Recipe for a Saturn‐Like Dynamo. Issue 2 (5th May 2021)

• Record Type: Journal Article
• Authors: Yan, C.; Stanley, S.
• Is Part Of: AGU advances. Volume 2:Issue 2(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-05-05
• Subjects: dynamos -- helium immiscibility layer -- numerical simulations -- planetary magnetic field -- Saturn's interior; Earth sciences -- Periodicals; Space sciences -- Periodicals; 550
• DOI: 10.1029/2020AV000318
• Languages: English
• ISSNs: 2576-604X

Abstract

Abstract: The Cassini Grand Finale orbits provided detailed observations of Saturn's internal magnetic field. Unique characteristics of the observed field, such as its axisymmetry and power spectrum, provide constraints on dynamo processes deep in Saturn's interior. Here, we use numerical dynamo simulations to explore what ingredients are necessary in a dynamo in order to produce the unique "Saturn‐like" surface magnetic field. We find that characteristics of Saturn's magnetic field can be sensitive to properties of a stably stratified helium rain‐out layer and thermal perturbations at the top of the layer. Our best models suggest that a relatively thick stably stratified helium rain‐out layer may extend out to 70% of Saturn's radius, likely imprinted with weak heat flux out of the equatorial region and strong heat flux out of high latitudes. These results may provide new constraints on stable stratification inside Saturn and its thermal evolution. Plain Language Summary: Detailed measurements from the Grand Finale orbits of the Cassini mission show distinctive features of Saturn's magnetic field. These features provide critical constraints on Saturn's deep interior where its magnetic field is generated. Here, we use dynamo simulations to explore whether the implementation of a helium rain layer at the top of the dynamo region that is stable to convection, as well as different thermal perturbation patterns at the top of the layer, could help reproduce a magnetic field resembling Saturn's surface magnetic field features. We find that a relatively thick stable layer extending out to 70% of Saturn's radius is favorable in reproducing features of Saturn's surface magnetic field, with weak heat flux out of the equatorial region and strong heat flux out of high latitudes at the top of the stable layer. Key Points: We carry out numerical dynamo simulations to explain unique features of Saturn's magnetic field, such as its axisymmetry and power spectrum We investigate the spatial and temporal effects of a helium immiscibility layer on the resulting magnetic field We find a relatively thick stable layer and specific thermal perturbations are needed to match observations from Cassini Grand Finale