學者普遍認為風切理論是形成Ｅ域電離層離子層最可能原因。Larsen [2002]相信大 的風切將能引起 KH（Kelvin-Helmholtz）不穩定，並而且認為隱埋在整個風切擾動的 翻滾結構，是造成雷達偵測到類週期性回波(quasi-periodic)的原因。Bernhardt [2002]的 數值模擬顯示，即使採用相對於 KH風切小的起始擾動，受到電漿翻滾作用後，將使 120與 100公里高度的離子層演化成團狀或傾斜排列的層狀結構。Choudhary et al., [2005] 分析 Gadunki 雷達，QP 回波的都卜勒速度、回波功率及頻譜寬隨時間的變化， 概念上合理的說明顯示在 RTI圖，傾斜條狀(斜率為負)，涵蓋高度範圍 5-10公里，是 由 KH波浪所造成的雷達回波結果。本計畫將參考 Choudhary et al., [2005]的方法，加 上雷達干涉方法重建回波三度空間結構的功能，比較分析特高頻雷達在中壢與南部偵 測到 QP 回波的特性，並探討與 KH不穩定的相關性。 The most likely theory to explain the mechanism of forming dense ion layer in ionization E region is the neutral wind shear theory. Larsen [2000] determined that strong shear appear in the neutral winds were sufficiently large to trigger the Kelvin-Helmholtz (KH) instability and that these could be at the origin of quasi-periodic (QP) echoes that detected by radar. The numerical simulation of Bernhardt [2002] demonstrated that even weak KH turbulence can produce noticeable clumps and tilts structures in height 120 and 100 km, respectively. Analyzing the backscatter QP echoes over Gadanki radar, the time variation of Doppler velocity as well as the power (or spectral width), Choudhary et al., [2005] postulate that the KH billows themselves are triggered by a shear instability in the large ambient zonal wind. In this proposal, data process will refer that reported by Choudhary et al., [2005] on the QP echoes that detected by Chung-Li VHF radar in the Chung-Li station and in south of Taiwan to compare the properties of them. Radar interferometry will provide detail information of resolving spatial structures. Also, the connect relationships between QP echoes and KH instability will be discussed.
