2015/10/09 by Gopakumar Mohandas, Mohandas, Gopakumar, Martín E. Pessah +2
Chemistry · Physics and Astronomy · #Adiabatic process #Astro and Planetary Science #Astrophysics and Star Formation Studies #Classical mechanics #Convection #Convection zone #Earth and Planetary Astrophysics (astro-ph.EP) #FOS: Physical sciences #Inertial frame of reference #Instability #Magnetic field #Magnetohydrodynamics #Mechanics #Molecular Spectroscopy and Structure #Physics #Plasma #Rotational symmetry #Shear (geology) #Stellar, planetary, and galactic studies #Tachocline #Toroid #astro-ph.EP
paper · pdf · doi:10.48550/arxiv.1510.02729
published in arXiv (Cornell University) (Cornell University) · submitted to ApJ
arxiv created 2015/10/09 · openalex publication_date 2015/10/09 · arxiv updated 2015/10/12 · openalex created_date 2022/09/03 · openalex updated_date 2026/08/05
We conduct a comprehensive axisymmetric, local linear mode analysis of a\nstratified, differentially rotating disk permeated by a toroidal magnetic field\nwhich could provide significant pressure support. In the adiabatic limit, we\nderive a new stability criteria that differs from the one obtained for weak\nmagnetic fields with a poloidal component and reduces continuously to the\nhydrodynamic Solberg-H oiland criteria. Three fundamental unstable modes are\nfound in the locally isothermal limit. They comprise of overstable: (i)\nacoustic oscillations, (ii) radial epicyclic (acoustic-inertial) oscillations\nand (iii) vertical epicyclic (or vertical shear) oscillations. All three modes\nare present for finite ranges of cooling times but they are each quickly\nquenched past respective cut-off times. The acoustic and acoustic-inertial\noverstable modes are driven by the background temperature gradient. When\nvertical structure is excluded, we find that the radial epicyclic modes appear\nas a nearly degenerate pair. One of these is the aforementioned\nacoustic-inertial mode and the other has been previously identified in a\nslightly different guise as the convective overstability. Inclusion of vertical\nstructure leads to the development of overstable oscillations destabilized by\nvertical shear but also has the effect of suppressing the radial epicyclic\nmodes. Although our study does not explicitly account for non-ideal effects, we\nargue that it may still shed light into the dynamics of protoplanetary disk\nregions where a strong toroidal field generates as a result of the Hall-shear\ninstability.\n