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No Evidence for Time Variation in Saturn’s Internal Magnetic Field

Moore, Kimberly M. and Bolton, Bryce and Cao, Hao and Dougherty, Michele K. and Bloxham, Jeremy (2021) No Evidence for Time Variation in Saturn’s Internal Magnetic Field. Planetary Science Journal, 2 (5). Art. No. 181. ISSN 2632-3338. doi:10.3847/psj/ac173c.

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The time variation of a planetary magnetic field can reveal important aspects of a planet's interior structure. Searching for time variation in planetary magnetic fields other than Earth has proved challenging owing to the small number of spacecraft missions flown to date, but such a detection may be possible given a sufficiently long baseline for comparison. Here we leverage 38 years of spacecraft magnetometer measurements to search for time variation in Saturn's internal magnetic field. To isolate the possible signal of time variation, we remove a contemporary high-resolution internal field model, derived from Cassini data, as well as a best-fitting external magnetodisk field model from each of four past mission data sets: Pioneer 11 (1979), Voyager 1 (1980), Voyager 2 (1981), and Cassini Saturn Orbit Insertion (2004). We then attempt to fit the resulting signal with an axisymmetric internal field model. Overall, we find no evidence of time variation on a multidecadal timescale. Our results lend support to the existence of a stably stratified layer in Saturn and have comparative planetology implications for Jupiter's interior structure and dynamics.

Item Type:Article
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URLURL TypeDescription ItemMagnetometer and coordinate system data ItemNASA Planetary Data System
Moore, Kimberly M.0000-0003-3162-437X
Bolton, Bryce0000-0002-9936-5071
Cao, Hao0000-0002-6917-8363
Dougherty, Michele K.0000-0002-9658-8085
Bloxham, Jeremy0000-0001-8556-2675
Additional Information:© 2021. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2020 December 10; revised 2021 June 7; accepted 2021 July 21; published 2021 September 7. Magnetometer and coordinate system data used throughout this work can be found on the Imperial College London MAGDA server ( and the NASA Planetary Data System at the Jet Propulsion Laboratory ( We are grateful to Professor Stan Cowley and Dr. Gabrielle Provan at the University of Leicester and Dr. John E. P. Connerney at the NASA Goddard Spaceflight Center for providing independent use of Pioneer 11 magnetometer data. This research was supported by the Heising-Simons Foundation 51 Pegasi b Fellowship; the Royal Society Research Professorship; and the Royal Society UK grant RP 180014.
Funding AgencyGrant Number
Heising-Simons Foundation51 Pegasi b Fellowship
Royal SocietyRP 180014
Subject Keywords:Saturn; Jupiter; Planetary interior; Planetary magnetosphere; Planetary science; Magnetic fields; Geomagnetic fields; Magnetic anomalies
Issue or Number:5
Classification Code:Unified Astronomy Thesaurus concepts: Saturn (1426); Jupiter (873); Planetary interior (1248); Planetary magnetosphere (997); Planetary science (1255); Magnetic fields (994); Geomagnetic fields (646); Magnetic anomalies (993)
Record Number:CaltechAUTHORS:20210914-225406723
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Official Citation:Kimberly M. Moore et al 2021 Planet. Sci. J. 2 181
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:110899
Deposited By: George Porter
Deposited On:16 Sep 2021 22:01
Last Modified:16 Sep 2021 22:01

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