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Magnetic Induction in Convecting Galilean Oceans
  • +4
  • Steven Douglas Vance,
  • Bruce G Bills,
  • Corey J Cochrane,
  • Krista M. Soderlund,
  • N. Gómez-Pérez,
  • M. J Styczinski,
  • Carol S Paty
Steven Douglas Vance
Jet Propulsion Laboratory, California Institute of Technology, Jet Propulsion Laboratory, California Institute of Technology

Corresponding Author:svance@jpl.caltech.edu

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Bruce G Bills
Jet Propulsion Laboratory, California Institute of Technology, Jet Propulsion Laboratory, California Institute of Technology
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Corey J Cochrane
Jet Propulsion Laboratory, California Institute of Technology, Jet Propulsion Laboratory, California Institute of Technology
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Krista M. Soderlund
University of Texas at Austin, University of Texas at Austin
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N. Gómez-Pérez
British Geologic Survey, British Geologic Survey
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M. J Styczinski
University of Washington, University of Washington
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Carol S Paty
University of Oregon, University of Oregon
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Abstract

To date, analyses of magnetic induction in putative oceans in Jupiter’s large icy moons have assumed uniform conductivity in the modeled oceans. However, the phase and amplitude response of the induced fields will be influenced by the increasing electrical conductivity along oceans’ convective adiabatic temperature profiles. Here, we examine the amplitudes and phase lags for magnetic diffusion in modeled oceans of Europa, Ganymede, and Callisto. We restrict our analysis to spherically symmetric configurations, treating interior structures based on self-consistent thermodynamics, accounting for variations in electrical conductivity with depth in convective oceans \citep{Vance_2018}. The numerical approach considers tens of radial layers. The induction response of the adiabatic conductivity profile differs from that of an ocean with uniform conductivity set to that at the ice-ocean interface, or to the mean value of the adiabatic profile, by more than 10\% in many cases. We compare these modeled signals with magnetic fields induced by oceanic fluid motions that might be used to measure oceanic flows \citep[e.g.,][]{Chave83,Tyler11,Minami17}. For turbulent convection \citep{soderlund2014ocean}, we find that these signals can dominate induction signal at low latitudes, underscoring the need for spatial coverage in magnetic investigations. Based on end-member ocean compositions \citep{zolotov2008oceanic,zolotov2009chemical}, we quantify the residual magnetic induction signals that might be used to infer the oxidation state of Europa’s ocean and to investigate stable liquids under high-pressure ices in Ganymede and Callisto. Fully exploring this parameter space for the sake of planned missions requires electrical conductivity measurements in fluids at low temperature and to high salinity and pressure.
Feb 2021Published in Journal of Geophysical Research: Planets volume 126 issue 2. 10.1029/2020JE006418