【摘要】 数值研究具有不同等离子体β值(等离子体热压与磁压之比)的Hall MHD重联过程．对于β值在0．5≤β≤6．5的算例,稳态重联率(?)A／(?)t|st为0．15≥(?)A／(?)t|st≥0．095．本文研究β值在上述范围内的Hall MHD重联中的波动．通过快速傅里叶变换(FFT),将平面外磁场By分量和xz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．结果表明,By,vx,vz功率谱的频率范围为Ωci<ω<8Ωci,其中Ωci为离子回旋频率．随着β值增大,功率谱峰值能量降低,并且朝着低频端移动．对于电场E采用最小方差分析法(MVA)可以确定波的传播方向k,波矢k与局地磁场B之间的夹角α随β值增大而增大．对于β值最大的算例3(β=6．5),α<28°．上述结果表明,k准平行于B．为了研究波的偏振特征,在垂直于k的平面内画出E的矢端图．三个算例的矢端图均表明,波动具有右旋偏振特征,在算例1(β=0．5)中矢端图为右旋椭圆偏振,而在算例2(β=2．5)和算例3(β=6．5)中矢端图变成复杂的右旋偏振图形,这些均为哨声波的典型特征．本文的研究为快速磁重联与哨声波之间提供了一种可能的联系．更多还原

【Abstract】 The Hall MHD recormection processes with various plasmaβ(the ratio of plasma pressure to the magnetic pressure) are numerically studied. The reconnection rate (?)A/(?)t|st at the quasi-steady state is in the range of 0.15≥(?)A/(?)t|st≥0.095 for the cases with plasmaβranging 0.5≤β≤6.5. In this report, the waves in the Hall MHD reconnection are investigated: The time series of the out-of-plane magnetic field By and the velocity components vx,vz in the xz plane at the given points are transferred into the power spectra by the Fast Fourier Transformation (FFT) for the cases with various plasmaβ. The results indicate that the frequencies of the By,vx,vz power spectra are in the range ofΩci <ω< 8Ωci whereΩci is the proton cyclotron frequency. A shift to low frequency and the energy reduction at the peaks in the power spectrum can be found as the plasmaβincreases. Using the Minimum Variance Analysis (MVA) on E, the. propagation directions k of the waves are determined. The anglesαbetween the wave vector k and the local magnetic field B increase with increasingβ: For case 3 with the largest (β= 6.5)α< 28°, so that k is approximately parallel to B. In order to investigate the polarized features of waves the hodographs of E are plotted in the plane perpendicular to the wave vector k. The hodographs for all three cases illustrate a right-hand circularly polarized feature. In case 1 withβ=0.5, it is a right-hand elliptical polarization, but in case 2 (β= 2.5) and case 3 (β= 6.5) the hodographs become a complicated right-hand circulation. Such wave behaviors are the signatures of whistler wave, and so the present work might provide a link between the fast reconnection rate and whistler wave.更多还原