在赤道地區日落後電離層F 層，因為突增的東向電場(Eastward
Electric Field)，造成垂直上昇漂移速度(Vertical Drifts)的增大，使得電離層F 層向上抬升，讓不規則體產生的機率提高。
我們利用中華衛星一號上的電離層電漿電動效應儀(IPEI)所量測
到的離子資訊，從2000 年2 月份到2004 年1 月份，取出K p<3 的資料，分成3 個當地時段(Local Time) ，在赤道地區對日落後的不規則體發生的機率特性，隨著經度、當地時間以及季節的變化，與其相對應的垂直上昇速度作一系列的相關性研究。觀測結果發現，在日落後其當地時段(18 LT ~19 LT)的垂直上昇漂移速度突增，與不規則體的產生有很大的相關性；而且磁偏角會影響到四個季節的垂直上昇漂移速度的變化，所以也會造成在其相對應的季節有不同的不規則體的產升機率。

Large vertical drifts driven by eastward electrical fields appear in the post-sunset equatorial F region. These enhanced vertical drifts drive the ionospheric F region to high altitude and results in many scintillation-producing irregularities from February 2000 to January 2004.We also use the ROCSAT-Ι data to obtain vertical drifts in three separate 16:00~19:00 local time regions when the geomagnetic Kp index is smaller than 3. The correlation of the post-sunset equatorial irregularity occurrences and the vertical drifts is studied with different of LT regions,geographic longitudes,and seasons. From our study,we found that the vertical drifts increase rapidly at the post-sunset of 18LT~19LT and have a good correlation with vertical drifts. Furthermore,we found
the magnetic declination affects the vertical drifts ,and it leads to a better correlation with the irregularity occurrence with the vertical drifts for all seasons.

Davies, K., Ionospheric Radio, Short Run Press Ltd., Exeter, England,1990.
Farley, D.T., Bonelli, E., Fejer, B.G. and Larsen, M.F. The prereversal enhancement of the zonal electric field in the equatorial ionosphere. , J.Geophys Res.,1986
Kelley, M.C., The earth’s ionosphere,Plasma Physics and
electrodynamics,publish by ACADEMIC PRESS LIMITED,1989
江峻毅，中華衛星一號觀測電離層較大電漿氣泡在季節及經度之統計與研究，碩士論文，國立中央大學太空科學所，2004
參考網站
http:/csrsddc.csrsr.ncu.edu.tw/IPEI_DESC/ipei_intro.html
http:/www.new.ss.ncu.edu.tw/~lyu/lecture_files/introspace.html