We present 2D , ideal–MHD numerical simulations of the Parker instability in a multi–component warm disk model .
The calculations were done using two numerical codes with different algorithms , TVD and ZEUS-3D .
The outcome of the numerical experiments performed with both codes is very similar , and confirms the results of the linear analysis for the undular mode derived by Kim et al .
( 2000 ) : the most unstable wavelength is about 3 kpc and its growth timescale is between 30–50 Myr ( the growth rate is sensitive to the position of the upper boundary of the numerical grid ) .
Thus , the time and length scales of this multicomponent disk model are substantially larger than those derived for thin disk models .
We use three different types of perturbations , random , symmetric , and antisymmetric , to trigger the instability .
The antisymmetric mode is dominant , and determines the minimum time for the onset of the nonlinear regime .
The instability generates dense condensations and the final peak column density value in the antisymmetric case , as also derived by Kim et al .
( 2000 ) , is about a factor of 3 larger than its initial value .
These wavelengths and density enhancement factors indicate that the instability alone can not be the main formation mechanism of giant molecular clouds in the general interstellar medium .
The role of the instability in the formation of large-scale corrugations along spiral arms is briefly discussed .