Fig. 5From: Ground-based VLF wave intensity variations investigated by the principal component analysisDependence of the PC3 coefficients on (a) Kp index, (b) AE index, and (c) standard deviation of the magnetic field magnitude measured by the Sodankylä magnetometer. Black points correspond to the values obtained for individual frequency–time spectrograms. Red lines show median values in given intervalsBack to article page