标题： 对等离子体中电子和正电子反向流束的丝状结构的模拟研究 显示英文标题

标题： Simulation study of the filamentation of counter-streaming beams of the electrons and positrons in plasmas

摘要： 由等离子体中两个空间均匀且反向流动的带电粒子束驱动的丝状不稳定性通过粒子-网格（PIC）模拟进行建模。 每个束由电子和正电子组成。 四种粒子种类密度相等，温度相同。 一维模拟方向与束速度矢量垂直。 磁场自发增长并重新排列空间中的粒子，使得一个束的电子分布和第二个束的正电子分布相匹配。 模拟表明，由于磁场在饱和前不会通过其磁压梯度产生静电场。 这种静电场会在丝状结构中心具有排斥性，并限制最大电荷和电流密度。 在此模拟中，电子和正电子的丝状结构达到的电荷和电流密度比没有正电子的情况更高。 由磁约束粒子引起的磁场强度振荡导致振荡的磁压梯度力。 后者与粒子密度的统计涨落相互作用，并可能通过电荷分离强制产生，从而使丝状不稳定性饱和后产生静电波。 显示英文摘要

摘要： The filamentation instability driven by two spatially uniform and counter-streaming beams of charged particles in plasmas is modelled by a particle-in-cell (PIC) simulation. Each beam consists of the electrons and positrons. The four species are equally dense and they have the same temperature. The one-dimensional simulation direction is orthogonal to the beam velocity vector. The magnetic field grows spontaneously and rearranges the particles in space, such that the distributions of the electrons of one beam and the positrons of the second beam match. The simulation demonstrates that as a result no electrostatic field is generated by the magnetic field through its magnetic pressure gradient prior to its saturation. This electrostatic field would be repulsive at the centres of the filaments and limit the maximum charge and current density. The filaments of electrons and positrons in this simulation reach higher charge and current densities than in one with no positrons. The oscillations of the magnetic field strength induced by the magnetically trapped particles result in an oscillatory magnetic pressure gradient force. The latter interplays with the statistical fluctuations in the particle density and it probably enforces a charge separation, by which electrostatic waves grow after the filamentation instability has saturated.