Multiple Flux Rope Events at the High-Latitude Magnetopause on January 26, 2001: Current Density Calculation
Glassmeier, K. -H.; Shen, Chao; Cao, Jin-Bin; Huang, Zong-Ying; Pu, Zu-Yin; Xiao, Chi-Jie; Fu, Sui-Yan; Xie, Lun; Liu, Zhen-Xing; Shi, Jian-Kui; Lu, Li; Wang, Nai-Quan; Chen, Tao; Fritz, T.; Zhong, Qui-Gang
China, United States, Germany
Abstract
A systematic comparison is carried out for three methods of current density calculation based on simultaneous magnetic field measurements of four-spacecraft Cluster mission. It is demonstrated analytically and numerically that within the linear approximation, all these methods lead to exactly the same results. As a case study, the current density of multiple flux rope events at the high-latitude magnetopause on January 26, 2001 is investigated. The result shows that an intense current flows inside the ropes with the current density reaching as high as about 10-8A/m2. The current inside rope is valuable with small relative errors. It is also found that the current direction is almost parallel to the axis of flux rope obtained through the magnetic minimum variance analysis (BMVA). Finally, it is proposed that the current MVA method (CMVA) has great effectness for study of flux rope geometry, particularly when the BMVA is insufficient to determine the flux rope orientation.