1986年2月强磁暴对中低纬VHF电波闪烁影响的初步分析

本文研究了1986年2月强磁暴对我国中低纬地区电波闪烁活动的影响。着重分析了在武昌接收到的136MHz卫星信号的反常闪烁现象,计算了武昌暴时闪烁的极大熵功率谱密度。发现8日闪烁的幂律谱大都在约500m尺度附近呈现出明显的“膝（knee）”;谱指数比平时大,以膝为界,较大尺度上的谱指数值在2.6至3.6之间,平均为3.1,较小尺度上的谱指数平均为5.1,最大可达5.9;且在同一谱图上,有时出现不止一个“膝”,出现双膝时,最大谱指数可达8.9日的闪烁谱与8日有较大差异,但与非暴时的多数谱类似,大多未出现明显的“膝”,且谱指数较小,平均为2.8。本文还对引起闪烁的电离层不规则结构的起源机制作了初步讨论,以解释上述现象。

EFFECTS OF THE FEBRUARY 1986 MAGNETIC STORM ON IONOSPHERIC SCINTILLATIONS AT LOW-MIDDLE LATITUDES

The effects of the severe geomagnetic storm in Feb. 1986 on ionospheric scintillations of VHF satellite signals at low-middle latitudes have been investigated, giving emphasis of the unusual scintillation activities and the characteristics of storm-time scintillation spectra computed by maximum entropy method at Wuchang. It is found that almost all of the scintillation spectra on Feb. 8 exibit a distinct knee at a spact scale about 500 m and have multiple spectral indices larger than usual, such as from 2.6 to 3.6 with an average 3.1 at the scale lengths longer than that at which the knee lies and from 3.6 to 5.9 with an average 5.1 at the shorter scale lengths. Moreover, more than one knee appear sometimes in a spectrum on Feb. 8, and the largest magnitude of spectral index reaches 8.0. In contrast, the spectra for Feb. 9 exibit almost no distinct knee and show smaller spectral index with an average 2.8. In order to explain some phenomena above, a preliminary discussion on the generation mechanism of the ionospheric irregularities causing the storm-time scintillations has been made.