A Study On Local Ionospheric Model Of Total Electron Content Over Wuhan

Total electron content(TEC), as a very important ionospheric parameter,plays a significant role in correcting the errors of transionospheric radiopropagation and theoretic research of the ionosphere. Using the TEC dataobserved at Wuhan Ionospheric Observatory for a solar cycle (from 1980 to1990), we discuss the features of TEC and TEC modeling.TEC has significant characteristics in diurnal and seasonal variation. Andthe variation of TEC during a solar cycle shows very good correlationrelationship with solar 10.7cm flux index. On the basis of this correlation, anempirical TEC model is constructed. In this model, we apply a linear functionto describe the relationship between TEC and solar 10.7cm flux index, and takeFourier series analysis to investigate the diurnal and semidiurnal variations ofTEC over Wuhan. The agreement between the predications of our model andthe observed TEC data at Wuhan is quite satisfactory: the basic trends and thediurnal variations are well reproduced. The model predication error is smaller inthe years with low solar activity than in those with high solar activity, smaller inwinter and summer than in spring and autumn, and in the morning and at nightthan in the day time and in the evening. Compared with International ReferenceIonosphere (IPI), our model is more accurate in predicting TEC over Wuhan.Using the same method, we model the parameter foF2 and M(3000)F2 quitewell. And then the peak electron density of F2 layer (NmF2) can be calculatedfrom foF2. By series analyzing, the relationship between TEC and NmF2i.e.foF2 is testified. Using their empirical connection, we obtain the scale heightof Oxygen atom. Similarly, the peak height of F2 layer(hmF2) can be calculatedfrom M(3000)F2. A supposing that the height distribution of electron densityfits Chapman function, we model the N_e profile by inputting the modeled NmF2,hmF2 and H_o. And then the electron content with height in some rangecan be attained using the profile.By integrating the continuity equation for electron, we deduce the TECcontinuity equation. And then we calculate the total electron content bysimplifying the equation through Chapman function. The primary shape of TECis matched, but the semiannual and seasonal variations especially wintermaximum not well represented. On the other hand, we calculate thetransportation term by importing the observed TEC. The magnitude of the termis about 10¹⁴m^-2s^-1 in high solar activity year, while 10¹³ m^-2s^-1 in low solaractivity year. And in the day flux is upward in summer while downward inwinter, the flux is downward in all season at night.In conclusion, we have described the characteristics of total electron contentmeasured over Wuhan, which is the basis of our modeling research on TEC.The method is also applicable to two other important parameters foF2 andM(3000)F2.The TEC continuity equation is concluded and its application isprimary discussed, which is useful for the theoretical modeling of TEC.