Application of the hf doppler observations to the study of spread-f

This paper demonstrates the application of the HF Doppler shift observations to the study on ionospheric Spread-F with observational cases. These cases show that the HF Doppler shift observation is continuous so that the evolution process of the ionospheric spread-F can be clearly understood in the view of observations. The HF Doppler frequency shifts are all sensitive to the scattering of the echoes caused by ionospheric irregularities, to the various scale of traveling ionospheric disturbances (TIDs), and to sudden frequency deviation (SFD) caused by solar flare. It has good advantage to investigate the physical mechanism of spread-F and the correlation between the spread-F and the ionospheric background disturbances according to the time series of the ionospheric disturbances in observational records. The HF Doppler shift can observe the different time scales of the spread-F (from less than 1 hour to more than several hours) completely. It can avoid from losing in the time series in records of the spread-F occurrence and can decide the precise start and end time of the spread-F. Beside the obvious advantage, the HF Doppler also has some limitations in observations, such as the spatial resolution. With comprehensive observations and data analysis, HF Doppler observations can provide evidence for studying the physical mechanisms of the spread-F and forecasting the ionospheric disturbances.