空间飞行器近尾区内场的塌缩和密度空洞的形成

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

利用数值模拟计算的方法,研究了运动飞行器与周围等离子体,在近尾区内非稳态非线性相互作用问题,得到了场和密度扰动的分布.结果显示,由于场的塌缩效应,在飞行器的近尾区,形成了可以被探测到的密度空洞和电磁孤波.通过对这种密度空洞和电磁孤波的探测,可以跟踪探测具有隐身特性的飞行器的轨迹.

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, ne = 105/cm3, Te = 3000 K, |E|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.