Concentration of toroidal magnetic field in the solar tachocline by η-quenching

  title={Concentration of toroidal magnetic field in the solar tachocline by $\eta$-quenching},
  author={Peter A. Gilman and Matthias Rempel},
  journal={The Astrophysical Journal},
We show that if the turbulent magnetic diffusivity used in solar dynamos is assumed to be "quenched" by increasing toroidal fields, much larger amplitude and more concentrated toroidal fields can be induced by differential rotation from an assumed poloidal field than if there is no quenching. This amplification and concentration mechanism is weakened and bounded by j × B feedbacks on the differential rotation. Nevertheless, it is strong enough to contribute to the creation of ~100 kG toroidal… 

Figures from this paper

The possible magnetic torus in stellar interior
Various possibilities of the structure of the magnetic field, which is driven by turbulent dynamo mechanisms, in the stellar convection zone are analysed, putting an emphasis on the cross-helicity
The turbulent diffusion of toroidal magnetic flux as inferred from properties of the sunspot butterfly diagram
Context. In order to match observed properties of the solar cycle, flux-transport dynamo models require the toroidal magnetic flux to be stored in a region of low magnetic diffusivity, typically
Non-kinematic Flux-transport Dynamos Including the Effects of Diffusivity Quenching
Turbulent magnetic diffusivity is quenched when strong magnetic fields suppress turbulent motion in a phenomenon known as diffusivity quenching. Diffusivity quenching can provide a mechanism for
Constraints on the Magnetic Buoyancy Instabilities of a Shear-Generated Magnetic Layer
In a recent paper addressing the solar Ω-effect, we found that the action of forced vertical (radial) shear on the vertical component of poloidal magnetic field could induce magnetic buoyancy that
The role of diffusivity quenching in flux-transport dynamo models
In the nonlinear phase of a dynamo process, the back-reaction of the magnetic field upon the turbulent motion results in a decrease of the turbulence level and therefore in a suppression of both the
Global MHD Instabilities in a Three-dimensional Thin-Shell Model of Solar Tachocline
We generalize the linear analysis of the global instability of coexisting differential rotation and toroidal magnetic fields in the solar tachocline to include continuous radial stratification,
Magnetic field amplification in proto-neutron stars. The role of the neutron-finger instability for
Aims. During the first 40 s after their birth, proto-neutron stars are expected to be subject to at least two types of instability. The first one, the convective instability, is excited in the inner
A Shallow-Water Theory for the Sun’s Active Longitudes
We show that the global MHD shallow-water instability of differential rotation and toroidal field bands in the solar tachocline provides a possible mechanism for the formation and evolution of active
Flux-Transport Dynamos with Lorentz Force Feedback on Differential Rotation and Meridional Flow: Saturation Mechanism and Torsional Oscillations
In this paper we discuss a dynamic flux-transport dynamo model that includes the feedback of the induced magnetic field on differential rotation and meridional flow. We consider two different
Towards better constrained models of the solar magnetic cycle
The best tools we have for understanding the origin of solar magnetic variability are kinematic dynamo models. During the last decade, this type of models has seen a continuous evolution and has


Intensification of Magnetic Fields by Conversion of Potential Energy
A strong superequipartition magnetic field strength on the order of 10 T (105 G) has been inferred at the bottom of the solar convection zone. We show that the explosion of weak magnetic flux tubes,
Nonlinear Restrictions on Dynamo Action
Astrophysical dynamos operate in the limit of small magnetic diffusivity. In order for magnetic reconnection to occur, very small magnetic structures must form so that diffusion becomes effective.
The influence of the Coriolis force on flux tubes rising through the solar convection zone
In order to study the effect of the Coriolis force due to solar rotation on rising magnetic flux, the authors consider a flux ring, azimuthally symmetric around the rotation axis, starting from rest
Dynamics of emerging active region flux loops
The buoyant rise of a magnetic flux loop arising from a single perturbed segment of a toroidal flux ring lying slightly beneath the base of the convection zone is studied by way of numerical
Dynamo Models with Magnetic Diffusivity-Quenching.
Abstract The magnetic influence on a turbulent plasma also produces a complicated structure of the eddy diffusivity tensor rather than a simple and traditional quenching of the eddy diffusivity.
Emerging Flux Tubes in the Solar Convection Zone. II. The Influence of Initial Conditions
Numerical simulations of rising magnetic flux tubes in the solar convection zone have contributed significantly to our understanding of the basic properties of sunspot groups. They have provided an
Solar differential rotation and meridional flow: The role of a subadiabatic tachocline for the taylor-proudman balance
We present a simple model for the solar differential rotation and meridional circulation based on a mean field parameterization of the Reynolds stresses that drive the differential rotation. We
Turbulent Convection under the Influence of Rotation: Sustaining a Strong Differential Rotation
The intense turbulence present in the solar convection zone is a major challenge to both theory and simulation as one tries to understand the origins of the striking differential rotation profile
A Babcock-Leighton Flux Transport Dynamo with Solar-like Differential Rotation
We investigate the properties of a kinematic —ux transport solar dynamo model. The model is charac- terized by a solar-like internal diUerential rotation pro—le, a single-cell meridional —ow in the
Three-dimensional Spherical Simulations of Solar Convection. I. Differential Rotation and Pattern Evolution Achieved with Laminar and Turbulent States
Rotationally constrained convection possesses velocity correlations that transport momentum and drive mean —ows such as diUerential rotation. The nature of this transport can be very complex in