Magnetohydrodynamics of protoplanetary discs
arXiv:2007.15967
Abstract
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 the magnetic mechanisms applied to the outer regions R>1 AU of these discs, which are the planet-formation regions. In contrast to usual astrophysical plasmas, the gas in these regions is noticeably cold (T<300 K) and dense, which implies a very low ionisation fraction close to the disc midplane. In these notes, I deliberately ignore the innermost R~0.1 AU region which is influenced by the star-disk interaction and various radiative effects. I start by presenting a short overview of the observational evidence for the dynamics of these objects. I then introduce the methods and approximations used to model these plasmas, including non-ideal MHD, and the uncertainties associated with this approach. In this framework, I explain how the global dynamics of these discs is modelled, and I present a stability analysis of this plasma in the local approximation, introducing the non-ideal magneto-rotational instability. Following this mostly analytical part, I discuss numerical models which have been used to describe the saturation mechanisms of this instability, and the formation of large-scale structures by various saturation mechanisms. Finally, I show that local numerical models are insufficient since magnetised winds are also emitted from the surface of these objects. After a short introduction on winds physics, I present global models of protoplanetary discs, including both a large-scale wind and the non-ideal dynamics of the disc.
115 pages, 46 figures, accepted for publication in the lecture notes series of the Journal of Plasma Physics (Cambridge University Press)
References in corpus (20)
- Protoplanetary Disk Structures in Ophiuchus
- Spiral Density Waves in a Young Protoplanetary Disk
- Global simulations of protoplanetary disks with ohmic resistivity and ambipolar diffusion
- Impact of dimensionless numbers on the efficiency of MRI-induced turbulent transport
- Constraining the X-ray and Cosmic Ray Ionization Chemistry of the TW Hya Protoplanetary Disk: Evidence for a Sub-interstellar Cosmic Ray Rate
- Meridional flows in the disk around a young star
- Hall-effect Controlled Gas Dynamics in Protoplanetary Disks: II. Full 3D Simulations toward the Outer Disk
- Heat and Dust in Active Layers of Protostellar Disks
- Mapping accretion and its variability in the young open cluster NGC 2264: a study based on u-band photometry
- Magnetic Flux Concentration and Zonal Flows in Magnetorotational Instability Turbulence
- Spatially Resolved Magnetic Field Structure in the Disk of a T Tauri Star
- ALMA Reveals Transition of Polarization Pattern with Wavelength in HL Tau's Disk
- Helical Magnetorotational Instability in Magnetized Taylor-Couette Flow
- On Self-Sustained Dynamo Cycles in Accretion Discs
- Magnetically-driven jets and winds from weakly magnetized accretion disks
- Dissipative effects on the sustainment of a magnetorotational dynamo in Keplerian shear flow
- Shearing box simulations of accretion disk winds
- Multifluid simulations of the Magnetorotational Instability in protostellar disks
- Local semi-analytic models of magnetic flux transport in protoplanetary discs
- Global multifluid simulations of the magnetorotational instability in radially stratified protoplanetary disks