全球定位系統(Global Positioning System, GPS)由於具有全球長時間觀測、高時間與空間解析度之優點，因此適合用來觀測大規模之電離層變化。國際參考電離層(International Reference Ionosphere,IRI)是世界上研究電離層的專家們最常使用來推導各項電離層參數的電離層模式。本論比較1997和2000年GPS觀測與IRI模擬電離層全電子含量(Total Electron Content, TEC)之赤道異常峰，有以下發現： 異常峰TEC強度在春秋兩季均比夏季來的高。這是因為電離層裡的中性大氣尺標高（scale height）在日照點附近因溫度較高而加大，使得電離子與中性大氣的碰撞機率加大，加速電子的消失，進而導致TEC之減小。異常峰在冬季出現的時刻最早，夏季最晚，而2000年又比1997年要晚了一些。赤道異常峰所出現的緯度在冬季會偏向磁赤道，在其他季節則會偏向較高的緯度，這可能是在日照比較強烈時，噴泉效應較為顯著，使得電子被帶往較高的地方，再順著磁力線往南北方向傳輸至較高的緯度。1997年GPS模擬與IRI觀測的TEC強度均比2000年小，顯示太陽活躍度會促使TEC增強。此外1997年北半球IRI模擬TEC強度比GPS TEC為大，經由與交通部電信總局電信訓練所中壢電離層觀測報告之ypF2比較發現IRI對此一厚度的模擬會有偏高的趨勢。 The global positioning system (GPS) is an ideal tool to be employed to observe a large scale of ionosphere for its high spatial and temporal resolutions. The International Reference Ionosphere (IRI) has been widely used standard for the specification of ionospheric parameters. In this study, the total electron content (TEC) crest obtained form measurements of ground-based GPS receivers are compared with those in derived from IRI in year 1997 (solar minimum) and 2000 (solar maximum). Both GPS observations and IRI-2000 results show that the crest TEC values in spring and autumn are greater than those in summer and winter. The locations of TEC crest will approaches geomagnetic equator in winter and moves toward the poles in other seasons. TEC crests appear earliest in winter and latest in summer during a year and occur earlier in 1997 than those in 2000. YpF2 is the semi-thickness of the F2 layer deduced from a parabolic fit to the ‘nose’ of the electron density distribution with hight and based on the observed h’f trace. The ypF2 derived from the IRI electron density profiles are also compared with those from the report of of ionospheric characteristics and f-plots at Chung-Li .
