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Induced magnetic moments from a nearly spherical ocean
Marshall J Styczinski1,2, Erika M Harnett2,3
1Department of Physics, University of Washington, Box 351560, 3910 15th Ave NE, Seattle, WA 98195-1560, USA.
Icarus
|February 9, 2022
Summary
This study models induced magnetic fields in non-spherical, conductive bodies like moons. It reveals that magnetic moments from shape irregularities are independent, allowing for accurate analysis of planetary magnetic fields and satellite interactions.
Area of Science:
- Planetary Science
- Geophysics
- Electromagnetism
Background:
- Large planets possess strong magnetic fields interacting with conductive moons.
- Time-varying magnetic fields induce secondary fields in conductive bodies via eddy currents.
- Previous models assumed spherical symmetry for simplicity.
Purpose of the Study:
- To determine the induced magnetic field for near-spherical conductors with non-spherical boundaries.
- To develop a method for analyzing magnetic field interactions with non-spherical moons.
- To enable accurate interpretation of magnetic measurements from missions like Europa Clipper.
Main Methods:
- Expanded the conductor's outer boundary in spherical harmonics.
- Applied approximations for uniform excitation fields and large body dimensions.
- Derived magnetic solutions based on superposition of induced moments from each harmonic.
Main Results:
- Each spherical harmonic in the shape expansion induces independent magnetic moments.
- Simple superposition applies to magnetic moments induced by shape perturbations.
- Provided a table of induced magnetic moments and a general formula for arbitrary shapes.
Conclusions:
- The study enables magnetic field analysis for non-spherical oceans on moons for the first time.
- Accounting for non-spherical boundaries is crucial for interpreting magnetic data from moons like Europa.
- This work advances our understanding of electromagnetic interactions within planetary systems.
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