Dipolar versus multipolar dynamos: the influence of the background density stratification

  title={Dipolar versus multipolar dynamos: the influence of the background density stratification},
  author={Thomas Gastine and Luc{\'i}a Duarte and Johannes Wicht},
  journal={Astronomy and Astrophysics},
Context: dynamo action in giant planets and rapidly rotating stars leads to a broad variety of magnetic field geometries including small scale multipolar and large scale dipole-dominated topologies. Previous dynamo models suggest that solutions become multipolar once inertia becomes influential. Being tailored for terrestrial planets, most of these models neglected the background density stratification. Aims: we investigate the influence of the density stratification on convection-driven dynamo… 
Dipolar dynamos in stratified systems
Observations of low-mass stars reveal a variety of magnetic field topologies ranging from large-scale, axial dipoles to more complex magnetic fields. At the same time, three-dimensional spherical
Dipole collapse in rotating stratified dynamos
Numerical modelling of convection driven dynamos in the Boussinesq approximation revealed fundamental characteristics of the dynamo-generated magnetic fields, but the relevance of these results
What controls the magnetic geometry of M dwarfs
Context: observations of rapidly rotating M dwarfs show a broad variety of large-scale magnetic fields encompassing dipole-dominated and multipolar geometries. In dynamo models, the relative
A dynamo model of Jupiter’s magnetic field
We present results from simulations of rotating magnetized turbulent convection in spherical wedge geometry representing parts of the latitudinal and longitudinal extents of a star. Here we consider
Transition from axi- to nonaxisymmetric dynamo modes in spherical convection models of solar-like stars
Context. Both dynamo theory and observations of stellar large-scale magnetic fields suggest a change from nearly axisymmetric configurations at solar rotation rates to nonaxisymmetric configurations
Dynamo Action in the Steeply Decaying Conductivity Region of Jupiter‐Like Dynamo Models
The Juno mission is delivering spectacular data of Jupiter's magnetic field, while the gravity measurements finally allow constraining the depth of the winds observed at cloud level. However, to
Helicity inversion in spherical convection as a means for equatorward dynamo wave propagation
We discuss here a purely hydrodynamical mechanism to invert the sign of the kinetic helicity, which plays a key role in determining the direction of propagation of cyclical magnetism in most models


Dipole Collapse and Dynamo Waves in Global Direct Numerical Simulations
Magnetic fields of low-mass stars and planets are thought to originate from self-excited dynamo action in their convective interiors. Observations reveal a variety of field topologies ranging from
Scaling properties of convection-driven dynamos in rotating spherical shells and application to planetary magnetic fields
SUMMARY We study numerically an extensive set of dynamo models in rotating spherical shells, varying all relevant control parameters by at least two orders of magnitude. Convection is driven by a
Simulations of Core Convection in Rotating A-Type Stars: Magnetic Dynamo Action
Core convection and dynamo activity deep within rotating A-type stars of 2 M☉ are studied with three-dimensional nonlinear simulations. Our modeling considers the inner 30% by radius of such stars,
On the relationship between zonal jets and dynamo action in giant planets
Jupiter and Saturn exhibit similar large‐scale dynamical features. Each planet has a prograde equatorial jet and a deeply seated dipolar magnetic field. Compared to Jupiter, Saturn's jet is broader
Effects of compressibility on driving zonal flow in gas giants
Simulations of Dynamo Action in Fully Convective Stars
We present three-dimensional nonlinear magnetohydrodynamic simulations of the interiors of fully convective M dwarfs. Our models consider 0.3 solar-mass stars using the Anelastic Spherical Harmonic
Numerical modeling of the geodynamo: Mechanisms of field generation and equilibration
Numerical calculations of fluid dynamos powered by thermal convection in a rotating, electrically conducting spherical shell are analyzed. We find two regimes of nonreversing, strong field dynamos at