有质动力和静电分离场对激光等离子体流体力学状态的影响

利用建立在欧拉坐标系上的一维电子_离子双流双温流体力学程序, 模拟了超短脉冲强激光 (1×1015W/cm2, 150fs)与线性密度梯度等离子体相互作用的流体力学过程. 模拟结果显示，入射激光与临界密度面的反射光叠加，在临界密度以下区域形成局域驻波， 产生的强有质动力在低密区驱动电子形成周期性密度结构——Bragg光栅，激光的反射被增 强. 临界密度处有质动力将等离子体分成向内和向外运动的两部分. 由于离子所受的有质动 力和热压强的梯度力远小于电子，体系产生了强静电分离场，离子的运动主要由该静电分离 场决定. 对双流双温模型和单流双温模型的模拟结果进行了比较. 当有质动力和热压强梯度 力较大时，两种模型对等离子体流体力学状态的描述有明显差异，单流双温模型无法描述此 时的流体力学状态. 关键词： 有质动力 密度调制 双流双温流体力学模型 单流模型

Effects of ponderomotive forces and space-charge field on laser plasma hydrodynamics

Using a two_fluid two_temperature hydrodynamic code, we studied the hydrodynamic s in the interaction of intense (1015W/cm2) ultrashort (150fs) laser pulses and linear density plasmas. The simulation results show the ponderomotiv e force effect on the formation of the electron density ripples in underdense re gion, such ripples increase the reflection of the laser pulse, and on the separa tion of the plasma in critical surface. Quasi_electroneutrality is not suitable in this case because of the different ponderomotive force and the gradient of th ermal_pressure for ions and electrons. Ions are moved by the electrostatic force . Comparing with the simulation results from one_fluid two_temperature code, we find that under strong ponderomotive force and gradient of thermo_pressure, two_ fluid code is more suitable to simulate the hydrodynamics of plasmas.