Saturn's Auroral Field-Aligned Currents: Observations from the Northern Hemisphere Dawn Sector During Cassini's Proximal Orbits
Abstract
We examine the azimuthal magnetic field signatures associated with Saturn's northern hemisphere auroral field‐aligned currents observed in the dawn sector during Cassini's Proximal orbits (April 2017 and September 2017). We compare these currents with observations of the auroral currents from near noon taken during the F‐ring orbits prior to the Proximal orbits. First, we show that the position of the main auroral upward current is displaced poleward between the two local times (LTs). This is consistent with the statistical position of the ultraviolet auroral oval for the same time interval. Second, we show the overall average ionospheric meridional current profile differs significantly on the equatorward boundary of the upward current with a swept‐forward configuration with respect to planetary rotation present at dawn. We separate the planetary period oscillation (PPO) currents from the PPO‐independent currents and show their positional relationship is maintained as the latitude of the current shifts in LT implying an intrinsic link between the two systems. Focusing on the individual upward current sheets pass‐by‐pass, we find that the main upward current at dawn is stronger compared to near noon. This results in the current density being ~1.4 times higher in the dawn sector. We determine a proxy for the precipitating electron power and show that the dawn PPO‐independent upward current electron power is ~1.9 times higher than at noon. These new observations of the dawn auroral region from the Proximal orbits may show evidence of an additional upward current at dawn likely associated with strong flows in the outer magnetosphere.
Additional Information
© 2020 The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited Received 28 NOV 2019; Accepted 31 MAR 2020; Accepted article online 14 APR 2020. Work at Imperial College was supported by UKRI/STFC grant ST/N000692/1 and ST/S000364/1. Work at the University of Leicester was supported by UKRI/STFC grant ST/N000749/1. E.J.B. was supported by a Royal Society Wolfson Research Merit Award. MKD was funded by Royal Society Research Professorship RP140004. HC was funded by the Cassini project through NASA Jet Propulsion Laboratory (JPL) contract 1579625. Calibrated magnetic field data from the Cassini mission are available from the NASA Planetary Data System (https://pds‐ppi.igpp.ucla.edu/search/?sc=Cassini&i=MAG). PPO phase data (2004–2017) are available from the University of Leicester Research Archive (http://hdl.handle.net/2381/42436).Attached Files
Published - 2019JA027683.pdf
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Additional details
- Eprint ID
- 102528
- Resolver ID
- CaltechAUTHORS:20200414-101248979
- ST/N000692/1
- Science and Technology Facilities Council (STFC)
- ST/S000364/1
- Science and Technology Facilities Council (STFC)
- ST/N000749/1
- Science and Technology Facilities Council (STFC)
- RP140004
- Royal Society
- 1579625
- JPL
- Created
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2020-04-14Created from EPrint's datestamp field
- Updated
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2021-11-16Created from EPrint's last_modified field