短波─跳天波多普勒频移和展宽的变化

Variations of Doppler Shift and Spread for HF One-hop Skywave

本文通过对连续五年（１９８６—１９９０）短波一跳天波信号（收发相距为６７０Ｈｚ）的观测研究，给出了１０ＭＨｚ和１５ＨＨｚ信号回波的多普勒频移和展宽的年、月、日变化特性以及磁暴活动等对它们的影响，并从电离层电波传播角度探讨了这些参量变化的原因。

By analyzing five- year(1986 - 1990) HF one- hop skywave records of 10 and 15 MHz, the varianons of Doppler shift and spread are shown as that for the fixed observation circuit and frequency, the long term variation of Doppler shift is maximum in winter, and minimum in summer. its diurnal variation of Doppler shift is positive in the morning and negative in the afternoon, and become zero at noon.The Doppler spread of 10 MHz is always larger than that of 15MHz, and it tends to increase as the solar activity increases (from 0. 35 to 0. 65 zi ), while the spread of 15 MHz only increase slightly. The diurnal changes of Doppler spread decline to minimum (0.45Hz)at high noon, and increases in the morning and afternoon. The Doppler spread in the sunrise and sunset varies from 1,0 Hz to 0.7 Hz respectively. The average Doppler shift has no change with geomagnetic variation while Doppler spread apparently increases during the strong magnetic disturbances. Some explanations to the reasons of their variation are also given in the paper.