Related papers: Dynamos in accretion discs
Cold optically thick accretion disks with hot coronae and radial advection have been investigated. Within the framework of $\alpha$-viscosity models, we assume that all the mass accretion and angular momentum transport take place in the…
Young stellar objects (YSOs) may not accumulate their mass steadily, as was previously thought, but in a series of violent events manifesting themselves as sharp stellar brightening. These events can be caused by fragmentation due to…
Star-forming galaxies like the Milky Way are surrounded by a hot gaseous halo at the virial temperature - the so-called galactic corona - that plays a fundamental role in their evolution. The interaction between the disc and the corona has…
It has long been accepted that a possible mechanism for explaining the existence of magnetic white dwarfs is the merger of a binary white dwarf system, as there are viable mechanisms for producing sustainable magnetic fields within the…
Magnetically active stars are the sites of efficient particle acceleration and plasma heating, processes that have been studied in detail in the solar corona. Investigation of such processes in young stellar objects is much more challenging…
We present an instability occurring in the inner part of disks threaded by a moderately strong vertical (poloidal) magnetic field. Its mechanism is such that a spiral density wave in the disk, driven by magnetic stresses (rather than…
A large body of theoretical and computational work shows that jets - modelled as magnetized disk winds - exert an external torque on their underlying disks that can efficiently remove angular momentum and act as major drivers of disk…
The inner region of the accretion disk onto a rotating magnetized central star (neutron star, white dwarf or T Tauri star) is subjected to magnetic torques which induce warping and precession of the disk. The origin of these torques lies in…
According to the magnetospheric accretion scenario, young low-mass stars are surrounded by circumstellar disks which they interact with through accretion of mass. The accretion builds up the star to its final mass and is also believed to…
We argue that resonant friction has a dramatic effect on a disc whose rotation direction is misaligned with that of its host nuclear star cluster. The disc's gravity causes gravitational perturbation of the cluster that in turn exerts a…
Current theoretical models for the outflows/jets from AGN, X-ray binaries and young stellar objects involve large-scale magnetic fields threading an underlying accretion disk. We suggest that such a disk is subjected to warping instability…
Rotation period measurements of low-mass stars show that the spin distributions in young clusters do not exhibit the spin-up expected due to contraction, during the phase when a large fraction of stars are still surrounded by accretion…
There is increasing evidence that low mass stars with circumstellar disks can be born close to massive stars, in some cases within tenths of a pc. If the disks have lifetimes greater than those of the more massive stars, they are exposed to…
Classical T Tauri stars are low mass young forming stars that are surrounded by a circumstellar accretion disc from which they gain mass. Despite this accretion and their own contraction that should both lead to their spin up, these stars…
Accreting pulsars power relativistic jets, and display a complex spin phenomenology. These behaviours may be closely related to the large-scale configuration of the star's magnetic field, shaped by its interaction with the surrounding…
A long-standing question in active galactic nucleus (AGN) research is how the corona is heated up to produce X-ray radiation much stronger than that arising from the viscous heating within the corona. In this paper, we carry out detailed…
I review, from an observational perspective, the interactions of accretion discs with magnetic fields in cataclysmic variable stars. I start with systems where the accretion flows via a stream, and discuss the circumstances in which the…
Millisecond x-ray pulsars have weak magnetic dipole moments of $\sim 10^{16}$\,T\,m$^3$ compared to ordinary X-ray pulsars with dipole moments of $10^{20}$\,T\,m$^3$. For this reason a surrounding accretion disc can extend closer to the…
Aspects of turbulence in protostellar accretion discs are being reviewed. The emergence of dead zones due to poor ionization and alternatives to the magneto-rotational instability are discussed. The coupling between dust and gas in…
The known exoplanet population displays a great diversity of orbital architectures, and explaining the origin of this is a major challenge for planet formation theories. The gravitational interaction between young planets and their…