Effect of enhanced X-ray flux on the D and F layer ionospheric ionization during extreme solar events

When the Sun starts flaring, the Earth´s atmosphere receives increased amounts of X-ray and EUV fluxes. Consequently ionospheric ionization/absorption gets increased in a cause-effect relation during solar flares and CMEs. Moreover the extent of impact is different in different regions of the ionosphere. To establish the magnitude of correlation and extent of impact in different layers, data of X-ray intensity from geostationary satellite GOES and ionospheric parameter data (D & F layer) from Ionosonde over Okinawa (Japan) station (lat.26.3°N, long.158.7°E) were examined for ten X-class flares that occurred during the maximum phase of solar cycle 23 from 2000 to 2004. The data analysis revealed a positive and good correlation between fmin and X-ray intensity for D layer and NmF2 for F layer. However the correlation coefficient between fmin and X-ray intensity was found to be greater than between NmF2 and X-ray intensity. Which suggest that X-rays play a dominant role in D layer ionization than that in F layer.