磁场重联中的哨声波与Hall效应

数值研究Hall电流效应对于重联动力学特征及波动特性的影响.结果表明,具有强Hall效应的算例,重联出流区张角大,重联率高.对于不同Hall效应的算例,应用快速傅里叶变换(FFT),将平面外磁场By分量和(x,z)平面内的速度分量vx,vz位于给定点的时间序列转换为功率谱,并对电场E采用最小方差分析法,确定波的传播方向与偏振特性.研究发现,在强Hall效应的算例中,磁分界线附近存在具有典型特征的哨声波,Hall效应减弱,则波动信号减弱.上述结果表明,Hall电流效应对重联动力学特征具有重要影响,是产生哨声波和快速重联率的关键因素;此外,对于强Hall效应的算例,磁分界线附近哨声波幅度与平面内场向电流Jp间存在正相关关系,它从另一个侧面展示了哨声波与Hall效应间的重要联系. 

Whistler Wave and Hall Effect in Magnetic Reconnection

The effects of Hall current on the reconnection dynamics and wave behavior are numerically studied in this report. The notable reductions in the openness of outflow region and the reconnection rate are shown as Hall effect weakens. The time series of the out-of-plane magnetic field By and the velocity components vx,vz in the (x,z) plane at the given points are transferred into the power spectra by the Fast Fourier Transformation (FFT) for the cases with various intensive Hall terms. Using the Minimum Variance Analysis (MVA) on E, the propagation directions and the polarized features of waves are determined. It can be found that there exists the whistler wave with the typical features near the magnetic separatrices in the case of the stronger Hall effect and the wave signature weakens substantially as the intensity of Hall effect is reduced. These results indicate that Hall effect has an important influence on the reconnection dynamics and plays a crucial role in generating the whistler-mode wave and fast reconnection rate. Besides, there is a positive coherency between the amplitude of whistler wave and the field-aligned current Jp in the plane near the magnetic separatrices in the case with the strong Hall term. It demonstrates the closed linkage between the whistler wave and Hall effect on the other hand.