Stream-aligned Magnetohydrodynamics for Solar Wind Simulations
Stream-aligned Magnetohydrodynamics for Solar Wind Simulations
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DOI：
10.3847/1538-4357/ac400f
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发表时间：
2021-10
期刊：
影响因子：
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通讯作者：
I. Sokolov;Lulu Zhao;T. Gombosi
中科院分区：
文献类型：
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作者：
I. Sokolov;Lulu Zhao;T. Gombosi
我们提出了一个简化的磁流体动力学 (MHD) 数学模型，描述具有冻结磁场的高导等离子体的动力学行为，该模型受到存在参考系的假设的约束，其中磁场矢量 B 在每个点与等离子体速度矢量 u 对齐。我们将此解决方案称为“流对齐 MHD”(SA-MHD)。在该模型的框架内，感应方程中的电场 E = − u × B == 0 同样消失，能量方程中的电磁能通量（坡印廷通量）E × B == 0 也同样消失。同时，动量方程充分考虑了磁场对等离子体运动的力作用（安培力）。所提出模型的任何稳态解都是完整 MHD 方程组的合法解。然而，相反的说法是不正确的：在任意稳态磁场中，电场不必同样消失（但其旋度必须消失）。具体来说，可以在流对准 MHD (SA-MHD) 内有效地生成所谓的帕克螺旋形式的稳态（“环境”）太阳大气的真实三维解决方案，而不会损失通用性。
We present a reduced magnetohydrodynamic (MHD) mathematical model describing the dynamical behavior of highly conducting plasmas with frozen-in magnetic fields, constrained by the assumption that there exists a frame of reference, where the magnetic field vector, B , is aligned with the plasma velocity vector, u , at each point. We call this solution “stream-aligned MHD” (SA-MHD). Within the framework of this model, the electric field, E = − u × B ≡ 0, in the induction equation vanishes identically and so does the electromagnetic energy flux (Poynting flux), E × B ≡ 0, in the energy equation. At the same time, the force effect from the magnetic field on the plasma motion (the Ampère force) is fully taken into account in the momentum equation. Any steady-state solution of the proposed model is a legitimate solution of the full MHD system of equations. However, the converse statement is not true: in an arbitrary steady-state magnetic field, the electric field does not have to vanish identically (its curl has to, though). Specifically, realistic three-dimensional solutions for the steady-state (“ambient”) solar atmosphere in the form of so-called Parker spirals can be efficiently generated within the stream-aligned MHD (SA-MHD) with no loss in generality.