用电离层特性参量提取等效风场信息

DERIVING EQUIVALENT WINDS FROM IONOSPHERIC F-LAYER DATA

导出了利用中低纬电离层特性参量获取电离层F层峰区高度上等效风场（包含电场和风场信息在内）的基本方程,并尝试用该方法从电离层特性参量（峰高和临频）提取等效风场信息.利用武汉站 DGS-256电离层数字测高仪数据及由美国 Massachusetts Lowell大学最新版的剖面反演程序换算得到F层峰高,获得了武汉地区夏季至日点附近、冬季至日点附近、冬季地磁特别宁静的九天和冬季平均等效风场的初步特征.并利用 Fejer经验电场模式计算冬季电场引起的垂直漂移,估计电场和风场对武汉地区的垂直等效风场的贡献大小.结果表明:等效风场呈现出白天与夜晚幅度和方向的差异、至日点附近冬季与夏季白天的幅度差异以及明显的凌晨凹陷现象;平均情况下,垂直等效风场幅度和方向的变化主要是由中性风引起,受电场的影响不大.

Deriving winds or electric fields from ionospheric data is very important for understanding thermospheric dynamics and ionospheric electrodynamics when the direct measurements are very limited. The methods previously used need a non-wind reference height, which is difficult to be accurately determined. In this paper, we develop a method to deduce the equivalent winds including effects of both neutral winds and electric fields from measured ionospheric F-layer data. The method avoids the problem of a non-wind reference height.Ionospheric data are available from the DGS-256 Digisonde in Wuhan to provide the critical frequency of F layer and its peak height with the aid of the new version SAO-Explorer software by University for Massachusetts Lowell in American. Using this method, some preliminary characteristics of equivalent winds in the ionospheric F layer over Wuhan are deduced during the summer and winter solstices, nine days ofvery quiet magnetic conditions in Winter of the year 2000-2001. The mean pattern of the vertical equivalent winds during the winter is also calculated. Results show that there are clearly day-to-day variations of vertical equivalent winds over Wuhan. Obvious morning decent features are showed both in summer solstices and winter months. The difference from summer to winter solstice daytime vertical equivalent winds is discussed. In terms of the winter northward perpendicular drifts calculated from Fejer empirical electric fields, we find that the electric vertical drift generally contributes insignificantly to the vertical equivalent winds over Wuhan. Therefore, the mean equivalent winds are composed mainly from the meridional neutral winds.