Two models of the surface magnetic field of Saturn
Top: the surface magnetic field for the preferred model with a stably stratified layer and enhanced polar cooling. The field is very symmetrical, as is observed for Saturn. Bottom: the result with no stable layer and uniform cooling, illustrating a more non-symmetric field than is observed. Credit: Yan and Stanley [2021], Figure 5a and 5c
Source: AGU Advances

The final stages of the Cassini spacecraft mission allowed the magnetic field of Saturn to be carefully mapped. The field is amazingly symmetrical, much more so than any other planetary body. Although the reasons for this symmetry are unknown, it must be a result of Saturn’s internal structure.

Yan and Stanley [2021] suggest that the field’s characteristics are a consequence of two factors. The first is the presence of a thick, stably stratified layer above the convecting dynamo region; this damps out the short-wavelength field characteristics. The second is stronger cooling of the stable layer at the poles, inducing thermal winds and producing a better match to the magnetic power spectrum.

A stably stratified layer was expected based on theoretical arguments about helium rain-out, so this paper strengthens those arguments. A remaining puzzle is what mechanism could be causing the thermal winds posited in this model.

Citation: Yan, C. & Stanley, S. [2021]. Recipe for a Saturn-like dynamo. AGU Advances, 2, e2020AV000318.

—Francis Nimmo, Editor, AGU Advances

Text © 2021. The authors. CC BY-NC-ND 3.0
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