Effect of the Abnormal Propagation Conditions on the LF Signals

It is shown from the analyses of the observed data of LF skywaves and the experimental results that the reason why the amplitude and phase of the LF skywaves become suddenly abnormal is related to the solar-geophysical phenomenon.Therefore,the effect of the abnormal propagation conditions on the LF skywaves should be taken into account in the highly accurate results of the time service.