Drift turbulence, particle transport, and anomalous dissipation at the reconnecting magnetopause
Drift turbulence, particle transport, and anomalous dissipation at the reconnecting magnetopause
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DOI：
10.1063/1.5027086
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发表时间：
2018-06-01
影响因子：
2.2
通讯作者：
Bird, R.
中科院分区：
文献类型：
--
作者：
Le, A.;Daughton, W.;Bird, R.
利用全动力学三维模拟，研究了地球磁层顶不对称电流片的重联动力学。选择等离子体参数来模拟MMS磁层顶扩散区交叉，导向场为重新连接的磁鞘磁场的0.1、0.4和1。在每一种情况下，在磁层分离线上密度梯度较大的低混合频率范围内都观察到了强烈的漂移波波动。这些涨落引起了跨场电子粒子输运。此外，与2D模拟相比，这种湍流混合导致电子平行加热显著增强。我们研究了三种不同的量化漂移涨落产生的反常耗散的方法，即基于空间平均、时间平均和时间平均然后沿磁场线积分的方法。不同方法的比较揭示了识别和测量异常耗散的复杂性。然而，短波漂移涨落的反常耗散在每种情况下都显得很弱，并且在3D模型中观察到的重联率与在2D模型中观察到的重联率几乎相同。3D模拟具有许多有趣的新特征，这些特征与最近的MMS观测一致，包括穿透到更热的磁层流入的磁鞘电子的冷束，总密度增加区域的相关观测到的温度下降，以及与准线性理论预测一致的有效湍流扩散系数。由AIP出版公司出版。
Using fully kinetic 3D simulations, the reconnection dynamics of asymmetric current sheets are examined at the Earth's magnetopause. The plasma parameters are selected to model MMS magnetopause diffusion region crossings with guide fields of 0.1, 0.4, and 1 of the reconnecting magnetosheath field. In each case, strong drift-wave fluctuations are observed in the lower-hybrid frequency range at the steep density gradient across the magnetospheric separatrix. These fluctuations give rise to cross-field electron particle transport. In addition, this turbulent mixing leads to significantly enhanced electron parallel heating in comparison to 2D simulations. We study three different methods of quantifying the anomalous dissipation produced by the drift fluctuations, based on spatial averaging, temporal averaging, and temporal averaging followed by integrating along magnetic field lines. A comparison of different methods reveals complications in identifying and measuring the anomalous dissipation. Nevertheless, the anomalous dissipation from short wavelength drift fluctuations appears weak for each case, and the reconnection rates observed in 3D are nearly the same as in 2D models. The 3D simulations feature a number of interesting new features that are consistent with recent MMS observations, including cold beams of magnetosheath electrons that penetrate into the hotter magnetospheric inflow, the related observation of decreasing temperature in regions of increasing total density, and an effective turbulent diffusion coefficient that agrees with predictions from quasi-linear theory. Published by AIP Publishing.