MHD Turbulent Power Anisotropy in the Inner Heliosphere
MHD Turbulent Power Anisotropy in the Inner Heliosphere
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DOI：
10.3847/1538-4357/ac70cb
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发表时间：
2022-07
期刊：
影响因子：
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通讯作者：
L. Adhikari;G. Zank;L.-L. Zhao-L.;D. Telloni
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作者：
L. Adhikari;G. Zank;L.-L. Zhao-L.;D. Telloni
从方差各向异性和相关各向异性的角度研究了帕克太阳探测器（PSP）和太阳轨道器（SolO）在第一轨道上观测到的慢太阳风中的各向异性磁流体动力学（MHD）湍流。我们使用Belcher & Davis方法（M1）和一种新的方法（M2），该方法将波动向量分解为平行和垂直的波动向量。M1和M2计算相对于平均磁场方向的横向和平行湍流分量。平行湍流分量被视为可压缩湍流，横向湍流分量被视为不可压缩湍流，其可以是Alfvénic或2D。横向湍流能量由M1和M2计算，横向相关长度由M2计算。我们分别从满足平均太阳风流速与平均磁场θ UB之间的夹角为（i）65° < θ UB < 115°或（ii）0° < θ UB < 25°（155° < θ UB < 180°）的横向湍流分量获得了二维和板层湍流能量以及相应的相关长度。我们发现，2D湍流分量是不典型的PSP观察近日点附近，但2D分量占主导地位的湍流内日球层。我们比较了一个几乎不可压缩的MHD湍流输运模型的详细的理论结果与PSP和SolO测量的观测结果，发现它们之间有很好的协议。
We study anisotropic magnetohydrodynamic (MHD) turbulence in the slow solar wind measured by Parker Solar Probe (PSP) and Solar Orbiter (SolO) during its first orbit from the perspective of variance anisotropy and correlation anisotropy. We use the Belcher & Davis approach (M1) and a new method (M2) that decomposes a fluctuating vector into parallel and perpendicular fluctuating vectors. M1 and M2 calculate the transverse and parallel turbulence components relative to the mean magnetic field direction. The parallel turbulence component is regarded as compressible turbulence, and the transverse turbulence component as incompressible turbulence, which can be either Alfvénic or 2D. The transverse turbulence energy is calculated from M1 and M2, and the transverse correlation length from M2. We obtain the 2D and slab turbulence energy and the corresponding correlation lengths from those transverse turbulence components that satisfy an angle between the mean solar wind flow speed and mean magnetic field θ UB of either (i) 65° < θ UB < 115° or (ii) 0° < θ UB < 25° (155° < θ UB < 180°), respectively. We find that the 2D turbulence component is not typically observed by PSP near perihelion, but the 2D component dominates turbulence in the inner heliosphere. We compare the detailed theoretical results of a nearly incompressible MHD turbulence transport model with the observed results of PSP and SolO measurements, finding good agreement between them.