[1] A real-time mapping model of f o F 2 in northern China was established using neural networks (NNs). To avoid the local minimum problem associated with traditional NNs, a newly improved genetic algorithm-based NN (GA-NN) was developed using the input parameters of solar activities, geomagnetic activities, neutral winds, seasonal information, and geographical coordinates. The f o F 2 data were extracted by inversing the oblique ionograms obtained from the oblique ionosondes of the China Ground-based Seismo-ionospheric Monitoring Network every 30 min for the period from August 2009 to December 2011. The data associated with five transmitter stations (Beijing, Changchun, Qingdao, Xinxiang, and Suzhou) and one receiver station in Binzhou were considered the input parameters for the real-time f o F 2 mapping model, and the data from the Dalian and Jinyang transmitter stations were used to verify the results. The Jining transmitter station data were used to test the capability of the model. The root-mean-square error and percent deviation were calculated to estimate the performance of the model. The correlation coefficient was used to evaluate the correlation of observed and predicted values. In addition, observations of f o F 2 from the vertical ionosondes at Beijing, Changchun, Qingdao, and Suzhou stations are compared with the model prediction of f o F 2 . The results indicate that the developed real-time f o F 2 mapping model based upon genetic algorithm-based NN is very promising for ionospheric studies.

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This paper presents the background features of Schumann resonances (SR) observed at the Yongsheng observatory in Yunnan, southwestern China. We calculated the hourly average of the frequency and power spectral density (PSD) of the lowest three SR modes, and analyzed diurnal variation of SR frequency and PSD both in BNS and BEW components around equinoxes and solstices. Diurnal variation of SR PSD is found to be related to the dominant intervals of Asian, African and American thunderstorm centers and the relative position of the observatory to three thunderstorm centers. Diurnal variation of SR frequency is more complicated. SR frequency and PSD at the lowest three modes around the summer solstice and autumn equinox are more variable than that in the spring equinox and winter solstice. The daily median of SR peak frequency in 2011 shows that seasonal variation of peak frequency is blurry, while annual variation of daily median of PSD shows a clear seasonal variation which resembled half a period of a sine curve and symmetrically distributed about July. The seasonal variation of PSD is in accordance with that of lightning activities. Frequency of the first mode is about at 7.5 Hz both in BNS and BEW components. However, with the higher mode, SR frequency in BNS component is 0.5 Hz larger than that in BEW component. The cause of this frequency shift is not clear yet.

A network communication and recording system based on China-made ARCA SOC and embedded Linux operating system is introduced in this paper. It supports TCP/IP network communication protocol and mass storage medium. It has strong points of self-monitor, low power consumption, high timing accuracy, high reliability of operation, etc. It can serve up to 20 centers real-time waveform data at the same time. It meets not only the requirements of physical networking observation, but also virtual networking observation based on Internet in which real-time data transmission is required. Its ability of field recording also meets the requirements of portable seismic observation, strong motion observation and seismic exploration observation, etc.

The China Seismo-ionospheric Ground-based Monitoring Network in Northern China was established in August 2009, consisting of 5 vertical sounding stations and 20 oblique receiving stations. We analyzed the critical frequency of the F2 region (foF2) derived from vertical and oblique sounding data in this study. Our comparison results indicated that foF2 from vertical and oblique sounding presented very similar annual and semi-annual variation characteristics and along with the change in F 10.7 , the two data both enhanced after 2011. We calculated the root-mean-square error (RMSE), percent deviation (PD), and correlation coefficient ( t) between the two data, which showed good positive correlation in Beijing, Changchun, Suzhou station. Our results also demonstrated that the consistency of vertical and oblique foF2 was better in the summer and equinox than in winter. The correlation on calm days for all stations was better than that in the magnetic disturbance period. Our research reveals that oblique sounding data presents similar change characteristics with vertical sounding data, thus these data can be used to investigate ionospheric phenomena.