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

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 X-ray fulx enhancement. The electron density in 139−158 km shows no obvious variations and some enhancements in 177−196 km in the geomagnetic storm event, which may be related to the oxygeon content enhancement.