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arXiv · 0708.3753

Transient growth and coupling of vortex and wave modes in self-gravitating gaseous discs

G. R. Mamatsashvili·G. D. Chagelishvili
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Abstract

Flow nonnormality induced linear transient phenomena in thin self-gravitating astrophysical discs are studied in the shearing sheet approximation. The considered system includes two modes of perturbations: vortex and (spiral density) wave. It is shown that self-gravity considerably alters the vortex mode dynamics -- its transient (swing) growth may be several orders of magnitude stronger than in the non-self-gravitating case and 2-3 times larger than the transient growth of the wave mode. Based on this finding, we comment on the role of vortex mode perturbations in a gravitoturbulent state. Also described is the linear coupling of the perturbation modes, caused by the differential character of disc rotation. The coupling is asymmetric -- vortex mode perturbations are able to excite wave mode ones, but not vice versa. This asymmetric coupling lends additional significance to the vortex mode as a participant in spiral density waves and shocks manifestations in astrophysical discs.

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G. R. Mamatsashvili, G. D. Chagelishvili. 2007-08-28. Transient growth and coupling of vortex and wave modes in self-gravitating gaseous discs. https://doi.org/10.1111/j.1365-2966.2007.12274.x

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