ParkerJeans Instability of Gaseous Disks
Abstract
The magnetohydrodynamical instability of selfgravitating magnetized gaseous disks is investigated by means of a normalmode analysis. The growth rates and eigenfunctions of unstable perturbations are obtained numerically. The perturbed disks are shown graphically. Selfgravitating magnetized gaseous disks, in general, suffer from two kinds of instabilities, the Jeans and Parker types. The former is driven by selfgravity and the latter by a nonuniform magnetic field. These two kinds of instabilities coexist in our model and have different characteristics. In our equilibrium model disk, the Jeans mode has a larger growth rate than does the Parker mode, when either the magnetic field is weak or the wavelength of the perturbation is long. The Parker instability dominates when the magnetic field is strong and the wavelength is short. The Jeans instability disturbs mainly the highdensity region near the midplane; the Parker instability disturbs mainly the lowdensity region far from the midplane. The growth rate of the Jeans instability is maximum when the wave vector of the perturbation is parallel to the magnetic field. On the other hand, that of the Parker instability is maximum when the wavenumber in the direction perpendicular to the magnetic field is infinitely large.
 Publication:

Publications of the Astronomical Society of Japan
 Pub Date:
 October 1991
 Bibcode:
 1991PASJ...43..685N
 Keywords:

 Computational Astrophysics;
 Gravitational Effects;
 Interstellar Gas;
 Jeans Theory;
 Magnetohydrodynamic Stability;
 Molecular Clouds;
 Asymptotic Methods;
 Equilibrium Equations;
 Galactic Structure;
 Interstellar Magnetic Fields;
 Star Formation;
 Astrophysics;
 FRAGMENTATION;
 GRAVITATIONAL INSTABILITY;
 MAGNETOHYDRODYNAMICAL INSTABILITY