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Dual periodicities in planetary-period magnetic field oscillations in Saturn's tail

Dual periodicities in planetary-period magnetic field oscillations in Saturn's tail
Dual periodicities in planetary-period magnetic field oscillations in Saturn's tail

We examine magnetic field data from 10 apoapsis passes of the Cassini spacecraft during 2006 when the spacecraft explored the midnight and dawn sectors of Saturn's magnetotail to down-tail distances of ∼65 RS (Saturn radius, RS, is 60,268 km). Oscillations in the radial component of the field near the ∼11 hour planetary period associated with north-south motions of the current sheet are ubiquitous in these data. Here, we examine and model the phase of these oscillations throughout the interval, taking account of both local time and radial propagation effects, and show that the oscillations exhibit dual periodicities. Those observed at distances exceeding ∼3 RS north of the modeled average center of the current sheet are found to oscillate near the modulation period of the northern Saturn kilometric radiation (SKR) emissions, while those observed south of this location oscillate near the modulation period of the southern SKR emissions. The phasing in both cases is consistent with the sense of the associated rotating quasi-uniform perturbation fields within the quasi-dipolar "core" region. We determine the structure of the current sheet as a function of the modeled phases, the results implying that the form of the modulation varies significantly over the beat cycle of the two oscillations. When the two field oscillations are in phase, the current sheet oscillates north-south with a peak-to-peak amplitude of ∼3 RS. When they are in antiphase, however, the thickness of the current sheet is also strongly modulated during the oscillation by factors of ∼2.

2169-9380
Provan, G.
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Andrews, D.J.
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Arridge, C.S.
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Coates, A.J.
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Cowley, S.W.H.
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Cox, G.
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Dougherty, M.K.
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Jackman, C.M.
9bc3456c-b254-48f1-ade0-912c5b8b4529
Provan, G.
5de9f25e-ab6f-4c99-aeec-e45394a48a6b
Andrews, D.J.
bf6edd18-8012-41bf-bbb5-f2b09193b42e
Arridge, C.S.
2efb7acf-be5b-41b4-bade-8b4ff0d78236
Coates, A.J.
61022799-2e2b-46da-a964-23d9aaebe455
Cowley, S.W.H.
e8174910-ddcd-4a23-9d7c-0e1117def06c
Cox, G.
835fc80e-ed7b-4a74-9c0f-7a64c945c136
Dougherty, M.K.
aa297043-7e86-4501-952b-a6363edaaba8
Jackman, C.M.
9bc3456c-b254-48f1-ade0-912c5b8b4529

Provan, G., Andrews, D.J., Arridge, C.S., Coates, A.J., Cowley, S.W.H., Cox, G., Dougherty, M.K. and Jackman, C.M. (2012) Dual periodicities in planetary-period magnetic field oscillations in Saturn's tail. Journal of Geophysical Research: Space Physics, 117 (1), [A01209]. (doi:10.1029/2011JA017104).

Record type: Article

Abstract

We examine magnetic field data from 10 apoapsis passes of the Cassini spacecraft during 2006 when the spacecraft explored the midnight and dawn sectors of Saturn's magnetotail to down-tail distances of ∼65 RS (Saturn radius, RS, is 60,268 km). Oscillations in the radial component of the field near the ∼11 hour planetary period associated with north-south motions of the current sheet are ubiquitous in these data. Here, we examine and model the phase of these oscillations throughout the interval, taking account of both local time and radial propagation effects, and show that the oscillations exhibit dual periodicities. Those observed at distances exceeding ∼3 RS north of the modeled average center of the current sheet are found to oscillate near the modulation period of the northern Saturn kilometric radiation (SKR) emissions, while those observed south of this location oscillate near the modulation period of the southern SKR emissions. The phasing in both cases is consistent with the sense of the associated rotating quasi-uniform perturbation fields within the quasi-dipolar "core" region. We determine the structure of the current sheet as a function of the modeled phases, the results implying that the form of the modulation varies significantly over the beat cycle of the two oscillations. When the two field oscillations are in phase, the current sheet oscillates north-south with a peak-to-peak amplitude of ∼3 RS. When they are in antiphase, however, the thickness of the current sheet is also strongly modulated during the oscillation by factors of ∼2.

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Published date: 1 January 2012

Identifiers

Local EPrints ID: 437331
URI: http://eprints.soton.ac.uk/id/eprint/437331
ISSN: 2169-9380
PURE UUID: f71fd759-1b36-4335-aabd-e267e8ec084d
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: 10 Nov 2021 03:35

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Contributors

Author: G. Provan
Author: D.J. Andrews
Author: C.S. Arridge
Author: A.J. Coates
Author: S.W.H. Cowley
Author: G. Cox
Author: M.K. Dougherty
Author: C.M. Jackman ORCID iD

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