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Magnetic Induction Responses of Jupiter's Ocean Moons Including Effects from Adiabatic Convection
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  • 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

Prior analyses of oceanic magnetic induction within Jupiter’s large icy moons have assumed uniform electrical conductivity. However, the phase and amplitude responses of the induced fields will be influenced by the natural depth-dependence of the electrical conductivity. Here, we examine the amplitudes and phase delays for magnetic diffusion in modeled oceans of Europa, Ganymede, and Callisto. For spherically symmetric configurations, we consider thermodynamically consistent interior structures that include realistic electrical conductivity along the oceans’ adiabatic temperature profiles. Conductances depend strongly on salinity, especially in the large moons. The induction responses of the adiabatic profiles differ from those of oceans with uniform conductivity set to values at the ice–ocean interface, or to the mean values of the adiabatic profile, by more than 10\% for some signals. We also consider motionally induced magnetic fields generated by convective fluid motions within the oceans, which might optimistically be used to infer ocean flows or, pessimistically, act to bias the ocean conductivity inversions. Our upper-bound scaling estimates suggest this effect may be important at Europa and Ganymede, with a negligible contribution at Callisto. Based on end-member ocean compositions, we quantify the 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 thermodynamic and electrical conductivity measurements in fluids at low temperature and to high salinity and pressure as well as modeling of motional induction responses.
Feb 2021Published in Journal of Geophysical Research: Planets volume 126 issue 2. 10.1029/2020JE006418