language: en

The Effects of Collisions with Neutral Particles on the InstabiUty of Two Superposed Composite Plasmas Streaming Through Porous Medium

Mohamed Fahmy El-Sayed
Department of Mathematics and Computer Science, Faculty of Science,
United Arab Emirates University, R O. Box 17551 Al Ain, U. A. E.
Also at: Department of Madiematics, Faculty of Education, Ain Shams University,
Roxy, Cairo, Egypt

[Reprint requests to Dr. M, R El-Sayed]

; E-mail; elsayed@nyx.uaeu.ac.ae Z. Naturforsch. 54 a, 411^16 (1999);

[received April 19, 1999]

The effects of collisions widi neutral atoms on die hydromagnetic stability of the plane interface separating two streaming superposed composite plasmas of uniform densities in a porous medium are investigated. In die absence of fluid velocities, it is found, for a potentially stable configuration, that die system remains stable, while for a potentially unstable configuraion, the unstable system becomes stable under a certain condition of die wavenumber depending on the values of thc fluid densities, Alfven velocities, and die orientation of die magnetic field. The porosity of die porous medium does not have any significant effect on die stability criterion. In the presence of fluid velocities, it is found that, the instability criterion is independent of the permeability of die medium and die collision effects widi neutral particles. The criterion determing die stability does not depend on the permeability of the medium but depends on die density of neutral particles. The porosity of the medium is found to have a significant effect on bodi the stability and instability criteria in this case. The role of die permeability of the medium, die collisional frequency, and the porosity of die porous medium on the growth rate of the unstable mode is examined analitically. Routh's test of stability is applied to confirm the above results.

PACS: 47.20,-k; 47.55.Mh; 47.65.+a; 52.30.-q; 52.35.-g. Key words: HydTodynzmic Stability; Flows dirough Porous Media; Magnetohydrodynamics; Plasma flow; Instabilities in Plasma.

Introduction