开关间歇性是地磁脉冲产生的一种可能机制
On-off Intermittence as a Possible Mechanism of Geomagnetic Impulse Generation
摘要：
本文利用南、北半球几个高纬台站的多年观测资料，研究了磁脉冲事件（MIEs）振幅的空间分布。结果表明，脉冲幅度统计分布函数的尾部可用f（A）= A**（-b）形式的幂函数逼近，其中A为脉冲幅度，b为幂指数，其取值范围为1 ~ 5。实验证实了先前提出的假设，即脉冲产生制度定性地对应于开-关不稳定性的模型。我们认为开关不稳定性模型是MIE产生的可能机制之一。它被发现，大多数分析的统计分布的MIEs振幅的指数b超过2，这一事实是典型的混沌制度称为强湍流。在某些情况下，指数b接近于1，这一事实对于弱湍流介质中产生的区域是典型的。结果表明：（1）磁层高纬度地区的等离子体湍流度高于低纬度地区，（2）磁层午后区的等离子体湍流度高于午前区，（3）北半球和南半球的等离子体湍流度分别在夏季和冬季较强;（4）在太阳活动的增长阶段，磁层等离子体的湍流比下降阶段强。功率指数b对太阳风参数和IMF的依赖性表明行星际条件对MIE形成的高纬磁层等离子体的影响。
英文摘要：
Using the many-year observations at several high-latitude observatories in the Northern and Southern Hemispheres, the regularities in distribution of magnetic impulse events (MIEs) amplitudes are studied. It is shown that the tails of the functions of statistical distributions of impulse amplitudes are approximated by a power function of the form f (A) = A**(-b), where A is the impulse amplitude, and b is the power index laying in the range from 1 to 5. Experimental confirmation is obtained to the hypothesis suggested earlier that the impulse generation regime qualitatively corresponds to the model of on-off intermittency. It is assumed that the model of the on-off intermittency may be considered as one of the possible mechanisms of MIEs generation. It is found that the majority of the analyzed statistical distributions of MIEs amplitudes have the index b exceeding 2, the fact being typical for chaotic regimes called the strong turbulence. In some cases the index b is close to the unity, this fact being typical for the regimes generated in weakly turbulized medium. The results obtained make it possible to assume that: a) at higher magnetospheric latitudes, the plasma turbulence degree is higher that at lower latitudes, b) in the afternoon sector of the magnetosphere, the plasma is stronger turbulized than in the prenoon sector; c) in the Northern and Southern Hemispheres the magnetospheric plasma is stronger turbulized in summer and winter, respectively; d) at the growth phase of solar activity the magnetospheric plasma is stronger turbulized than at the declining phase. The dependence of the power index b on the solar wind parameters and IMF demonstrates the influence of interplanetary conditions on the high-latitude magnetosphere plasma where MIEs are formed.
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