散狀F層（spread F）是一種存在於電離層F層中的電漿不穩定現象，其發生會受電漿漂移、中性風等因素的影響。本篇論文利用全球定位系統與電離層探測儀，研究1999年4月至2000年3月（太陽活動極大期），南美洲磁赤道地區之散狀F層現象。研究方式是以電離層探測儀之觀測結果判斷散狀F層的發生（ISF），並以其為基準，比對黃昏時垂直向上的電漿漂移速度（V ）、電離層F層最大虛高（h''Fmax）、赤道異常現象的對稱性（Ia）、GPS相位擾亂（Fp）以及地磁擾動（Kp）等參數的相關性。結果顯示V 對於ISF發生機率有正向的貢獻，Ia對於ISF發生機率有反向的影響。ISF現象與Fp會隨著V 的增加而增強。另外，ISF發生機率和Fp在春秋季會隨著Kp增加而遞減，但Kp對於V 、h''Fmax以及Ia的影響並不顯著。

Equatorial spread F (ESF) is one of pronounced plasma instability features appearing in the ionospheric equatorial F region, geomagnetic. Previous studies show that the ESF occurrence is mainly affected by the E?B drift and transequatorial thermospheric wind. In this study, the ESF observed by a digisonde termed “Ionogram Spread F (ISF)” at the west side of South America during the solar maximum period of April 1999－March 2000 is examined. The ISF occurrence is compared with the E?B drift (V?), the greatest value in the minimum virtual height of the F layer (h’Fmax), the asymmetry of equatorial ionization anomaly (Ia), GPS phase fluctuation index (Fp), and magnetic activity index (Kp). The results show that V? initiates ISF, while Ia suppresses ISF. As V? becomes larger, ISF gets more spread and Fp tends to be larger. Furthermore, the occurrence probability of ISF and Fp decrease when Kp increases during equinoctial months. However, there is no clear evidence to support that Kp influences V?, h’Fmax, or Ia.

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