磁重联电流片的参数变化对电子加速的影响

Impact of Variations of the Parameters for the Current Sheet on Electron Accelerations

通过采用试验粒子的方法,研究了在有引导磁场B_z存在的磁重联电流片中,电子被super-Dreicer电场E_z加速后的运动特征。首先,考虑了引导磁场恒定且与电场有不同方向时对粒子加速的影响。在这种情况下,B_z方向的改变直接改变了电子的运动轨迹,使其沿着不同的路径离开电流片。在B_z和E_z同向时,高能电子的pitch-angle接近于180°。然而,当2者反向时,高能电子的pitch-angle接近0°。引导磁场的取向只是使电场有选择地对不同区域的电子进行加速,不会最终影响电子的能量分布,最终得到的能谱是普遍的幂率谱E^(-γ)。在典型的日冕条件下,γ大约等于2.9。进一步的研究表明γ的大小依赖于引导磁场及磁重联电场的强弱,以及电流片的尺度。随后,也研究了包含多个X-点和O-点电流片中被加速粒子的运动特征。结果表明X-点和O-点的存在使得粒子被束缚在加速区并获得最大的加速,而且最终的能谱具有多幂率谱的特征。

The kinematic characteristic of electrons after acceleration by a super-Dreicer electric field Ez is investigated in the reconnecting current sheet （RCS） with a guiding magnetic field Bz by simulations of testing particles. Firstly, the influence of the different directions of the electric filed on the acceleration of particles, changing the trajectories of electrons, is discussed when assuming the magnetic field as a constant. If Bz parallels to Ez, the pitch-angle of accelerated electrons is close to 180°; If Bz anti-parallels to Ez, the pitch-angle is close to 0°. The different directions of the guiding magnetic field lead to different regions where electrons are accelerated by the electric field but will not change the final energy distribution of electrons-in form of a power-law distribution E^-γ. γ approximates to 2.9 in typical coronal conditions. Further research indicates that 7 depends on the strength of both the guiding field and electric field and the scale of the current sheet. Secondly, the kinematic characteristic of accelerated particles in the current sheet including multiple X- and O-points is further investigated. Particles in the RCS with X- and O- points are trapped and get the maximal acceleration in the accelerating region. The final energy spectrum shows a multiple power-law distribution.