| Research Abstract |
Thermal instability in cooling flows have been studied mainly by linear theory. By previous studies, it is pointed out that gravitational field of cluster of galaxies changes property of linear thermal instability. In order to clarify such effect on the mass deposition in cluster cooling flows, it is needed to study thermal instability in nonlinear stage in 2 or 3 dimension.
In paper 1, we study non-linear perturbation in cluster cooling flow in a simple geometry, that is 2-dimension Cartesian coordinate, by using numerical hydrodynamics. We found that vortices are formed in the perturbation in cooling flows by the effect of gravitational field of cluster of galaxies and can suppress thermal instability of the perturbation. This phenomena is first found by us. We give the criterion that the perturbation cools before the vortex is formed.
In the paper 2, we have adopted rather real situation for geometry of background cooling flow, that is spherical symmetric flow. We show that the formation of vortices and suppression of perturbations by these process actually occur in this case.
In the paper 3, effect of magnetic field on thermal instability is studied by using numerical magneto-hydrodynamics. We have shown weak magnetic field suppress vortex formation and thermal instability is easy to occur by the effect of magnetic field. In this paper, we propose the mass depositon on process is regulated by the magnetic field in cluster of galaxies.
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