低纬哨声通过低电离层传播的透射特征——全波解

TRANSMISSION CHARACTERISTICS OF LOW LATITUDE WHISTLERS THROUGH THE LOWER IONOSPHERE——FULL WAVE SOLUTION

本文利用全波解方法研究了低纬哨声通过低电离层传播的过程。文中主要计算了哨声波的透射损失和反射系数随投射角与方位角的变化,并结合哨声多站同时观测结果进行了简要的讨论。全波解数值计算结果表明,透射损失随投射角的变化具有南北不对称性,当波矢沿磁力线方向时透射损失最小,且这种不对称性随磁倾角的减小而明显加剧。计算结果还表明,下行哨声的内反射系数基本上不随投射角而变化;但随波频率的升高而减小,并伴有数个相间的极大和极小值,这可能导致哨声回波频谱畸变。

In this paper the transmission property of low latitude whistlers through the lower ionosphere has been investigated by means of full wave technique.The emphasis is put on the dependence of the transmission loss and reflection coefficient on the incident and azimuth angles.Besides,some computation results are briefly discussed in comparison with simultaneous multi-stationed observations.It is found that the variation of whistler transmission loss with the incident angle exhibits an asymmetry in south-north direction,which becomes more severe with decreasing dip,and that the transmission loss reaches its minimum of - 7dB for one-hop whistlers when the wave normal is parallel to the geomagnetic force line.The computation results also show that the inner reflection coefficient of downgoing whistlers is independent of the incident angle,while it decreases with increasing wave frequency,accompanying with oscillation that may lead to distortion of the frequency spectra of whistlers and their echoes.