The magnetopause for large magnetic shear: AMPTE/IRM observations
The magnetopause for large magnetic shear: AMPTE/IRM observations
复制标题
DOI：
10.1029/ja091ia10p11099
复制
发表时间：
1986-10
影响因子：
--
通讯作者：
G. Paschmann;I. Papamastorakis;Wolfgang Baumjohann;N. Sckopke;C. Carlson;B. Sonnerup;H. Lühr
中科院分区：
文献类型：
--
作者：
G. Paschmann;I. Papamastorakis;Wolfgang Baumjohann;N. Sckopke;C. Carlson;B. Sonnerup;H. Lühr
观测了21次AMPTE/AMTE通过昼侧（当地时间0800-1600时）低纬磁层边界区的过程，所有这些过程都表现为磁层顶的大磁切变。这项研究的目的是利用改进的准确度和时间分辨率的等离子体测量，重新检查高速流动的发生，作为磁层顶重联过程的标志。在21次飞行中，共有12次显示出高速气流穿过磁层顶。这些流动的持续时间有时短至10 s，很少超过30 s。高速流动的发生与β（等离子体与磁压力的比值）呈负相关。对于β 2，平均比率较低（ΔV* = 0.18）。我们尝试性地解释这一点，以表明重联可能优先发生在低β值。对9个高速流场进行了定量动量和能量平衡试验。观测结果和理论预测之间的一致性通常相当好。从动量平衡推导出的正常磁场Bn的符号与从测量的质子热通量方向独立推断出的磁连接的意义一致。在一种情况下，观测结果表明，卫星可能已经穿越了重联过程的扩散区。动量平衡的结果表明，有时在磁层顶和边界层中的离子的有效质量是质子质量的两倍。
A total of 21 passes of AMPTE/IRM through the dayside (0800–1600 hours local time) low-latitude magnetospheric boundary region have been examined, all of which were characterized by large magnetic shear across the magnetopause. The purpose of the study was to use the improved accuracy and time resolution of the IRM plasma measurements to reexamine the occurrence of high-speed flows as signatures of the reconnection process at the magnetopause. A total of 12 of the 21 passes showed magnetopause crossings with high-speed flows. The duration of these flows was sometimes as short as 10 s and rarely more than 30 s. The occurrence of high-speed flows is inversely correlated with β, the ratio of plasma to magnetic pressure. For β 2 the average ratio is low (ΔV* = 0.18). We tentatively interpret this to indicate that reconnection may occur preferentially for low β values. A total of nine high-speed flows were subjected to quantitative momentum and energy balance test. The agreement between observations and theoretical predictions was generally quite good. The signs of the normal magnetic field, Bn, deduced from the momentum balance agreed with the sense of magnetic connection inferred independently from the measured proton heat flux direction. In one case the observations suggest that the satellite may have traversed the diffusion region of the reconnection process. The momentum balance results indicate that at times the effective mass of the ions in the magnetopause and boundary layer was of the order of twice the proton mass.