電離層中的散塊E層(Sporadic E)簡稱Es，高度大約在90~120公里間，成分除了一些分子性離子外，金屬性離子佔絕大部分。 中緯度Es層的QP( Qusai -Periodic)現象首度被Yamamoto在1991年利用MU雷達觀測到，其後台灣Chung-Li雷達也有接收到QP的回波，但是對於QP的發生卻有各門各派的解釋方法。本篇論文的資料是在1997年8月7日晚上及8月8日凌晨中壢特高頻雷達觀測到的電離層Es層散塊回波，從RTI圖上發現訊號存有準週期回波的特徵，而頻譜圖呈現是屬於型態二梯度飄移不穩定所造成的二次回波。利用雷達干涉法我們可分析不規則體的飄移情形，並在比較各個QP理論後對台灣地區中緯度QP現象的發生嘗試找出合理的解釋。 Sporadic E (Es) layers are ionization enhancements in the E region at altitude between 90 and 120 km. The density can be up to an order of magnitude greater than that in the background and the major species in the layer are metallic. High-resolution observations of quasi-periodic (QP) structures of the midlatitude E region irregularities made with the MU radar were presented in 1991. The structures were found to display striations with periods close to the Brunt Vaisala period. After then, the Chung-Li radar observed the same phenomenon, too. The physical mechanisms proposed for the generation of QP echoes are associated with gravity wave and wind shear. In this study we present an optimum postulate for the QP echoes observed at the Chung-Li VHF radar.
