利用Cluster资料对经验及抛物面磁场模式性能的研究

Cluster的观测区包括太阳风与磁层相互作用的关键区域.本文将Tsyganenko经验模式T96,T01及Alexeev抛物面模式A2000的模拟结果与Cluster的磁场资料进行了详细对比,研究了两种模式对于近地点分别位于日侧及夜侧磁层的不同Cluster轨道上磁场的模拟性能.结果表明: (1)Cluster近地点附近轨道上的磁场主要受Birkland电流影响,T96,T01能很好地估计电流系位置,但对其强度模拟有所偏差,由于A2000不包含Ⅱ区场向电流,因此模拟不出近地点附近的磁场扰动; (2)对于0＞Dst＞-100 nT情况,T96与T01性能相当,但由于缺少部分环电流,T96对于日侧昏线附近的磁场模拟偏差大; (3)T96与T01对夜侧近地点轨道上磁场模拟的均方根相对误差为40%左右,受极尖区电流影响,日侧时误差上升到50%,而A2000均方根相对误差明显偏大,均为58%左右.

Accuracy of Empirical and Paraboloid Magnetic Field Models Estimated by Cluster Magnetic Data

Since the Cluster passes through the crucial regions where the solar wind and the magnetosphere interact, this paper compares the empirical magnetic field T96, T01 models and the paraboloid A2000 model with Cluster magnetic data. The reliability of the three models for different orbit whose perigee is either on the dayside or on the nightside of the magnetosphere is examined. The results show that, (1) Magnetic filed near the perigees of Cluster orbits is mainly influenced by Birkland currents, the T01 and T96 models give a good estimation of the location of passage through the large-scale currents, while the modeled magnitude being not accurate, and due to the absence of II region field-aligned current, the A2000 model can't correctly predict the disturbance of magnetic filed near the perigee; (2) For cases of 0>Dst>-100 nT, the reliability of T96 is comparable to that of T01, while due to the absence of the partial ring current, the T96 model can't correctly reproduce the magnetic field near the dayside perigee close to the dusk region; (3) The residual RMS deviation of the T96 and T01 models is about 40 % of the average magnitude of the observed external field for nightside perigee cases, while due to the effect of currents near cusp, that increases to 50 % for dayside perigee cases. Contrastively, the residual RMS deviation of the A2000 model is apparently larger, which is 58 % of the observed field.