THE COLLAPSES OF ELECTRIC FIELD AND FORMATION OF DENSITY CAVITONS IN THE WAKE OF MOVING BODY IN SPACE

In this paper, using the method of numerical simulation, the nonsteady and nonlinear interaction between the moving body and plasma in wake region was studied in detail. Starting from the two fluid equations and the collisionless Boltz-mann equation for the ion distribution, under the condition of a static limit, for the low-frequency disturbance, the nonlinear coupling equations have been obtained. In order to get the value of Δn, the fast Fourier translation has been used and the initial condition of wavepacket form that the envelope is slowly varying function over time has been chosen in Cartesian coordinates system. For the purpose of easy to calculation the initial condition has the form of two dimensions with three field components. The results of whole wake region can be obtained by rotating the results in a two dimensional space. Of course, the choice of initial condition is not unique. In the simulation, the natural boundary conditions in x direction i.e. the field quantities are zero when x →∞, and a periodic boundary conditions in z direction have been used. The method of numerical simulation is FTCS (time forward-difference and space central-difference method). Finally the distributions of the electromagnetic soliton and density disturbance have been obtained. The basic parameters in calculation are v₀ = 10⁶ cm/s, R₀ = 100cm, n_e = 10⁵/cm³, T_e = 3000 K, |Ê|_max²(τ= 0) = 2.42. The results show that in the wake region of the moving body, there are the formation of the electromagnetic soliton and density disturbance which can be detected due to the collapse of electric field. As the field and density increasing, the condition W < 1 is not valid, the numerical simulation has to stop. We can trace out the moving body by means of observing the structure and intensity of the density caviton and electromagnetic soliton although the body may be a stealthy vehicle.