Magnetic field gradient effects on the magnetorotational instability
arXiv:1705.03473 · doi:10.1002/asna.201713275
Abstract
The magnetorotational instability (MRI), also known as the Balbus -- Hawley instability, is thought to have an important role on the initiation of turbulence and angular momentum transport in accretion discs. In this work, we investigate the effect of the magnetic field gradient in the azimuthal direction on MRI. We solve the magnetohydrodynamic equations by including the azimuthal component of the field gradient. We find the dispersion relation and calculate the growth rates of the instability numerically. The inclusion of the azimuthal magnetic field gradient produces a new unstable region on wavenumber space. It also modifies the growth rate and the wavelength range of the unstable mode: the higher the magnitude of the field gradient, the greater the growth rate and the wider the unstable wavenumber range. Such a gradient in the magnetic field may be important in T Tauri discs where the stellar magnetic field has an axis which is misaligned with respect to the rotation axis of the disc.
8 pages, 3 figures, accepted for publication in AN
References in corpus (8)
- The Magnetic Fields of Classical T Tauri Stars
- Magnetospheric accretion-ejection processes in the classical T Tauri star AA
- Magnetospheric accretion on the T Tauri star BP Tauri
- Hall-effect Controlled Gas Dynamics in Protoplanetary Disks: II. Full 3D Simulations toward the Outer Disk
- T Tauri stellar magnetic fields: He I measurements
- From discs to planetesimals I: evolution of gas and dust discs
- Angular momentum transport in protostellar discs
- MRI: a possible mechanism for funnel flows?