地-电离层波导中甚低频波昼夜过渡期特性研究

Study on Day-to-Night Transition Characteristics of VLF Radio Wave in Earth-Ionospheric Waveguide

建立了地-电离层波导中甚低频电磁波在昼夜过渡期的传播模型,导出了计算昼夜过渡期接收点场强幅度与传播相位的理论公式,分析了季节的改变,白天和黑夜的长短等因素对其产生的影响。理论分析结果表明,接收点的相位昼夜变化近似于一个梯形,其中过渡期的变化即为两个斜边,对应的场强幅度变化出现相应的极大与极小值,而模转换干涉相位偏差即为叠加于斜边上的起伏。实验测试结果证实了理论公式的正确性。

The model of very low frequency（VLF） radio waves propagating in earth-ionospheric waveguide during the day-tonight transition period was built. Theoretical formulas to compute the field intensity and phase of the receive antenna were derived.The research identified the roles played by the various contributing factors such as season alternation,difference of diurnal hours and nocturnal hours,etc. Theoretical analyses show that the phase diurnal variations form a trapezoid approximatively,and the two hypotenuses represent the variations of the day-to-night transitional stage. The corresponding variations of the field amplitude represent the maximum and minimum values,and the fluctuations overlaid on the hypotenuses are the phase deviations of mode shift interference.The predicted results agree well with experimentally measured curves.