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Periodic motion of Saturn's nightside plasma sheet

Periodic motion of Saturn's nightside plasma sheet
Periodic motion of Saturn's nightside plasma sheet

Saturn's magnetosphere is replete with magnetospheric periodicities; magnetic fields, plasma parameters, energetic particle fluxes, and radio emissions have all been observed to vary at a period close to that of Saturn's assumed sidereal rotation rate. In particular, periodicities in Saturn's magnetotail can be interpreted in terms of periodic vertical motion of Saturn's outer magnetospheric plasma sheet. The phase relationships between periodicities in different measurable quantities are a key piece of information in validating the various published models that attempt to relate periodicities in different quantities at different locations. It is important to empirically extract these phase relationships from the data in order to distinguish between these models, and to provide further data on which to base new conceptual models. In this paper a simple structural model of the flapping of Saturn's plasma sheet is developed and fitted to plasma densities in the outer magnetosphere, measured by the Cassini electron spectrometer. This model is used to establish the phase relationships between magnetic field periodicities in the cam region of the magnetosphere and the flapping of the plasma sheet. We find that the plasma sheet flaps in phase with Br and Bθ and in quadrature with the Bψ component in the core/cam region. The plasma sheet phase also has a strong local time asymmetry. These results support some conceptual periodicity models but are in apparent contradiction with others, suggesting that future work is required to either modify the models or study additional phase relationships that are important for these models.

2169-9380
Arridge, C.S.
2efb7acf-be5b-41b4-bade-8b4ff0d78236
André, N.
210d2676-9716-4567-bc3a-2f4dfdb34f9b
Khurana, K.K.
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Russell, C.T.
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Cowley, S.W.H.
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Provan, G.
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Andrews, D.J.
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Jackman, C.M.
9bc3456c-b254-48f1-ade0-912c5b8b4529
Coates, A.J.
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Sittler, E. C.
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Dougherty, M.K.
aa297043-7e86-4501-952b-a6363edaaba8
Young, D.T.
388d4bf2-84f9-4615-864d-f8d2be2b7fa0
Arridge, C.S.
2efb7acf-be5b-41b4-bade-8b4ff0d78236
André, N.
210d2676-9716-4567-bc3a-2f4dfdb34f9b
Khurana, K.K.
fdd7f0dc-99b0-4e66-a0e2-adbe022cc3dd
Russell, C.T.
0beb88bf-9d0e-4b75-80ae-61ba3776ce59
Cowley, S.W.H.
e8174910-ddcd-4a23-9d7c-0e1117def06c
Provan, G.
5de9f25e-ab6f-4c99-aeec-e45394a48a6b
Andrews, D.J.
b4685dd4-27ba-4cff-b2da-63fe439d0f2e
Jackman, C.M.
9bc3456c-b254-48f1-ade0-912c5b8b4529
Coates, A.J.
61022799-2e2b-46da-a964-23d9aaebe455
Sittler, E. C.
25061066-c935-4da0-beaf-01f6e9208446
Dougherty, M.K.
aa297043-7e86-4501-952b-a6363edaaba8
Young, D.T.
388d4bf2-84f9-4615-864d-f8d2be2b7fa0

Arridge, C.S., André, N., Khurana, K.K., Russell, C.T., Cowley, S.W.H., Provan, G., Andrews, D.J., Jackman, C.M., Coates, A.J., Sittler, E. C., Dougherty, M.K. and Young, D.T. (2011) Periodic motion of Saturn's nightside plasma sheet. Journal of Geophysical Research: Space Physics, 116 (11), [A11205]. (doi:10.1029/2011JA016827).

Record type: Article

Abstract

Saturn's magnetosphere is replete with magnetospheric periodicities; magnetic fields, plasma parameters, energetic particle fluxes, and radio emissions have all been observed to vary at a period close to that of Saturn's assumed sidereal rotation rate. In particular, periodicities in Saturn's magnetotail can be interpreted in terms of periodic vertical motion of Saturn's outer magnetospheric plasma sheet. The phase relationships between periodicities in different measurable quantities are a key piece of information in validating the various published models that attempt to relate periodicities in different quantities at different locations. It is important to empirically extract these phase relationships from the data in order to distinguish between these models, and to provide further data on which to base new conceptual models. In this paper a simple structural model of the flapping of Saturn's plasma sheet is developed and fitted to plasma densities in the outer magnetosphere, measured by the Cassini electron spectrometer. This model is used to establish the phase relationships between magnetic field periodicities in the cam region of the magnetosphere and the flapping of the plasma sheet. We find that the plasma sheet flaps in phase with Br and Bθ and in quadrature with the Bψ component in the core/cam region. The plasma sheet phase also has a strong local time asymmetry. These results support some conceptual periodicity models but are in apparent contradiction with others, suggesting that future work is required to either modify the models or study additional phase relationships that are important for these models.

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Published date: November 2011

Identifiers

Local EPrints ID: 437325
URI: http://eprints.soton.ac.uk/id/eprint/437325
ISSN: 2169-9380
PURE UUID: 94a28717-2db0-4049-9554-b0c3d709b561
ORCID for C.M. Jackman: ORCID iD orcid.org/0000-0003-0635-7361

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Date deposited: 24 Jan 2020 17:31
Last modified: 18 Feb 2021 17:23

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Contributors

Author: C.S. Arridge
Author: N. André
Author: K.K. Khurana
Author: C.T. Russell
Author: S.W.H. Cowley
Author: G. Provan
Author: D.J. Andrews
Author: C.M. Jackman ORCID iD
Author: A.J. Coates
Author: E. C. Sittler
Author: M.K. Dougherty
Author: D.T. Young

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