Related papers: From convective to stellar dynamos
Today, the generation of magnetic fields in solar-type stars and its relation to activity and rotation can coherently be explained, although it is certainly not understood in its entirety. Rotation facilitates the generation of magnetic…
Global and semi-global convective dynamo simulations of solar-like stars are known to show a transition from an anti-solar (fast poles, slow equator) to solar-like (fast equator, slow poles) differential rotation (DR) for increasing…
Mean-field dynamo theory has important applications in solar physics and galactic magnetism. We discuss some of the many turbulence effects relevant to the generation of large-scale magnetic fields in the solar convection zone. The…
Some common properties of helical magnetic fields in decaying and driven turbulence are discussed. These include mainly the inverse cascade that produces fields on progressively larger scales. Magnetic helicity also restricts the evolution…
Recent numerical simulations by Freytag et al. of the outer convection envelope of the cool super-giant Betelgeuse, have shown that the fluctuations in the star's apparent luminosity may be caused by giant cell convection. These simulations…
We explore effects of random non-axisymmetric perturbations of kinetic helicity (the $\alpha$ effect) and diffusive decay of bipolar magnetic regions on generation and evolution of large-scale non-axisymmetric magnetic fields on the Sun.…
Numerical simulations are an important tool in furthering our understanding of turbulent dynamo action, a process that occurs in a vast range of astrophysical bodies. It is important in all computational work that comparisons are made…
Context: Convectively-driven flows play a crucial role in the dynamo processes that are responsible for producing magnetic activity in stars and planets. It is still not fully understood why many astrophysical magnetic fields have a…
Several solar-like stars exhibit cyclic magnetic activity similar to the Sun as found in photospheric and chromospheric emission. We want to understand the physical mechanism involved in rotational dependence of these activity cycle…
Combined action of helical motions of plasma (the $\alpha$ effect) and non-uniform (differential) rotation is a key dynamo mechanism of solar and galactic large-scale magnetic fields. Dynamics of magnetic helicity of small-scale fields is a…
Stably stratified fluid layers are common in gaseous planets, stellar interiors, and planetary cores, and have long been considered incapable of sustaining dynamo action. Here, we show that semiconvection - driven by a destabilizing thermal…
Large-scale magnetic fields in galaxies are thought to be generated by a turbulent dynamo. However the same turbulence also leads to a small-scale dynamo which generates magnetic noise at a more rapid rate. The efficiency of the large-scale…
Mean-field dynamo theory suggests that turbulent convection in a rotating layer of electrically-conducting fluid produces a significant alpha-effect, which is one of the key ingredients in any mean-field dynamo model. Provided that this…
We demonstrate that a magneto-convection simulation incorporating essential physical processes governing solar surface convection exhibits turbulent small-scale dynamo action. By presenting a derivation of the energy balance equation and…
In this paper we first discuss observational evidence of longitudinal concentrations of magnetic activity in the Sun and rapidly rotating late-type stars with outer convective envelopes. Scenarios arising from the idea of rotationally…
Spectropolarimetric observations show that many low-mass stars possess large-scale poloidal magnetic fields with considerable dipole component, which in some cases exhibit temporal dynamics - cycles or reversals. Although it is widely…
Our theoretical and numerical analysis have suggested that for low-mass main sequences stars (of the spectral classes from M5 to G0) rotating much faster than the Sun, the generated large-scale magnetic field is caused by the mean-field…
The degree of intermittency of the magnetic field of a large-scale dynamo is considered. Based on simulations it is argued that there is a tendency for the field to become more diffuse and non-intermittent as the dynamo saturates. The…
Context: Large-scale magnetic fields resulting from hydromagnetic dynamo action may differ substantially in their time dependence. Cyclic field variations, characteristic for the solar magnetic field, are often explained by an important…
Using simulations of slowly rotating stratified turbulence, we show that the alpha effect responsible for the generation of astrophysical magnetic fields is proportional to the logarithmic gradient of kinetic energy density rather than that…