Spectral power of low-latitude Pi 2 pulsations at the 210° magnetic meridian stations and plasmaspheric cavity resonances
Spectral power of low-latitude Pi 2 pulsations at the 210° magnetic meridian stations and plasmaspheric cavity resonances
复制标题
210°磁子午线站低纬度 Pi 2 脉动的频谱功率和等离子体层腔共振
DOI：
10.1186/bf03351670
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发表时间：
2000
期刊：
影响因子：
--
通讯作者：
K. Yumoto
中科院分区：
文献类型：
--
作者：
Ching;J. Chao;K. Yumoto
利用1991年210°磁子午线（MM）台站的磁场资料，研究了低纬π 2脉动。由于在大多数纬度上具有高度的相干性，参考仑平（189.5° MM，L = 1.06）地磁图上的相同波形，在210° MM台站识别出68个低纬Pi 2事件。经谱功率分析，低纬Pi 2脉动的前4个谐波频率之比约为1：（1.7 ± 0.1）：（2.3 ± 0.1）：（2.9 ± 0.1）。利用磁层内的abox模型，研究了非均匀环境磁场下的冷线性化磁流体波动方程和实际的Alfven速度剖面。选取适当的参数描述上述时间段的磁层环境，采用四阶龙格-库塔法进行数值计算。计算结果表明，等离子体层谐振腔的前四个谐波频率之比约为1：1.7：2.4：3.1，与实验结果一致。这表明210° MM低纬Pi 2脉动可能是磁尾脉冲源所产生的快压缩波驱动的等离子体层腔共振。
Pi 2 pulsations at low latitudes are examined with magnetic fields data at the 210° magnetic meridian (MM) stations in 1991. Due to high degree of coherence over most latitudes, 68 low-latitude Pi 2 events at the 210° MM stations are identified with reference to same waveforms on the magnetogram at Lunping (189.5° MM, L = 1.06). With spectral power analysis, the ratio of the first four harmonic frequencies of low-latitude Pi 2 pulsations is about 1: (1.7 ± 0.1): (2.3 ± 0.1): (2.9 ± 0.1). By using abox model for the inner magnetosphere, the cold linearized MHD wave equations are studied with realistic Alfven speed profile for nonuniform ambient magnetic fields. With appropriate parameters to depict the magnetospheric environments during the aforementioned period, numerical results are acquired with the fourth order Runge-Kutta method. It is found that the ratio of the first four harmonic frequencies of plasmaspheric cavity resonances is about 1: 1.7: 2.4: 3.1 that is consistent with data analysis. This suggests that low-latitude Pi 2 pulsations at the 210° MM stations may be plasmaspheric cavity resonances driven by fast compressional waves owing to the impulsive source at the magnetotail.