Stagnation of Saturn’s auroral emission at noon

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Title: Stagnation of Saturn’s auroral emission at noon
Authors: Radioti, A
Grodent, D
Gerard, JC
Southwood, DJ
Chane, E
Bonfond, B
Pryor, W
Item Type: Journal Article
Abstract: Auroral emissions serve as a powerful tool to investigate the magnetospheric processes at Saturn. Solar wind and internally driv en processes largely control Saturn’s auroral morphology. The main aur oral emission at Saturn is suggested to be connected with the magnetosphere - solar wind interaction, through the flow shear related to rotational dynamics. Dawn auroral enhancements are associated with intense field-aligned currents generated by hot tenuous plasma carried towards the planet in fast moving flux tubes as they return from tail reconnection site to the dayside. In this work we demonstrate, based on Cassini auroral observations, that the main auroral emission at Saturn, as it rotates from midnight to dusk via noon, occasionally stagnates near noon over a couple of hours. In half of the sequences examined, the auroral emission is blocked close to noon, while in three out of four cases, the blockage of the auroral emission is accompanied with signatures of dayside reconnection. We discuss some possible interpretations of the auroral ’blockage’ near noon. According to the first one it could be related to local time variations of the flow shear close to noon. Auroral local time variations are also suggested to be initiated by radial transport process. Alternatively, the auroral blockage at noon could be associated with a plasma circulation theory, according to which tenuously populated closed flux tubes as they return from the nightside to the morning sector experience a blockage in the equatorial plane and they cannot rotate beyond noon.
Issue Date: 7-Jun-2017
Date of Acceptance: 23-May-2017
URI: http://hdl.handle.net/10044/1/48685
DOI: https://dx.doi.org/10.1002/2016JA023820
ISSN: 2169-9402
Publisher: American Geophysical Union (AGU)
Start Page: 6078
End Page: 6087
Journal / Book Title: Journal of Geophysical Research: Space Physics
Volume: 122
Issue: 6
Copyright Statement: ©2017. American Geophysical Union. All Rights Reserved.
Sponsor/Funder: Science and Technology Facilities Council (STFC)
Science and Technology Facilities Council (STFC)
Funder's Grant Number: ST/K001051/1
ST/N000692/1
Keywords: Science & Technology
Physical Sciences
Astronomy & Astrophysics
Saturn
aurora
magnetosphere
giant planets
INTERPLANETARY MAGNETIC-FIELD
HUBBLE-SPACE-TELESCOPE
GIANT MAGNETOSPHERES
SOLAR-WIND
RECONNECTION
CIRCULATION
DYNAMICS
FLOWS
CUSP
FLUX
Publication Status: Published
Appears in Collections:Space and Atmospheric Physics
Physics
Faculty of Natural Sciences



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