Publication Date:
2015-03-25
Description:
This paper analyzes the coupling of magneto-Rayleigh-Taylor (MRT), sausage, and kink modes in an imploding cylindrical liner, using ideal MHD. A uniform axial magnetic field of arbitrary value is included in each region: liner, its interior, and its exterior. The dispersion relation is solved exactly, for arbitrary radial acceleration (- g ), axial wavenumber ( k ), azimuthal mode number ( m ), liner aspect ratio, and equilibrium quantities in each region. For small k , a positive g (inward radial acceleration in the lab frame) tends to stabilize the sausage mode, but destabilize the kink mode. For large k , a positive g destabilizes both the kink and sausage mode. Using the 1D-HYDRA simulation results for an equilibrium model that includes a pre-existing axial magnetic field and a preheated fuel, we identify several stages of MRT-sausage-kink mode evolution. We find that the m = 1 kink-MRT mode has a higher growth rate at the initial stage and stagnation stage of the implosion, and that the m = 0 sausage-MRT mode dominates at the main part of implosion. This analysis also sheds light on a puzzling feature in Harris' classic paper of MRT [E. G. Harris, Phys. Fluids 5 , 1057 (1962)]. An attempt is made to interpret the persistence of the observed helical structures [Awe et al. , Phys. Rev. Lett. 111 , 235005 (2013)] in terms of non-axisymmetric eigenmode.
Print ISSN:
1070-664X
Electronic ISSN:
1089-7674
Topics:
Physics
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