從台南成功大學裡航太場接收站(東經120.2774度,北緯22.7993度)接收GPS衛星上的導航訊息與訊號振幅值，利用這些資料可以算得衛星與台南接收站的相對即時位置與仰角。此研究統計了2003年到2007年這些資料，從訊號振幅值算出S4的大小，在與算出來的GPS衛星軌道位置做結合，投影在350km的高度就可以了解不規則體的發生的位置。再利用仰角簡易來判斷該S4是否屬於電離層或是對流層所發生的閃爍。由於赤道區與中緯度區的不規則體形成機制不同，推論其S4會滿足不同機率分佈函數。也針對本地時間與2003年到2007年各月的S4機率分佈圖，發現S4出現分別在日落過後和午夜之前。S4在各個經緯度上的機率分佈情形。藉此我們可以看出S4大小在時間上與經緯度上的變化。 The GPS signals received by high resolution GPS receiver located at Tainan from 2003 to 2007 were analyzed, in which 3-minute scintillation signals of the GPS amplitude variations were employed to estimate S4 index. The elevation angle and trajectory of GPS satellite were both computed to locate the electron density irregularities responsible for the S4 index. Combining satellite orbit projected at 350km and S4 index, the location of the ionospheric irregularities can be identified. The characteristics of the scintillations induced by refractivity fluctuations in troposphere and ionosphere were investigated. We find that the statistical properties of the S4 index originated from troposphere and ionosphere are very different. The ionosphere-originated scintillation generally started to occur in 1 hour after sunset, appeared most frequently just before local midnight, and disappeared by early morning. However, the troposphere-originated scintillation occurred nearly uniformly throughout 24-hour a day.
