Effects Of Self-generating Electric Fields In Plasmas On Instabilities Of The Shock Front And Interface

The interaction of a plasma shock with an interface is an important problem in the iner-tial confinement fusion and in astrophysical phenomenon such as supernovae. In this paper,we investigate new effects of a self-generating electric field in a plasma on the instability ofthe shock front and interface in the evaluation of the shock-interface interactions.In this paper, the shock front is treated as a finite thickness region to investigate thestability of the perturbed shock. So, the plasma shock structure is investigated at first.The Rankine-Hugoniot relations of the non-neutral plasma shock are derived, and the two-dimensional axial shock and the one-dimensional strong shock structures are numerical sim-ulated with a set of two-?uids equations and Maxwell equations. With these shock struc-tures, the instability of the perturbed shock front is analyzed in two cases according to theperturbed wavelength. When the wavelength is comparable to the Debye length, an ana-lytic dispersion relation can be obtained through the normal mode analysis and the Fouriertransform in all dimensions. There are instability modes that similar to the Langmiur waveand ionic sound wave in the perturbed shock fronts. The instability is driven by the self-generating electric field and (or) the gradients of the equilibrium parameters in the shockfronts. When the wavelength is comparable to the ion-ion collisional mean free path, theFourier transform is performed only in the dimension, which are perpendicular to the shockpropagation direction. Together with appropriate boundary conditions, a set of differentialequations for the perturbed quantities constitute an eigenvalue problem essentially. Aftersolving the eigenvalue problem, the dispersion relations of the instable modes are plotted.The instability of the perturbed shock front with large wavelength is found to be similar tothe Rayleigh-Taylor instability (RTI).On the other hand of the plasma shock-interface interaction, the evolution of theinterfacial instability, the self-generating field will be emerged also as the plasma describedby the two-?uids equations and Maxwell equations. Taking RTI as an example, the fieldhas stabilized effects on the linear region of the RTI, when the compressibility of the?uid is considered. At the same time, we analyzed the compressibility effects on the RTIsystematically, and concluded new results. The effects of the two parameters representedthe compressibility of the ?uid (the ratio of specific heats and the equilibrium pressure at the interface) on the RTI growth rate are analyzed respectively. When the ratio of specificheats are considered only, the stabilized or destabilized effects on the RTI depend on therelative compressibility of the upper heavy ?uid and lower light ?uid. When the equilibriumpressure at the interface is considered only, the less pressure indicates more compressibilityof the fluid, and larger growth rate. The effects of the equilibrium pressure at the interfaceon the RTI are destabilized.