This paper describes an investigation of the three dimensional (3-D) magnetic fields produced by currents flowing in plasmas that are confined in stellarators and in tokamaks with magnetic field ripples. A simple semianalytical procedure is proposed and a linear 3-D equation is derived that makes it possible to investigate the influence of finite pressure effects and plasma currents on the ripples of the longitudinal magnetic field. Analytical estimations are presented that can be useful for the analysis of the transport properties of finite beta plasmas. It is shown that the accuracy of the experimental identification of the magnetohydrodynamic (MHD) equilibria can be improved using external measurements of the 3-D magnetic fields. This method appears to have considerable promise for the investigation of fairly weak effects, as for example, for distinguishing bootstrap current profiles in stellarators. Analytical expressions for the 3-D external magnetic fields produced by plasma currents are derived that can be used for a rough interpretation of the experimental data
本文描述了对在仿星器以及具有磁场波纹的托卡马克中约束的等离子体电流所产生的三维（3-D）磁场的研究。提出了一种简单的半解析方法，并推导出一个线性三维方程，使得能够研究有限压力效应和等离子体电流对纵向磁场波纹的影响。给出了可用于分析有限β等离子体输运特性的解析估计。结果表明，利用外部三维磁场测量可以提高磁流体动力学（MHD）平衡实验识别的精度。该方法似乎对研究相当微弱的效应具有相当大的前景，例如区分仿星器中的自举电流分布。推导出了由等离子体电流产生的外部三维磁场的解析表达式，可用于对实验数据进行粗略解释。