Resonant harmonic Alfvén waves in the magnetosphere: A case study
Resonant harmonic Alfvén waves in the magnetosphere: A case study
复制标题
磁层中的谐振谐波：案例研究
DOI：
10.1029/ja089ia12p10757
复制
发表时间：
1984
影响因子：
--
通讯作者：
Wolfgang Baumjohann
中科院分区：
文献类型：
--
作者：
H. Junginger;Wolfgang Baumjohann
1979年4月11日，在地球静止卫星GEOS 2上测量到了强烈的日侧长周期电场和磁场波动。全天获得的电场和磁场频谱清楚地呈现出离散频带，同时持续了大约5个小时。典型周期为 260 s 的低频脉动仅出现在电场数据中（典型幅度为 0.3 mV/m），而高频振荡在横向磁场谱中占主导地位（典型周期为 95 s，典型幅度为 1 nT）。两个脉动的周期都向黄昏区域增加。观测到的脉动周期与测量的赤道电子密度、两个频段的电场和磁场幅度之比以及周期比的恒定性相结合，提供了强有力的证据，表明这两个频段代表基频和二次谐波模式本征振荡地磁场线。从测量中得出的较短周期和较长周期之间的平均比率（约 0.35）与理论上获得的比率略有不同，从而表明了当前可用模型的缺点。高频脉动的电场和磁场波动之间的相位关系、波印廷矢量的方向以及春分之后事件的发生表明，波浪能量的主要部分被馈送到南半球的振荡中，而不是靠近赤道面。
Strong dayside long-period electric and magnetic field fluctuations were measured on board the geostationary satellite GEOS 2 on April 11, 1979. The electric and magnetic field spectra obtained throughout this day clearly exhibit discrete frequency bands, lasting simultaneously for about 5 hours. The lower-frequency pulsation with a typical period of 260 s is only present in the electric field data (with typical amplitudes of 0.3 mV/m), whereas the higher-frequency oscillation dominates the transverse magnetic field spectra (typical period 95 s, typical amplitude 1 nT). The periods of both pulsations increase toward the dusk sector. The observed periods of the pulsations in conjunction with the measured equatorial electron densities, the ratio of the electric and magnetic field amplitudes for both frequency bands, and the constancy of the period ratio yield strong evidence that the two frequency bands represent fundamental and second harmonic mode eigenoscillations geomagnetic field lines. The mean ratio between the shorter and longer periods derived from the measurements (about 0.35) is slightly different from theoretically obtained ratios, thus indicating shortcomings of currently available models. The phase relationship between the electric and magnetic field fluctuations of the higher-frequency pulsation, the direction of the wave Poynting vector, and the occurrence of the event after the spring equinox indicate that the major part of the wave energy is fed into the oscillation in the southern hemisphere and not close to the equatorial plane.