Effect of Interplanetary Magnetic Field on the Field-aligned Currents Occurrence in the Magnetotail
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摘要: 利用Cluster卫星的磁场和等离子体探测数据, 研究了行星际磁场(IMF)时钟角(clock angle) Φ和锥角(cone angle) θ对磁尾等离子体片边界层(PSBL)区场向电流发生率的影响. 当时钟角Φ >0时, 磁尾场向电流 的发生率较高, 这表明磁尾场向电流的发生与昏向太阳风条件更为密切; 当 90°<|Φ|<180°时, 场向电流的发生率较高, 这表明 场向电流的发生与南向IMF更为密切. 当锥角θ <30°时(即IMF与 日地连线夹角较小时)场向电流的发生率较低. 而当θ> 30°时, 场向电流在90°<|Φ|<180°的情况下发生率明显增大, 这说明南向IMF情况下, 场向电流发生率明显增大. 但是当|Φ|<90°时 (北向IMF情况下), 尽管θ很大, 场向电流的发生率并未明显增大. 当θ>70°时, 且在140°< < i>Φ<160°的行星 际磁场条件下, 磁尾等离子体片边界层区场向电流的发生率最大.Abstract: Using the magnetic field and plasma data from Cluster spacecraft, the effect of Interplanetary Magnetic Field (IMF) clock angle Φ and cone angle θ on the Field-Aligned Currents (FAC) occurrence rate at the Plasma Sheet Boundary layer (PSBL) in the magnetotail is investigated. There were more FAC cases occurred when IMF was within the 0°< Φ< 180° clock angle range comparing with the range of -180°< Φ<0°. It indicated that FAC occurrences were associated with duskward IMF (IMF By>0). Also, there were more FAC cases occurred when the IMF was within the 90° < |Φ|< 180° clock angle range. It supported that FAC occurrences were associated with southward IMF (IMF Bz<0). Most of the FAC cases occurred when IMF was within the θ>30° cone angle. In addition, A few of FAC cases occurred when the IMF clock angle was in the θ<30° range regardless of the value of Φ. The occurrence rate of FAC was the largest when θ> 30° and 140°< Φ<160°.
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