Detection of periodic disturbances in LOFAR calibration solutions

Calibration solutions of astronomical observations contain information on ionospheric disturbances with a sensitivity of less than 1 mTECU. We apply a complex Morlet wavelet transform to one of the least disturbed datasets to detect the wave parameters of periodic disturbances and check the sensitivity levels to geomagnetic conditions characterised with the auroral electrojet index. We obtain two dominant frequencies of 6 minutes and 14 minutes. We also note that AE index variations time occurence coincides with peaks in the LOFAR scaleogram. Such high sensitivity to geomagnetic conditions may prove beneficial for future study of the ionosphere-plasmasphere interaction.