دکتر محمدعلی معصوم پرست کتک لاهیجانی

In this research, the effect of simultaneous application of plasma rotation and static external magnetic field in a plasma with power law density function on the growth rate of Rayleigh-Taylor instability has been studied analytically. The plasma is assumed to be an incompressible and is enclosed between two planes z=0 and z=h. In a linear growth rate regime, the dispersion relation for the ideal MHD equations was first derived by applying the rotation effect and appropriate boundary conditions. The final dispersion relation represents the effect of the simultaneous combination of the axial magnetic field and the constant angular velocity of the plasma on the growth rate of Rayleigh-Taylor instability. The results show that the growth rate of the instability depends on the horizontal component of the magnetic field, the plasma rotation and also the dimensionless parameter λ*. The maximum instability occurs at the value of λ*=-1.5. Compared to the corresponding non-rotational case, recent results show that the simultaneous combination of rotation and static external magnetic field improves the management of the instability growth rate.

The use of the initial power density gradient in the plasma makes disorder growth relatively slow and invisible. In fact, the power density reduces the disorder growth rate during the acceleration phase. By choosing a power density greater than 2 for the power density, the density changes decrease rapidly with increasing aspect ratio near the stagnation moment. For n=3 the disturbance amplitude is reduced by five times compared to the uniform state. In this research, the power density gradient along with the effect of static external magnetic field on the growth rate of Rayleigh-Taylor instability in non-uniform incompressible plasma confined between two planes z=0 and z=h has been analyzed analytically. The problem dispersion relation was derived by linearizing the MHD equations and applying appropriate boundary conditions. The results show that the growth rate of instability depends on the horizontal and vertical components of the magnetic field as well as the dimensionless parameter λ* (= -1.5, -0.5, 1), and the maximum instability occurs at λ*= -1.5. In order to manage the growth rate of instability, it is observed that the simultaneous combination of horizontal and vertical magnetic fields provides faster stability for the system. With the increase in the intensity of the static external magnetic field, the square amplitude of the instability growth rate decreases by about 15% and the critical point decreases by 58%. This decreasing process is very slow compared to the results obtained from the apparent density. Therefore, as expected, using the factor of 3 for the initial power density of the plasma causes a slight decrease in the growth rate of the disorder. This confirms the correctness of the calculations and the obtained results.