Multi-frequency Doppler Fast Detection and Analysis of Meso-micro Scale Ionospheric Disturbances

Measuring the HF Doppler frequency shifts of ionospheric echoes is one of the important ways to study ionospheric disturbances. We use the real-time detection method based on measuring the phase-change rate of single frequency signals, and obtain continuous high-precision multi-frequency Doppler ionograms to achieve fast detection and study of meso-micro scale ionospheric disturbances. This method is applied to the multi-frequency detection system which is jointly developed by the Chinese Academy of Sciences and South-Central University for Nationalities. It is verified that the Doppler resolution obtained from this platform can be up to 0.039Hz and the minimum ionogram period is less than 1 minute. We collect a long-time raw data of the ionosphere based on this new detection method and platform in Wuhan observatory. Through the way of acquiring high-precision Doppler frequency shifts and the method of inversing the normal velocity of electron concentration isosurface, the Doppler ionograms and vertical disturbed velocity of O waves are obtained. Furthermore, the real-time changes of ionospheric disturbances with time and space are deduced. By the spectrum analysis on these time domain signals, preliminary results show that these disturbances are mainly mesoscale TIDs motivated by the Polar activities which often appear in winter in central China. This paper also compares the three commonly used inversion methods. The results show that the ionospheric disturbances have almost the same change trends. It indicates that the observation data and the research methods are reliable and stable, which provides an important basis for observing and researching the multi-frequency and multi-point propagation characteristics of ionospheric disturbances.