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Saturn's magnetospheric refresh rate

Saturn's magnetospheric refresh rate
Saturn's magnetospheric refresh rate

A 2-3 day periodicity observed in Jupiter's magnetosphere (superposed on the giant planet's 9.5 h rotation rate) has been associated with a characteristic mass-loading/unloading period at Jupiter. We follow a method derived by Kronberg et al. () and find, consistent with their results, that this period is most likely to fall between 1.5 and 3.9 days. Assuming the same process operates at Saturn, we argue, based on equivalent scales at the two planets, that its period should be 4 to 6 times faster at Saturn and therefore display a period of 8 to 18 h. Applying the method of Kronberg et al. for the mass-loading source rates estimated by Smith et al. () based on data from the third and fifth Cassini-Enceladus encounters, we estimate that the expected magnetospheric refresh rate varies from 8 to 31 h, a range that includes Saturn's rotation rate of ∼10.8 h. The magnetospheric period we describe is proportional to the total mass-loading rate in the system. The period is, therefore, faster (1) for increased outgassing from Enceladus, (2) near Saturn solstice (when the highest proportion of the rings is illuminated), and (3) near solar maximum when ionization by solar photons maximizes. We do not claim to explain the few percent jitter in period derived from Saturn Kilometric Radiation with this model, nor do we address the observed difference in period observed in the north and south hemispheres.

Jupiter, magnetosphere, period, plasma, Saturn, substorm
0094-8276
2479-2483
Rymer, A.M.
1edf75af-6992-4881-8604-4acb5c5362ca
Mitchell, D.G.
db8219f7-bb81-4018-b5e3-c478527aca4c
Hill, T.W.
8627ecb2-6e74-447e-99e7-ab68cd86ab9a
Kronberg, E.A.
1de51184-0fa8-4fb9-9c83-60fb9e21be2c
Krupp, N.
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Jackman, C.M.
9bc3456c-b254-48f1-ade0-912c5b8b4529
Rymer, A.M.
1edf75af-6992-4881-8604-4acb5c5362ca
Mitchell, D.G.
db8219f7-bb81-4018-b5e3-c478527aca4c
Hill, T.W.
8627ecb2-6e74-447e-99e7-ab68cd86ab9a
Kronberg, E.A.
1de51184-0fa8-4fb9-9c83-60fb9e21be2c
Krupp, N.
81e8ae1f-7fab-4ea8-b8d3-44c5a489c283
Jackman, C.M.
9bc3456c-b254-48f1-ade0-912c5b8b4529

Rymer, A.M., Mitchell, D.G., Hill, T.W., Kronberg, E.A., Krupp, N. and Jackman, C.M. (2013) Saturn's magnetospheric refresh rate. Geophysical Research Letters, 40 (11), 2479-2483. (doi:10.1002/grl.50530).

Record type: Article

Abstract

A 2-3 day periodicity observed in Jupiter's magnetosphere (superposed on the giant planet's 9.5 h rotation rate) has been associated with a characteristic mass-loading/unloading period at Jupiter. We follow a method derived by Kronberg et al. () and find, consistent with their results, that this period is most likely to fall between 1.5 and 3.9 days. Assuming the same process operates at Saturn, we argue, based on equivalent scales at the two planets, that its period should be 4 to 6 times faster at Saturn and therefore display a period of 8 to 18 h. Applying the method of Kronberg et al. for the mass-loading source rates estimated by Smith et al. () based on data from the third and fifth Cassini-Enceladus encounters, we estimate that the expected magnetospheric refresh rate varies from 8 to 31 h, a range that includes Saturn's rotation rate of ∼10.8 h. The magnetospheric period we describe is proportional to the total mass-loading rate in the system. The period is, therefore, faster (1) for increased outgassing from Enceladus, (2) near Saturn solstice (when the highest proportion of the rings is illuminated), and (3) near solar maximum when ionization by solar photons maximizes. We do not claim to explain the few percent jitter in period derived from Saturn Kilometric Radiation with this model, nor do we address the observed difference in period observed in the north and south hemispheres.

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More information

Published date: 16 June 2013
Keywords: Jupiter, magnetosphere, period, plasma, Saturn, substorm

Identifiers

Local EPrints ID: 437314
URI: http://eprints.soton.ac.uk/id/eprint/437314
ISSN: 0094-8276
PURE UUID: 196fb88f-d48e-4b83-9f93-7ac3d150dff3
ORCID for C.M. Jackman: ORCID iD orcid.org/0000-0003-0635-7361

Catalogue record

Date deposited: 24 Jan 2020 17:31
Last modified: 10 Nov 2021 03:35

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Contributors

Author: A.M. Rymer
Author: D.G. Mitchell
Author: T.W. Hill
Author: E.A. Kronberg
Author: N. Krupp
Author: C.M. Jackman ORCID iD

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