We investigate the time evolution of the six-component electron pressure tensor in a hybrid code studying consequences for the two-dimensional reconnection process in an initially perturbed Harris sheet. We put forward that two tensor components (a diagonal and a non-diagonal one) grow in an unstable way unless an isotropization operator is considered. This isotropization term is physically associated with an electron heat flux. As a consequence, we put forward that an enhanced value of a diagonal component is observed in the very middle of field reversal at sub-ion scale. Because of the increase in the kinetic pressure, the magnetic field is decreased in this electron layer, hence increasing the associated out-of-plane current at its edges and leading to its bifurcation. The bifurcation mechanism is based on the presence of electron pressure anisotropy, related to the gradient of inflow electron bulk velocity. The gradient in the inflow direction of the enhanced diagonal electron pressure tensor component results in the deceleration of the ions entering the X-point region. We suggest that bifurcated current sheets resulting from the anisotropies/agyrotropies of the six-component electron pressure tensor correspond to smaller reconnection rates compared to non-bifurcated ones.

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无碰撞磁重联中非回旋电子压力效应的数值研究

我们研究了混合代码中六分量电子压力张量的时间演化，研究了最初受扰的哈里斯表中二维重联过程的后果。我们提出，除非考虑各向同性算子，否则两个张量分量（对角线和非对角线分量）将以不稳定的方式增长。该各向同性项在物理上与电子热通量相关。因此，我们提出在亚离子尺度的场反转的正中间观察到对角线分量的增强值。由于动压的增加，该电子层中的磁场减小，因此增加了其边缘的相关面外电流并导致其分叉。分叉机制基于电子压力各向异性的存在，与流入电子体积速度的梯度有关。增强的对角电子压力张量分量在流入方向上的梯度导致进入 X 点区域的离子减速。我们建议，与非分叉电流片相比，由六分量电子压力张量的各向异性/自旋向性引起的分叉电流片对应于更小的重新连接率。