Magnetic Helicity Estimations in Models and Observations of the Solar Magnetic Field. Part I: Finite Volume Methods
Magnetic Helicity Estimations in Models and Observations of the Solar Magnetic Field. Part I: Finite Volume Methods
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太阳磁场模型和观测中的磁螺旋度估计。
DOI：
10.1007/s11214-016-0299-3
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发表时间：
2016-10
影响因子：
10.3
通讯作者：
Yang Shangbin
中科院分区：
文献类型：
--
作者：
Valori Gherardo;Pariat Etienne;Anfinogentov Sergey;Chen Feng;Georgoulis Manolis K.;Guo Yang;Liu Yang;Moraitis Kostas;Thalmann Julia K.;Yang Shangbin
磁螺旋度是理想磁流体力学的守恒量，具有逆湍流级联的特征。因此，它经常被称为驱动各种天体物理和实验室等离子体磁场产生和结构的基本物理量之一。我们在这里首次系统地比较了现有的六种估计有限体积内已知磁场螺旋度的方法。所有这些方法都经过审查、基准测试和相互比较，并专门测试其准确性和对错误的敏感性。为此，我们考虑了四组数值试验，范围从三维，无力平衡的解决方案，到磁流体动力学数值模拟。几乎所有的方法都被发现在所有的测试中产生相同的螺旋度值在几个百分点之内。在本文采用的与太阳更相关和更现实的试验中，即对喷发通量绳的模拟，除一种方法外，所有方法得到的计算值的误差仅为3%，这表明这些方法在适当的参数范围内的可靠性和相互一致性。然而，不同的方法对数值分辨率和输入场螺线管特性误差的敏感性存在差异。除了有限体积方法外，我们还简要讨论了一种从磁场线的扭转估计螺旋度的方法，以及一种利用磁场在一个边界的值和日冕最小连通性而不是预先定义的三维磁场解的方法。
Magnetic helicity is a conserved quantity of ideal magneto-hydrodynamics characterized by an inverse turbulent cascade. Accordingly, it is often invoked as one of the basic physical quantities driving the generation and structuring of magnetic fields in a variety of astrophysical and laboratory plasmas. We provide here the first systematic comparison of six existing methods for the estimation of the helicity of magnetic fields known in a finite volume. All such methods are reviewed, benchmarked, and compared with each other, and specifically tested for accuracy and sensitivity to errors. To that purpose, we consider four groups of numerical tests, ranging from solutions of the three-dimensional, force-free equilibrium, to magneto-hydrodynamical numerical simulations. Almost all methods are found to produce the same value of magnetic helicity within few percent in all tests. In the more solar-relevant and realistic of the tests employed here, the simulation of an eruptive flux rope, the spread in the computed values obtained by all but one method is only 3 %, indicating the reliability and mutual consistency of such methods in appropriate parameter ranges. However, methods show differences in the sensitivity to numerical resolution and to errors in the solenoidal property of the input fields. In addition to finite volume methods, we also briefly discuss a method that estimates helicity from the field lines’ twist, and one that exploits the field’s value at one boundary and a coronal minimal connectivity instead of a pre-defined three-dimensional magnetic-field solution.
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影响因子：
4.6
作者：
W. Ames;C. Brezinski
通讯作者：
W. Ames;C. Brezinski
影响因子：
--
作者：
Xing-zhong Chen
通讯作者：
Xing-zhong Chen
影响因子：
6.5
作者：
C. Alissandrakis
通讯作者：
C. Alissandrakis
DOI：
10.1088/2041-8205/759/1/l4
发表时间：
2012-09
期刊：
The Astrophysical Journal Letters
影响因子：
--
作者：
K. Tziotziou;M. Georgoulis;N. Raouafi
通讯作者：
K. Tziotziou;M. Georgoulis;N. Raouafi
影响因子：
25.2
作者：
B. Lites
通讯作者：
B. Lites