysical Union (AGU), Wileyissn
2169-9380eissn
2169-9402Acceptance date
2018-09-26Copyright date
2018Available date
2019-02-06Publisher DOI
Publisher version
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018JA025855Notes
UVIS data are available from the NASA Planetary Data System (https://pds.jpl.nasa.gov). All PPO phase data (2004–2017) are available on the University of Leicester Research Archive (http://hdl.handle.net/2381/42436).Language
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