Comparative Study Of Polar Ionospheric F Layer Observations With IRI In Both Hemispheres

Based on the good geographic locations of magnetic conjugate between Chinese Zhongshan Station in Antarctic and Svalbard Station in Arctic, with the convenient share of International Polar Year (IPY, 2007-2008) radar data, the characteristics of F layer ionosphere in both hemispheres are compared. It is helpful to understand ionosphere structure and formation mechanism. Further more, the data obtained from both DPS in Zhongshan and incoherent scatter radar in Svalbard are compared with that predicted by the latest International Reference Ionosphere model, IRI-2007, which can evaluate IRI-2007's forecasting capability so as to help improve its accuracy in polar regions.Firstly, This paper analyzes the changing characteristics of ionosphere in Zhongshan and Svarbard by using the respective observation data. The diurnal variation of F2 peak parameters foF2 and hmF2 is analyzed and their formation mechanism is discussed. The IRI-2007 forecasting results are compared with the observation results, and IRI model condition in polar gap ionosphere is introduced. In this paper, the North and the South Geomagnetic conjugate observation of the two stations compared with the IRI model results show that, IRI model application in the polar regions need to be further improved and also give suggestions. The main work of this paper can be concluded as follows: 1. The study on diurnal variations of F layer ionosphere in both Antarctic and Arctic As for foF2, there are magnetism noon phenomena in the autumn of Zhongshan and Spring of Svalbard. And at equinox, the changing range is much bigger than in the other seasons. Summer's diurnal variation is relatively gentle with small changing range. There is double-hump structure in winter. In Zhongshan, the highest peak appears at magnetism noon, the second highest peak appears around 1700MLT; while in Svalbard, there are no peak value around the magnetism noon but at 08MLT and 18MLT and these two peaks are quite close in value. On the whole, the foF2 in Zhongshan is bigger than in Svalbard. It has nothing to do with solar F10.7 radiation flux. It indicates that the major peak in Zhongshan is relevant to solar-ionized high-density plasma in low-altitude zones passing through polar gap; while the F layer in Svalbard is relative to the auroral particle precipitation.As for hmF2, at equinox, the diurnal variation has an asymmetric"W"shape, whose changing range is much wider. The changing range in summer is relatively small and smooth. And compared with other seasons, the hmF2 in Zhongshan and Svalbard are much similar in shape, yet the average height of Zhongshan is higher than that of Svalbard.2. The study on comparison between observations and IRI in both Antarctic and Arctic.In summer, the foF2 observations in Zhongshan and Svalbard fit the IRI model much better. It is possibly explained by the reason that the IRI model is largely based on the observations at lower altitude which best consider the solar radiation. Similarly, in polar zone the sun is most active in summer and plays a vital part in affecting the ionosphere environment. In winter, the comparison result is the worst. IRI model can not reflect the change of peak value after the noon. It because the sun is always under the horizon for most of time in winter which results in the lack of solar radiation. The auroral particle precipitation is mostly affecting the F layer at equinox and in winter, but not well included in the IRI model. Besides, the hmF2 forecasted is larger than the observations.3. Advice for improving the IRI model to apply to the polar regionThe particular module is needed to describe the ionosphere in polar region under the influence of particle precipitation and plasma convection. As an empirical model based on observation data, more observation stations in polar region are in great need so as to better the IRI model by providing more convincing record.