ROLES OF VISCOUS MEMBRANE IN AN MHD SELF-ORGANIZATION

In order to examine the role of the energy input in the formation of a n ordered structure in a semi-open system, pie have developed a nonlin ear simulation model in which the energy input time and the dynamic re sponse time of the system are changeable. For this purpose, a viscous membrane (boundary layer) is placed between a steady convection source and a nonlinear feedback system in which a dissipation-free magnetohy drodynamic plasma and a resistive weakly-ionized plasma are coupled. I t is found that the thin viscous membrane acts to be a high-pass filte r that can play a role of a fixed boundary for the dc component but a free boundary for the ac component. Because of this character of the m embrane, when the ratio of the ac energy input time to the dynamic res ponse lime of the system becomes relatively large, the membrane acts t o release the fluctuation (ac) energy from the system. Consequently, t he positive feedback effect for the fluctuation is weakened and the st ructure formation is prevented as the ratio exceeds a certain critical value. It is also found that the viscous membrane plays another impor tant more in self-organization: namely, that as the structure formatio n is highly progressed, the dc energy input rate is autonomously adjus ted so as to keep the developed structure in a steady form.