Cluster observations of magnetic field disturbances caused by FACs in the mid-altitude cusps

作     者：Q.-H. Zhang,R.-Y Liu J.-Y Huang,Y-H. Liu, Z.-H. Xu (Polar Research Institute of China, Shanghai, China 200136) (School of Science, Xidian University, Xi''an 710071) 

会议名称：《第十一届全国日地空间物理学术讨论会》

会议日期：2005年

学科分类：070802[理学-空间物理学] 07[理学] 0708[理学-地球物理学] 

关 键 词：cusp IMF FACs boundary structure Cluster. 

摘      要：正Data from the four Cluster spacecraft during the mid-altitude cusp crossings on 10 September 2002 are presented. The encounters occur under conditions of weak and steady southward Interplanetary Magnetic Field （IMF）. The data show that there are the field-aligned currents （FACs） in the cusp causing large magnetic field disturbances. The boundary structures of the cusps are characterized by the FACs interfaces. A method for calculating the velocities of the interface based on multi-point measurements of spacecraft are introduced. Results show that the interfaces are roughly parallel to magnetic field lines, and their velocities are almost dawnward. The velocities have small values with respect to satellite’s velocity in the cusp crossings.