A magnetically driven equatorial jet in Europa’s ocean

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Abstract

During recent decades, data from space missions have provided strong evidence of deep liquid oceans underneath a thin outer icy crust on several moons of Jupiter1,2, particularly Europa3,4. But these observations have also raised many unanswered questions regarding the oceanic motions generated under the ice, or the mechanisms leading to the geological features observed on Europa5,6. By means of direct numerical simulations of Europa’s interior, we show here that Jupiter’s magnetic field generates a retrograde oceanic jet at the equator, which may influence the global dynamics of Europa’s ocean and contribute to the formation of some of its surface features by applying a unidirectional torque on Europa’s ice shell.

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Fig. 1: Velocity field and ohmic currents.
Fig. 2: Galileo magnetometer data in the EPhiO coordinates (Europa-centred with x along the direction of corotation, y radially inward towards Jupiter, and z parallel to Jupiter’s rotation axis), compared with results from DNS using h = 147 km.
Fig. 3: Magnitude of the oceanic jet.
Fig. 4: Snapshot of the instantaneous azimuthal velocity field at r = Ri + h/2 from the seafloor, for Ek = 10−5, Pr = 12, Pm = 10−3, Λ = 10−3 and Ra = 109.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.

Change history

  • 24 April 2019

    In the version of this Letter originally published, the following ‘Journal peer review information’ was missing: “Nature Astronomy thanks Jason Goodman and the other anonymous reviewer(s) for their contribution to the peer review of this work.” This statement has now been added.

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Acknowledgements

The GO-J-MAG-3-RDR-HIGHRES-V1.02 dataset was obtained from the Planetary Data System. This work was granted access to the HPC resources of MesoPSL financed by the Region Ile de France and the project Equip@Meso (reference ANR-10-EQPX-29-01) of the programme Investissements d’Avenir supervised by the Agence Nationale pour la Recherche.

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C.G. conceived the presented idea and developed the theory. L.P. performed the numerical simulations. C.G. and L.P. performed the analysis of the results and contributed to the final manuscript.

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Correspondence to Christophe Gissinger.

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The authors declare no competing interests.

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Journal peer review information: Nature Astronomy thanks Jason Goodman and the other anonymous reviewer(s) for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

Supplementary Table 1, Supplementary Figures 1–3.

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Gissinger, C., Petitdemange, L. A magnetically driven equatorial jet in Europa’s ocean. Nat Astron 3, 401–407 (2019). https://doi.org/10.1038/s41550-019-0713-3

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