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Seasonal structures in Saturn's dusty Roche Division correspond to periodicities of the planet's magnetosphere

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posted on 30.04.2019, 14:27 by RO Chancia, MM Hedman, SWH Cowley, G Provan, S-Y Ye
We identify multiple periodic dusty structures in Saturn’s Roche Division, a faint region spanning the∼3000 km between the A and F rings. The locations and extent of these features vary over Cassini’s tour of the Saturn system, being visible in 2006 and 2016-2017, but not in 2012-2014. These changes can be correlated with variations in Saturn’s magnetospheric periods. In 2006 and 2016-2017, one of the drifting magnetospheric periods would produce a 3:4 resonance within the Roche Division, but in 2012-2014 these resonances would move into the A ring as the magnetospheric periods converged. A simple model of magnetic perturbations indicates that the magnetic field oscillations responsible for these structures have amplitudes of a few nanotesla, comparable to the magnetic field oscillation amplitudes of planetary period oscillations measured by the magnetometer on board Cassini. However, some previously unnoticed features at higher radii have expected pattern speeds that are much slower than the magnetospheric periodicities. These structures may reflect an unexpectedly long-range propagation of resonant perturbations within dusty rings.

Funding

This work was supported by NASA through the Cassini Data Analysis Program NNX15AQ67G. Work at the University of Leicester was supported by STFC Consolidated Grant ST/N000749/1. We thank Georg Fischer for helpful comments on an earlier version of this manuscript. We are grateful for helpful conversations with Douglas P. Hamilton concerning Lorentz resonances and quantifying their strengths. We also thank the Cassini project and imaging team for acquiring the data for this work.

History

Citation

Icarus, 2019

Author affiliation

/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and Astronomy

Version

AM (Accepted Manuscript)

Published in

Icarus

Publisher

Elsevier for Academic Press

issn

0019-1035

Acceptance date

12/04/2019

Copyright date

2019

Available date

30/04/2019

Publisher version

https://www.sciencedirect.com/science/article/pii/S0019103518307978?via=ihub

Language

en

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