Related papers: Stellar dynamo models with prominent surface toroi…
The large-scale magnetic field observed at the solar surface is produced by the interior dynamo process. Whether this surface field also provides the dominant seed for the subsequent dynamo cycle, however, remains controversial, with…
Magnetic fields in the solar corona are responsible for a wide range of phenomena. However, any direct measurements of the coronal magnetic fields are very difficult due to lack of suitable spectral lines, weak magnetic fields, and high…
We review recent advances in modeling global-scale convection and dynamo processes with the Anelastic Spherical Harmonic (ASH) code. In particular, we have recently achieved the first global-scale solar convection simulations that exhibit…
Star-disc coupling is considered in numerical models where the stellar field is not an imposed perfect dipole, but instead a more irregular self-adjusting dynamo-generated field. Using axisymmetric simulations of the hydromagnetic…
The solar magnetic field is the primary agent that drives solar activity and couples the Sun to the Heliosphere. Although the details of this coupling depend on the quantitative properties of the field, many important aspects of the corona…
Stellar radiative zones are typically assumed to be motionless in standard models of stellar structure but there is sound theoretical and observational evidence that this cannot be the case. We investigate by direct numerical simulations a…
Most of the planetary nebulae (PN) have bipolar or other non-spherically symmetric shapes. The presence of a magnetic field in the central star may be the reason for this lack of symmetry, but observational works published in the literature…
Magnetic fields are present in a wide variety of stars throughout the HR diagram and play a role at basically all evolutionary stages, from very-low-mass dwarfs to very massive stars, and from young star-forming molecular clouds and…
The surface magnetic fields of pre-main-sequence stars and zero-age main-sequence stars are notably strong, resulting in the generation of numerous spots and the emission of bright chromospheric lines. Rotational variations in magnetic…
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…
The presence of magnetic fields at the surfaces of many massive stars has been suspected for decades, to explain the observed properties and activity of OB stars. However, very few genuine high-mass stars had been identified as magnetic…
We explore the possibility that a magnetar may owe its strong magnetic field to a magnetized core which, as indicated by certain equations of state, may form due to phase transitions at high density mediated by strong interaction within a…
Context. The solar dynamo consists of a process that converts poloidal field to toroidal field followed by a process which creates new poloidal field from the toroidal field. Aims. Our aim is to observe the poloidal and toroidal fields…
OB stars exhibit various types of spectral variability associated with wind structures, including the apparently ubiquitous discrete absorption components (DACs). These are proposed to be caused by either magnetic fields or non-radial…
Virial theorem is important for understanding stellar structures. It produces an interesting connection between the magnetic energy and the gravitational one. Using the general form of the virial theorem including the magnetic field…
The propeller regime of disk accretion to a rapidly rotating magnetized star is investigated here for the first time by axisymmetric 2.5D magnetohydrodynamic simulations. An expanded, closed magnetosphere forms in which the magnetic field…
Twisted magnetic fields are frequently seen to emerge above the visible surface of the Sun. This emergence is usually associated with the rise of buoyant magnetic flux structures. Here we ask how magnetic fields from a turbulent large-scale…
Our understanding of large-scale magnetic fields in stellar radiative zones remains fragmented and incomplete. Such magnetic fields, which must be produced by some form of dynamo mechanism, are thought to dominate angular-momentum…
Observations of the Sun and solar-type stars continue to reveal phenomena whose understanding is very likely to require a nonlinear framework. Here we shall concentrate on two such phenomena, namely the grand minima type behaviour observed…
All cool main sequence stars including our Sun are thought to have magnetic fields. Observations of the Sun revealed that even in quiet regions small-scale turbulent magnetic fields are present. Simulations further showed that such magnetic…