Effects of Geomagnetic Storms on the Mid-Latitude D Region Ionosphere

The response of D Layer Preparation Time (DLPT) depth to geomagnetic storms during 2008-2011 is studied to investigate the effect of geomagnetic storms on the D layer of the ionosphere.The Very Low Frequency (VLF) signal at 19.6 kHz transmitted from the GBZ transmitter station Anthorn, UK (54N, 3W) and recorded by the AWESOME receiver at the Shamakhy Astrophysical Observatory named after N.Tusi, Shamakhy, Azerbaijan (40N, 48E) was used for analysis.Five geomagnetically disturbed days (Ap>26) were studied.A decrease in DLPT depth was observed for the storm day on October 11, 2008, while an increase was observed for all other storms.