Related papers: Gravito-turbulence and dynamo in poorly ionised pr…
The origin of large-scale and coherent magnetic fields in astrophysical discs is an important and long standing problem. Researchers commonly appeal to a turbulent dynamo, sustained by the magneto-rotational instability (MRI), to supply the…
Gravitational instability (GI) features in several aspects of protostellar disk evolution, most notably in angular momentum transport, fragmentation, and the outbursts exemplified by FU Ori and EX Lupi systems. The outer regions of…
In the early stages of a protoplanetary disk, when its mass is a significant fraction of its star's, turbulence generated by gravitational instability (GI) should feature significantly in the disk's evolution. At the same time, the disk may…
The turbulence driven by gravitational instabilities (GIs) can amplify magnetic fields in massive gaseous disks. This GI dynamo may appear in young circumstellar disks, whose weak ionization challenges other amplification routes, as well as…
Gravitational instabilities (GIs) are most likely a fundamental process during the early stages of protoplanetary disc formation. Recently, there have been detections of spiral features in young, embedded objects that appear consistent with…
During early phases of a protoplanetary disks's life, gravitational instabilities can produce significant mass transport, can dramatically alter disk structure, can mix and shock-process gas and solids, and may be instrumental in planet…
The dynamics of solid bodies in protoplanetary disks are subject to the properties of any underlying gas turbulence. Turbulence driven by disk self-gravity shows features distinct from those driven by the magnetorotational instability…
Gravitational instability (GI) controls the dynamics of young massive protoplanetary discs. Apart from facilitating gas accretion on to the central protostar, it must also impact on the process of planet formation: directly through…
Protoplanetary gas disks are likely to experience gravitational instabilites (GI's) during some phase of their evolution. Density perturbations in an unstable disk grow on a dynamic time scale into spiral arms that produce efficient outward…
Though usually treated in isolation, the magnetorotational and gravitational instabilities (MRI and GI) may coincide at certain radii and evolutionary stages of protoplanetary discs and active galactic nuclei. Their mutual interactions…
We investigate the linear growth and vertical structure of the magnetorotational instability (MRI) in weakly ionised, stratified accretion discs. The magnetic field is initially vertical and dust grains are assumed to have settled towards…
At the time of formation, protoplanetary discs likely contain a comparable mass to their host protostars. As a result, gravitational instabilities (GIs) are expected to play a pivotal role in the early phases of disc evolution. However, as…
Aims. A new mechanism of dust accumulation and planetesimal formation in a gravitationally unstable disk with suppressed magnetorotational instability is studied and compared with the classical dead zone in a layered disk model. Methods. We…
The regions of protoplanetary discs where planets can form are believed to be weakly ionised, suggesting thereby that non-ideal magneto-hydrodynamics (MHD) effects play an important role in the disc dynamics and in the planet formation…
It is likely that young protostellar disks undergo a self-gravitating phase. Such systems are characterized by the presence of a spiral pattern that can be either in a quasi-steady state or in a nonlinear unstable condition. This spiral…
Identifying the mechanisms responsible for angular momentum transport in protoplanetary disks, and the extent to which those mechanisms produce turbulence, is a crucial problem in understanding planet formation. The bulk of the gas in…
Recent observations show that planet formation is already underway in young systems, when the protostar is still embedded into the molecular cloud and the accretion disc is massive. In such environments, the role of self gravity (SG) and…
The discovery of wide-orbit giant exoplanets has posed a challenge to our conventional understanding of planet formation by coagulation of dust grains and planetesimals, and subsequent accretion of protoplanetary disk gas. As an alternative…
Protoplanetary discs are made of gas and dust orbiting a young star. They are also the birth place of planetary systems, which motivates a large amount of observational and theoretical research. In these lecture notes, I present a review of…
To date, most simulations of the chemistry in protoplanetary discs have used 1+1D or 2D axisymmetric $\alpha$-disc models to determine chemical compositions within young systems. This assumption is inappropriate for non-axisymmetric,…