Hasegawa H, Nakamura T K M, Denton R E
Institute of Space and Astronautical Science Japan Aerospace Exploration Agency Sagamihara Japan.
Institute of Physics University of Graz Graz Austria.
J Geophys Res Space Phys. 2021 Nov;126(11):e2021JA029841. doi: 10.1029/2021JA029841. Epub 2021 Nov 17.
A method based on electron magnetohydrodynamics (EMHD) for the reconstruction of steady, two-dimensional plasma and magnetic field structures from data taken by a single spacecraft, first developed by Sonnerup et al. (2016), https://doi.org/10.1002/2016ja022430, is extended to accommodate inhomogeneity of the electron density and temperature, electron inertia effects, and guide magnetic field in and around the electron diffusion region (EDR), the central part of the magnetic reconnection region. The new method assumes that the electron density and temperature are constant along, but may vary across, the magnetic field lines. We present two models for the reconstruction of electron streamlines, one of which is not constrained by any specific formula for the electron pressure tensor term in the generalized Ohm's law that is responsible for electron unmagnetization in the EDR, and the other is a modification of the original model to include the inertia and compressibility effects. Benchmark tests using data from fully kinetic simulations show that our new method is applicable to both antiparallel and guide-field (component) reconnection, and the electron velocity field can be better reconstructed by including the inertia effects. The new EMHD reconstruction technique has been applied to an EDR of magnetotail reconnection encountered by the Magnetospheric Multiscale spacecraft on 11 July 2017, reported by Torbert et al. (2018), https://doi.org/10.1126/science.aat2998 and reconstructed with the original inertia-less version by Hasegawa et al. (2019), https://doi.org/10.1029/2018ja026051, which demonstrates that the new method better performs in recovering the electric field and electron streamlines than the original version.
一种基于电子磁流体动力学（EMHD）的方法，用于从单个航天器获取的数据重建稳态二维等离子体和磁场结构，该方法最初由索内鲁普等人（2016年）开发，https://doi.org/10.1002/2016ja022430，现进行了扩展，以适应电子密度和温度的不均匀性、电子惯性效应以及电子扩散区域（EDR）（磁重联区域的中心部分）及其周围的引导磁场。新方法假设电子密度和温度沿磁力线方向不变，但在垂直于磁力线方向上可能变化。我们提出了两种用于重建电子流线的模型，其中一种不受广义欧姆定律中负责EDR内电子去磁化的电子压力张量项的任何特定公式的约束，另一种是对原始模型的修改，以纳入惯性和可压缩性效应。使用全动力学模拟数据进行的基准测试表明，我们的新方法适用于反平行重联和引导场（分量）重联，并且通过纳入惯性效应可以更好地重建电子速度场。新的EMHD重建技术已应用于磁层多尺度航天器在2017年7月11日遇到的磁尾重联的EDR，托伯特等人（2018年）对此进行了报道，https://doi.org/10.1126/science.aat2998，长谷川等人（2019年）用原始的无惯性版本进行了重建，https://doi.org/10.1029/2018ja026051，这表明新方法在恢复电场和电子流线上比原始版本表现更好。
