THE TOPOLOGICAL PROPERTIES OF MAGNETIC HELICITY
THE TOPOLOGICAL PROPERTIES OF MAGNETIC HELICITY
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DOI：
10.1017/s0022112084002019
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发表时间：
1984-01-01
影响因子：
3.7
通讯作者：
FIELD, GB
中科院分区：
文献类型：
--
作者：
BERGER, MA;FIELD, GB
讨论了磁螺旋度与磁力线拓扑结构的关系。如果空间被划分成一系列的通量管，磁螺旋度产生于通量管内的内部结构，如扭曲和扭结，以及通量管之间的外部关系，即链接和打结。旋数和扭数的概念是从生物学文献中引入的，用来描述磁通管绕轴的旋度和轴本身的结构对螺旋度的贡献。如果空间子体积不受磁表面的约束，则不存在绝对的螺旋度度量。然而，这里提出了一个拓扑意义和规范不变的相对措施的螺旋度等体积。计算了这一相对测度的时间导数，得到了拓扑结构跨边界流动的表达式。
The relation of magnetic helicity to the topological structure of field lines is discussed. If space is divided into a collection of flux tubes, magnetic helicity arises from internal structure within a flux tube, such as twist and kinking, and external relations between flux tubes, i.e. linking and knotting. The concepts of twist number and writhing number are introduced from the mathematical-biology literature to describe the contributions to helicity from twist about the axis of a flux tube, and from the structure of the axes themselves.There exists no absolute measure of the helicity within a subvolume of space if that subvolume is not bounded by a magnetic surface. However, a topologically meaningful and gauge-invariant relative measure of helicity for such volumes is presented here. The time derivative of this relative measure is calculated, which leads to an expression for the flow of topological structure across boundaries.