日落反轉增強 (prereversal enhancement, PRE)發生於赤道電離層之黃昏時段，其垂直電漿飄移由原先微小值，突然轉為強烈之向上飄移現象。本篇論文利用美洲和亞洲/大洋洲兩經度鏈之全球定位系統 (Global Positioning System, GPS)地面接收機資料，逐日探討2002和2009年日落反轉增強引發之電離層全電子含量緯度分佈和日變化，而其季中位數值將與福衛三號探測電子濃度相互比較。結果顯示，日落反轉增強影響之全電子含量，春秋分大於夏冬至，太陽活動極大期大於極小期；緯度分佈，春秋分比冬夏至遠離赤道區，太陽活動極大期比極小期遠離，增強現象最常發生於2100LT。此外，相位擾亂(phase fluctuation)值正比於對應之全電子含量，說明日落反轉增強對電離層不規則體之發生有正面之貢獻。

The prereversal enhancement (PRE) in the vertical ion drifts is a particularly well known low latitude electrodynamic feature, exhibited as a sharp upward spike in the velocity shortly after local sunset, which would result in plasma density increases in the off-equator areas. In this study, to observe signatures of the PRE, total electron contents (TECs) derived from GPS ground-based receivers and electron density derived from FORMOSAT-3/COSMIC of two chains along the American longitude of 70°W and Asian/Australian longitude of 120°E are used. We compute the associated strength and occurrence frequency of the PRE of the two chains as function of location (geomagnetic latitude), season, and solar activity (2002 and 2009) on GPS TEC and location, altitude, and season on FORMOSAT-3 / COSMIC electron density. Results show that TEC and electron density increase associated with the PRE are more pronounced in equinox (solar maximum) than solstice months (solar minimum). Finally, FP values can also be seen to show a linear relationship with TEC and electron density increase associated with the PRE.

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