排序方式: 共有17条查询结果,搜索用时 15 毫秒
1.
One-dimensional particle-in-cell simulations are performed to investigate the nonlinear evolution of electromagnetic instabilities excited by the electron temperature anisotropy in homogeneous plasmas with different parameters. The results show that the electron temperature anisotropy can excite the two right-hand electromagnetic instabilities, one has the frequency higher than Ωe, the other is the whistler instability with larger amplitude, and its frequency is below Ωe. Their dispersion relations are consistent with the prediction from the cold plasma theory. In the initial growth stage (prediction from linear theory), the frequency of the dominant mode (the mode whose amplitude is large enough) of the whistler wave almost does not change, but in the saturation stage the situation is different. In the case that the ratio of electron plasma frequency to cyclotron frequency is larger than 1, the frequency of the dominant mode of the whistler wave driRs from high to low continuously. However, for the case of the ratio smaller than 1, besides the original dominant mode of the whistler wave whose frequency is about 2.6ωe, another dominant mode whose frequency is about 1.55ωe also begins to be excited at definite time, and its amplitude increases with time until it exceeds the original dominant mode. 相似文献
2.
超短超强激光与稀薄等离子体相互作用的数值研究 总被引:2,自引:0,他引:2
用一维粒子模拟方法(Particle-in-Cell)数值研究了超短超强激光(Iλ^2〉10^18W.μm^2/cm^2)与稀薄等离子体的相互作用过程,结果表明,超短超强激光与稀薄等相互作用后,在等离子体中激发起尾波和拉曼(Raman)波,它们的波长和频率的值与解析解符合得很好;同时在尾波的作用下,等离子体的部分电子被加速的很高的速度,甚至接近光速。 相似文献
3.
Effects of Perpendicular Thermal Velocities on the Transverse Instability in Electron Phase Space Holes 总被引:1,自引:0,他引:1 下载免费PDF全文
A multi-dimensional electron phase-space hole (electron hole) is considered to be unstable to the transverse instability. We perform two-dimensional (2D) particle-in-cell (PIC) simulations to study the evolutions of electron holes in weakly magnetized plasma (Ωe〈 Wpe, where Ωe and Wpe are the electron gyrofrequency and plasma frequency, respectively), and the effects of perpendicular thermal velocities on the transverse instability are investigated. The transverse instability can cause decay of the electron holes. We find that with the increasing perpendicular thermal velocity tending to stabilize the transverse instability, the corresponding wave numbers decrease. 相似文献
4.
<正>Ion pickup by a monochromatic low-frequency Alfven wave,which propagates along the background magnetic field,has recently been investigated in a low beta plasma(Lu and Li 2007 Phys.Plasmas 14 042303).In this paper, the monochromatic Alfven wave is generalized to a spectrum of Alfven waves with random phase.It finds that the process of ion pickup can be divided into two stages.First,ions are picked up in the transverse direction,and then phase difference(randomization) between ions due to their different parallel thermal motions leads to heating of the ions.The heating is dominant in the direction perpendicular to the background magnetic field.The temperatures of the ions at the asymptotic stage do not depend on individual waves in the spectrum,but are determined by the total amplitude of the waves.The effect of the initial ion bulk flow in the parallel direction on the heating is also considered in this paper. 相似文献
5.
A 21/2-dimensional electromagnetic particle-in-cell (PIC) simulation code is used to investigate the electron acceleration in collisionless magnetic reconnection. The results show that the electrons are accelerated in the diffusion region near the X point, and the acceleration process can be roughly divided into two procedures: firstly the electrons are accelerated in the z direction due to the electric field in the negative z direction. Then the electrons gyrate surrounding the magnetic field with the action of the Lorentz force, through this procedure the electrons reach higher velocity in the x direction and then flow out of the diffusion region. After being accelerated away from the diffusion region, part of electrons is trapped near the O point, and the other part of electrons flows into plasma sheet boundary layer along the magnetic field. 相似文献
6.
通过区域分解法实现了二维等离子体粒子模拟程序并行化,并将此程序运行在由16个PentiumⅢ1 6GCPU组成的微机机群上,对其性能进行了测试.结果表明,在计算规模一定的情况下,并行程序的并行效率随计算结点的增加而降低;而在计算节点不变的情况下,并行效率随计算规模的增加而增加,并行计算更适合于计算规模大的物理问题.利用此并行程序计算了等离子体中的束流不稳定性,结果表明,在波动激发的线性增长阶段,等离子体束流激发的Alfv啨n波基本上沿背景磁场方向传播,其波数满足共振条件ω-kVb=-Ωi,其中ω和k分别为Alfv啨n波的频率和波数,Vb为束流的速度,Ωi为离子的回旋频率. 相似文献
7.
超短超强激光和稠密等离子体相互作用的数值研究 总被引:1,自引:0,他引:1
应用一维粒子模拟方法数值研究了超短超中激光和稠密等离子体的相互作用,结果表明,在等离子体中的激发起无规则的电场波动,同时在等离子体中产生温度很高的电子。 相似文献
8.
Previous particle-in-cell simulations have evidenced that supercritical, quasi-perpendicular shocks are non-stationary. By separating the incident ions into reflected (R) and directly transmitted (DT) parts, we investigate the ion distributions in a non-stationary perpendicular shock. The upstream ion distributions have two parts corresponding to the R and incident ions respectively, while the R ions have higher energy. The downstream ions have a core-ring distribution. The core and ring parts correspond to the DT and R ions, respectively. The ion distributions depend largely on the non-stationary shock structure. The percentage of the reflected ions cyclically varies in time with a period equal to the shock self-reformation cycle, and the number of the R ions increases with the steepness of the shock ramp. 相似文献
9.
Ion pickup by a monochromatic low-frequency Alfvén wave, which
propagates along the background magnetic field, has recently been
investigated in a low beta plasma (Lu and Li 2007 Phys.
Plasmas 14 042303). In this paper, the monochromatic Alfvén
wave is generalized to a spectrum of Alfvén waves with random
phase. It finds that the process of ion pickup can be divided into
two stages. First, ions are picked up in the transverse direction,
and then phase difference (randomization) between ions due to their
different parallel thermal motions leads to heating of the ions. The
heating is dominant in the direction perpendicular to the background
magnetic field. The temperatures of the ions at the asymptotic stage do
not depend on individual waves in the spectrum, but are determined
by the total amplitude of the waves. The effect of the initial ion
bulk flow in the parallel direction on the heating is also
considered in this paper. 相似文献
10.
二维混合模拟方法及应用 总被引:1,自引:1,他引:0
设计了一个二维混合模拟程序,并用其计算了等离子体物理中的束流不稳定性,结果表明,此程序在计算过程中使能量基本保持守恒,计算结果同理论分析及一维混合模拟结果相一致。 相似文献