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Large-scale dynamics of Saturn’s magnetopause: observations by Cassini

Large-scale dynamics of Saturn’s magnetopause: observations by Cassini
Large-scale dynamics of Saturn’s magnetopause: observations by Cassini
The long-term statistical behavior of the large-scale structure of Saturn's magnetosphere has been investigated. Established statistical techniques for Jupiter have been applied to the kronian system, employing Cassini magnetometer data and a new empirical shape model of the magnetopause based on these data. The resulting distribution of standoff distance RMP for Saturn, covering a time interval of ?400 days, is well-described by a “dual” or “bimodal” model—the sum of two normal distributions with different means at ?22 and ?27 planetary radii. We have made a comparison between the dual model's prediction for the probability distribution of solar wind dynamic pressure at Saturn with a sequence of observations from the Cassini Plasma Spectrometer (CAPS) instrument. Although the solar wind dynamic pressure observations are limited to a smaller time interval than the magnetometer data, we find that their overall range is in broad agreement with the that of the modeled pressures. However, the bimodal structure exhibited by the model is not apparent in the solar wind data for the corresponding range of dynamic pressures (?0.008 – 0.06 nPa), which suggests that other mechanisms at Saturn also influence the size distribution of the magnetopause. Considering internal processes at Saturn and their influence on magnetopause size, we conclude that the effect of internal mass loading and loss from the magnetospheric disk is plausibly able to explain the observed bimodal distribution in magnetopause standoff distance.
magnetosphere, saturn, magnetopause
2169-9380
A11209
Achilleos, N.
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Arridge, C.S.
cddea13c-2c2a-44c8-9607-309820a0fb0f
Bertucci, C.
61559df2-98e4-48a4-925e-38d33ab6891a
Jackman, C.M.
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Dougherty, M.K.
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Khurana, K.K.
13e3a0d9-2a06-4bff-8a6a-7de9a4e304e2
Russell, C.T.
0beb88bf-9d0e-4b75-80ae-61ba3776ce59
Achilleos, N.
2d7c619e-cbb3-4956-9769-cc99d2021296
Arridge, C.S.
cddea13c-2c2a-44c8-9607-309820a0fb0f
Bertucci, C.
61559df2-98e4-48a4-925e-38d33ab6891a
Jackman, C.M.
9bc3456c-b254-48f1-ade0-912c5b8b4529
Dougherty, M.K.
dfb81a1a-1b8d-4326-8416-5f66eb79e00a
Khurana, K.K.
13e3a0d9-2a06-4bff-8a6a-7de9a4e304e2
Russell, C.T.
0beb88bf-9d0e-4b75-80ae-61ba3776ce59

Achilleos, N., Arridge, C.S., Bertucci, C., Jackman, C.M., Dougherty, M.K., Khurana, K.K. and Russell, C.T. (2008) Large-scale dynamics of Saturn’s magnetopause: observations by Cassini. Journal of Geophysical Research: Space Physics, 113, A11209. (doi:10.1029/2008JA013265).

Record type: Article

Abstract

The long-term statistical behavior of the large-scale structure of Saturn's magnetosphere has been investigated. Established statistical techniques for Jupiter have been applied to the kronian system, employing Cassini magnetometer data and a new empirical shape model of the magnetopause based on these data. The resulting distribution of standoff distance RMP for Saturn, covering a time interval of ?400 days, is well-described by a “dual” or “bimodal” model—the sum of two normal distributions with different means at ?22 and ?27 planetary radii. We have made a comparison between the dual model's prediction for the probability distribution of solar wind dynamic pressure at Saturn with a sequence of observations from the Cassini Plasma Spectrometer (CAPS) instrument. Although the solar wind dynamic pressure observations are limited to a smaller time interval than the magnetometer data, we find that their overall range is in broad agreement with the that of the modeled pressures. However, the bimodal structure exhibited by the model is not apparent in the solar wind data for the corresponding range of dynamic pressures (?0.008 – 0.06 nPa), which suggests that other mechanisms at Saturn also influence the size distribution of the magnetopause. Considering internal processes at Saturn and their influence on magnetopause size, we conclude that the effect of internal mass loading and loss from the magnetospheric disk is plausibly able to explain the observed bimodal distribution in magnetopause standoff distance.

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e-pub ahead of print date: 13 November 2008
Published date: November 2008
Keywords: magnetosphere, saturn, magnetopause
Organisations: Astronomy Group

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Local EPrints ID: 358288
URI: https://eprints.soton.ac.uk/id/eprint/358288
ISSN: 2169-9380
PURE UUID: f79cebf3-1159-4f66-8a2d-6eabff7322a0

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Date deposited: 09 Oct 2013 13:27
Last modified: 28 Oct 2019 21:03

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