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

  • H. Allawi , Moataz Jasim , Kareem Abdulameer Difar


-This study indicates the change in the amplitude of the very low frequency VLF signals throwing
back 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 - Iraq
The increase in amplitude occurred during a series of solar flares of class M8.1 and M3.7 during the days of
September 8 and 9, 2017 at various solar zenith angles. The usual daily change (without solar flare) shows a clear
contrast between the signal amplitude during the night and day and during sunrise and sunset. The increase in
amplitude was observed during the turbulent day, and it was found that it differs in its intensity, the period of its
occurrence and its amplitude according to the category of flare and the time of its occurrence, which is more
evident during the daytime period starting from sunrise and in the evening ending with sunset, when the D-layer
is ionized. We used the Geostationary Operational Environmental Satellites GOES data to find out the solar flame
class and when it occurred