An Observation of typical daily variations of the VLF amplitude signal by investigating sunrise/sunset received at An-Nasiriyah station

-This study indicates the change in the amplitude of the very low frequency VLF signals throwingback by the ionosphere D-layer, during the sensitized solar flare using the navigational transmitter signal DHO(23.4 KHz) and GQD (22.1 KHz) which were detected at the Sudden Ionospheric Disturbance SIDs receiving.station in Nasiriyah - IraqThe increase in amplitude occurred during a series of solar flares of class M8.1 and M3.7 during the days ofSeptember 8 and 9, 2017 at various solar zenith angles. The usual daily change (without solar flare) shows a clearcontrast between the signal amplitude during the night and day and during sunrise and sunset. The increase inamplitude was observed during the turbulent day, and it was found that it differs in its intensity, the period of itsoccurrence and its amplitude according to the category of flare and the time of its occurrence, which is moreevident during the daytime period starting from sunrise and in the evening ending with sunset, when the D-layeris ionized. We used the Geostationary Operational Environmental Satellites GOES data to find out the solar flameclass and when it occurred