曲靖非相干散射雷达电离层E-F谷区电子密度日间变化特征初步分析

Preliminary analysis of daytime electron density in the ionospheric E-F valley based on the Qujing incoherent scatter radar observations

电离层E-F谷区是电离层探测和研究的薄弱环节之一.文中利用曲靖非相干散射雷达日间120~200 km的电子密度观测数据,初步分析了曲靖地区电离层E-F谷区的变化特征.发现E-F谷区结构依赖于地方时与季节,相对于正午存在对称性,同时表现为两种形态:一种在120~160 km存在明显谷区结构,谷底位于134~144 km;另一种的谷区很宽,谷底位于约130 m,在120~150 km电子密度随高度缓慢变化,160 km以上电子密度快速单调增加.一次耀斑爆发后129 km以下电子密度迅速增加,D层电子密度突然增强,而134 km以上变化不明显,可能与X射线增强有关.一次磁暴期间139~158 km电子密度变化不明显,177~196 km的电子密度出现了增强现象,可能与氧原子含量增加有关.

The ionospheric E-F valley is difficult to be measured due to its low ionisation. This paper presents the preliminary analysis of daytime electron density profiles in the E-F valley between 120 and 200 km measured by the Qujing incoherent scatter radar. These electron density profiles in the E-F valley depend greatly on the local time and season. There are two kinds of typical E-F valley profiles, of which one has the obvious valley structure in 120-160 km with the altitude of the minimal electron density 134-144 km and the other has a wider valley with a smooth profile between 120 and 150 km and monotonically increasing above 160 km, the valley is located at about 130 km. The electron density in 120-130 km shows the obvious enhancement after the solar flare burst below the altitude of 129 km and sudden enhancement in the D region, and no obvious variations above 134 km,which may be related to the solar Xray fulx enhancement. The electron density in 139-158 km shows no obvious variations and some enhancements in177-196 km in the geomagnetic storm event, which may be related to the oxygeon content enhancement.