New method for determining central axial orientation of flux rope embedded within current sheet using multipoint measurements

• Published in: Science China. Earth sciences Vol. 59; no. 10; pp. 2037 - 2052
• Main Authors: Li, ZhaoYu, Chen, Tao, Yan, GuangQing
• Format: Journal Article
• Language: English
• Published: Beijing Science China Press 01.10.2016; Springer Nature B.V
• Subjects: Cluster analysis; Earth and Environmental Science; Earth Sciences; Fluctuations; Geometry; Magnetic fields; Physical properties; Research Paper; Variance analysis; 几何模型; 多点测量; 电流片; 磁场结构; 磁通量; 轴向定位; 轴对称; 通量传输事件; Cluster data; Current sheet; Flux rope; Flux rope orientation; Magnetopause; Transfer events
• ISSN: 1674-7313; 1869-1897
• DOI: 10.1007/s11430-015-0252-6

A new method for determining the central axial orientation of a two-dimensional coherent magnetic flux rope （MFR） via multipoint analysis of the magnetic-field structure is developed. The method is devised under the following geometrical assumptions： （1） on its cross section, the structure is left-right symmetric; （2） the projected structure velocity is vertical to the line of symmetry. The two conditions can be naturally satisfied for cylindrical MFRs and are expected to be satisfied for MFRs that are flattened within current sheets. The model test demonstrates that, for determining the axial orientation of such structures, the new method is more efficient and reliable than traditional techniques such as minimum-variance analysis of the magnetic field, Grad-Shafranov （GS） reconstruction, and the more recent method based on the cylindrically symmetric assumption. A total of five flux transfer events observed by Cluster are studied using the proposed approach, and the application results indicate that the observed structures, regardless of their actual physical properties, fit the assumed geometrical model well. For these events, the inferred axial orientations are all in excellent agreement with those obtained using the multi-GS reconstruction technique.