相关论文: A global galactic dynamo with a corona constrained…
The Sun is a magnetic star, and the only spatio-temporally resolved astrophysical system displaying turbulent MHD thermal convection. This makes it a privileged object of study to understand fluid turbulence in extreme regimes and its…
Magnetic fields generated in the Sun's interior by the solar dynamo mechanism drive solar activity over a range of time-scales. While space-based observations of the Sun's corona exist only for few decades, direct sunspot observations exist…
Local magnetic reversals are an inseparable part of magnetohydrodynamic (MHD) turbulence whose collective outcome on an arbitrary scale in the inertial range may lead to a global stochastic reconnection event with a rate independent of…
The evolution of magnetic fields is studied using simulations of forced helical turbulence with strong imposed shear. After some initial exponential growth, the magnetic field develops a large scale travelling wave pattern. The resulting…
Stellar winds are an integral part of the underlying dynamo, the motor of stellar activity. The wind controls the star's angular momentum loss, which depends on the magnetic field geometry which varies significantly in time and latitude.…
Helioseismology provides important constraints for the solar dynamo problem. However, the basic properties and even the depth of the dynamo process, which operates also in other stars, are unknown. Most of the dynamo models suggest that the…
Irregular galaxies are usually smaller and less massive than their spiral, S0, and elliptical counterparts. Radio observations indicate that a magnetic field is present in irregular galaxies whose value is similar to that in spiral…
Solar atmosphere is a single system unified by the presence of large-scale magnetic fields. Topological changes in magnetic fields that occur in one place may have consequences for coronal heating and eruptions for other, even remote…
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…
A new mechanism to form a magnetic pressure supported, high temperature corona above the photosphere of an accretion disk is explored using three dimensional radiation magneto-hydrodynamic (MHD) simulations. The thermal properties of the…
Much work on turbulent three-dimensional dynamos has been done using triply periodic domains, in which there are no magnetic helicity fluxes. Here we present simulations where the turbulent intensity is still nearly homogeneous, but now…
For over 30 years, the Magneto-Rotational Instability has been accepted as the mechanism driving accretion disk turbulence. Its physical basis is well understood, where an interplay between centrifugal forces and magnetic tension transfers…
Context. Photospheric motions shuffle the footpoints of the strong axial magnetic field that threads coronal loops giving rise to turbulent nonlinear dynamics characterized by the continuous formation and dissipation of field-aligned…
We give a short introduction to the subject and review advances in understanding the basic ingredients of the mean-field dynamo theory. The discussion includes the recent analytic and numerical work in developments for the mean…
The theory of large scale dynamos is reviewed with particular emphasis on the magnetic helicity constraint in the presence of closed and open boundaries. In the presence of closed or periodic boundaries, helical dynamos respond to the…
Solar magnetic activity shows both smooth secular changes, such as the Grand Modern Maximum, and quite abrupt drops that are denoted as Grand Minima. Direct numerical simulations (DNS) of convection driven dynamos offer one way of examining…
Many astrophysical bodies harbor magnetic fields that are thought to be sustained by a dynamo process. However, it has been argued that the production of large-scale magnetic fields by mean-field dynamo action is strongly suppressed at…
This paper is devoted to self-consistent modeling of the magnetically supported accretion disk with optically thick warm corona based on first principles. In our model, we consider the gas heating by magneto-rotational instability (MRI)…
We use three-dimensional direct numerical simulations of the helically forced magnetohydrodynamic equations in spherical shell segments in order to study the effects of changes in the geometrical shape and size of the domain on the growth…
We use idealized three-dimensional hydrodynamic simulations of global galactic discs to study the launching of galactic winds by supernovae (SNe). The simulations resolve the cooling radii of the majority of supernova remnants (SNRs) and…