An Analytical Model of Turbulence in Parker Spiral Geometry and Associated Magnetic Field Line Lengths
An Analytical Model of Turbulence in Parker Spiral Geometry and Associated Magnetic Field Line Lengths
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DOI：
10.3847/1538-4357/aca892
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发表时间：
2022-12
期刊：
影响因子：
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通讯作者：
T. Laitinen;S. Dalla;C. Waterfall;A. Hutchinson
中科院分区：
文献类型：
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作者：
T. Laitinen;S. Dalla;C. Waterfall;A. Hutchinson
理解从太阳到行星际空间的磁连接对于将现场粒子观测与粒子的太阳源区联系起来至关重要。沿着大尺度帕克螺旋磁场的简单连接由于场线的湍流随机行走而变得复杂。在这篇文章中，我们提出了第一个日球层磁场的解析模型，其中湍流的主要2D分量横跨Parker螺旋。2D波场被补充了一个小波场分量，它在小日心距和大日心距处具有渐近的平板几何形状。结果表明，湍流使场线从太阳的一个小源区扩展到1 Au处60°的纵向和纬向范围，场线的角扩散的标准差为14°。小的源区映射到1 Au的经度和纬度的间歇性范围，这与太阳高能粒子强度的消失一致。场线的长度从标称的帕克螺旋长度1.17Au一直延伸到1.6Au，西翼及其后面的源场线比更靠近太阳圆盘中心的场线长得多。我们讨论了我们的发现对于理解带电粒子传播的意义，以及理解接近太阳的湍流特性的重要性。
Understanding the magnetic connections from the Sun to interplanetary space is crucial for linking in situ particle observations with the solar source regions of the particles. A simple connection along the large-scale Parker spiral magnetic field is made complex by the turbulent random walk of field lines. In this paper, we present the first analytical model of heliospheric magnetic fields where the dominant 2D component of the turbulence is transverse to the Parker spiral. The 2D wave field is supplemented with a minor wave field component that has asymptotic slab geometry at small and large heliocentric distances. We show that turbulence spreads field lines from a small source region at the Sun to a 60° heliolongitudinal and heliolatitudinal range at 1 au, with a standard deviation of the angular spread of the field lines of 14°. Small source regions map to an intermittent range of longitudes and latitudes at 1 au, consistent with dropouts in solar energetic particle intensities. The lengths of the field lines are significantly extended from the nominal Parker spiral length of 1.17 au up to 1.6 au, with field lines from sources at and behind the west limb considerably longer than those closer to the solar disk center. We discuss the implications of our findings for understanding charged particle propagation and the importance of understanding the turbulence properties close to the Sun.