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  Anelastic spherical dynamos with radially variable electrical conductivity

Dietrich, W., & Jones, C. A. (2018). Anelastic spherical dynamos with radially variable electrical conductivity. Icarus, 305, 15-32. doi:10.1016/j.icarus.2018.01.003.

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 Creators:
Dietrich, Wieland1, Author              
Jones, C. A. , Author
Affiliations:
1Department Planets and Comets, Max Planck Institute for Solar System Research, Max Planck Society, ou_1832288              

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 MPIS_PROJECTS: Planetary Dynamics
 MPIS_GROUPS: Planets and Comets
 Abstract: A series of numerical simulations of the dynamo process operating inside gas giant planets has been performed. We use an anelastic, fully nonlinear, three-dimensional, benchmarked MHD code to evolve the flow, entropy and magnetic field. Our models take into account the varying electrical conductivity, high in the ionised metallic hydrogen region, low in the molecular outer region. Our suite of electrical conductivity profiles ranges from Jupiter-like, where the outer hydrodynamic region is quite thin, to Saturn-like, where there is a thick non-conducting shell. The rapid rotation leads to the formation of two distinct dynamical regimes which are separated by a magnetic tangent cylinder - mTC. Outside the mTC there are strong zonal flows, where Reynolds stress balances turbulent viscosity, but inside the mTC Lorentz force reduces the zonal flow. The dynamic interaction between both regions induces meridional circulation. We find a rich diversity of magnetic field morphologies. There are Jupiter-like steady dipolar fields, and a belt of quadrupolar dominated dynamos spanning the range of models between Jupiter-like and Saturn-like conductivity profiles. This diversity may be linked to the appearance of reversed sign helicity in the metallic regions of our dynamos. With Saturn-like conductivity profiles we find models with dipolar magnetic fields, whose axisymmetric components resemble those of Saturn, and which oscillate on a very long time-scale. However, the non-axisymmetric field components of our models are at least ten times larger than those of Saturn, possibly due to the absence of any stably stratified layer.

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Language(s): eng - English
 Dates: 2018-01-102018
 Publication Status: Published in print
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1016/j.icarus.2018.01.003
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Title: Icarus
Source Genre: Journal
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Publ. Info: Amsterdam : Academic Press
Pages: - Volume / Issue: 305 Sequence Number: - Start / End Page: 15 - 32 Identifier: ISSN: 0019-1035
CoNE: https://pure.mpg.de/cone/journals/resource/954922645023