Studies On Autoscaling And Analysis Of Ionograms

The scaling and inversion of the ionospheric ionograms play important roles in ionospheric measurement and research, which has been a topic full of continuous scientific and practical interest for ionospheric scientists and researchers for a long time. Combining other methods of ionogram scaling and inversion, a new method based on the empirical orthogonal function (EOF) analysis of ionospheric electron density profiles is developed and described in this paper. And the applications of this method for ionogram F2 layer scaling and analysis in CADI, Digisonde and film ionograms are also discussed.Most of other methods currently used usually include two separate steps. They firstly emphasize the accurate scaling of ionogram traces by combining the image recognition and the analytical function fitting techniques. And then make inversion of the electron density profile using some ionospheric models and thus obtain the ionospheric parameters. In this paper, a method based on the empirical orthogonal function (EOF) analysis of ionospheric electron density profiles is proposed for the automatic scaling and analysis of ionospheric parameters. The EOFs are derived from the electron density profiles, which are inversed from the measured ionograms or directly calculated from IRI model. And the electron density profiles corresponding to the measured ionograms are represented using a linear series of EOFs. The calculated traces from the series are used to match the measured ionogram traces approximately. Thus the scaling of ionogram trace and inversion of electron density profile are completed simultaneously.The characteristics of this new method are obtained by appling it to ionogram analysis of CADI and Digisonde, which are two widely used ionosonde nowadays. The results of CADI ionograms show that: In quite conditions, the acceptability of foF2 (the critical frequency), hmF2 (the peak height) and MUF(3000)F2 (Maximum Usable Frequency) of F2 layer are 83.8%, 85.5% and 74.5% respectively. During magnetic storm periods, the acceptability of foF2, hmF2 and MUF(3000)F2 are 82.4%, 84.5% and 74.3%. The acceptability of foEs (critical frequency of Es) is as high as 93.1%. The analysis results of Digisonde ionograms show that the acceptability of foF2, hmF2 and MUF(3000)F2 are 83.5%,91.1% and 79.2% respectively. These above results show that our method is comparable to or even a little better than the widly used method ARTIST4.0 as to the analysis of F2 parameters. So our method owns good acceptability. And the performance of our method in different conditions shows weak variations and has little relation to the complicate varations of the measured ionograms. So this method has good stability. Moreover, the method only needs an amplitude array as input and the polarization information isn't necessary so it is universal and can be applied to many kinds of ionograms, even the film ionograms.The parametering research of ionospheric physics model is an important content for modeling research of near-earth space environment. And the decomposition, modeling and forecasting of ionospheric electron density profiles are the key points of the modeling research of ionospheric physics. The EOF analysis owns the good performance of quick convergence and high accuracy. A few EOFs can represent most varations of ionospheric electron density profiles. Consequently, the results in this paper can show the feasibility and availability of using EOFs to analysize and model the electron density profiles.CADI (Canadian Advanced Digital Ionosonde) is a widely used ionosonde nowadays but its software of ionogram scaling and analysis is insufficient or imperfect. Recently, a CADI ionosonde was introduced and installed at Beijing (40.3°N, 116.2°E), China and will start routinely operation. To process the CADI ionograms conveniently, a Windows software is developed to real-time and offline process these ionograms and perform the real-time monitoring and analysis of ionospheric space weather. The results show that the method owns good reliability and accuracy. And can be applied to real-time scaling, analysis, monitoring and internet release of CADI ionogram parameters, which is important for the real-time monitoring and analysis of the ionospheric space weather.Furthermore, we apply this method to the film scanned ionograms and make some tests. The results show that the acceptability of foF2 is about 75%, which is basically applicable. Thus our method provides a new idea to automatically scale and process large number of the recorded film ionograms.