日出前及日落後電離層高度變化之研究

Ionospheric variation in presunrise and postsunset period

鍾鼎國(Ting-Kuo Jung)

指導教授 ： 劉正彥

國立中央大學/地球科學學院/太空科學研究所/博士(2006年)

摘要

摘 要
利用全球電離層觀測站所測得之電離層參數，比較及分析不同經緯度之高層及低層電離層高度及電子濃度，發現電離層高層普遍存在日出前及日落後之高度抬升現象。針對日出前層峰高度之變化和太陽黑子數、中性風、地理及地磁緯度與磁傾角等影響電離層之機制，做進一步之探討，發現日出前抬升(PSL)現象之地理對稱性較地磁及磁傾角對稱性明顯，而與太陽活動性無關，進而由分析資料推斷 PSL 在磁赤道附近應以東西向電場的貢獻為主，其它地區則主要受子午向中性風所控制。對於日落後高層電離層之抬升現象，經由分析資料驗證應為日落後東向電場反轉前增強所造成，其範圍不局限在磁赤道地區，且與太陽黑子數呈正相關。本論文亦對低層電離層之電子濃度及高度作一比較及分類，藉由對各層之認識以了解影響電離層之動力機制。

關鍵字

太陽黑子 ； 子午向中性風 ； 電離層F層虛高 ； 電離層散塊E層虛高

並列摘要

Abstract
Examining the parameters foF2、 h''F、 foEs and h''Es recorded by ionosonde to study the diurnal、 seasonal、latitudinal and solar activity variations in heights and plasma frequencies. The results show that foF2 yields maximum values at the two equatorial anomaly regions. The minimum values in the northern and southern anomaly regions appear in summer and winter, respectively. In general, the foF2 value is in proportion to the sunspot number.
It is found that there are always exist ionospheric height lift in pre-sunrise and post sunset periods at higt attitude and h''F lifts in its attitude during pre-sunrise and post sunset periods. For the latitudinal distribution the pre-sunrise covers a greater range in southern hemisphere than in northern. Moreover, the pre-sunrise lifts in the northern and southern reach their maximum va1ues in winter and spring, respectively.
The lifts of the post sunset appear mainly in stations HU、VA and TT of the southern hemisphere. The most clear signatures usually found in summer. The lift in altitude is also in proportion to the sunspot number.
The foEs value in northern hemisphere is possibly greater than 5MHz. No obvious relationship can be found between foEs value and sunspot. h''Es lifts its altitude simply during morning period in winter and early spring and during both early morning and afternoon periods during late spring-fall. The lifts increase while the latitude decreases in the northern hemisphere. However, there is no latitudinal and solar activity effect found in the southern hemisphere. Finally, the lifts signatures in h''F and h''Es indicate that the E × B vertical drift and Zonal/meridional wind plays an important role.

並列關鍵字

sunspot number ； h''F ； h''Es ； meridional wind

參考文獻

Abdu, M. A., J. H. Sobral, P. Richard, Marta. M. degonzalez, Y. N. Huang, B. M. Reddy, K. Cheng, E. P. Szuszcewicz, andI. S. Batista. Zonal/meridional wind and disturbance dynamo electric field control of the low-latitude ionosphere based on SUNDIAL/ATLAS 1Campaign, J. Geophys. Res., 101, 26729-26740, 1996.

Aggson, T. L., F. A. Herrero, J. A. Johnson, R. F. Pfaff, H. Laakso, N. C. Maynard and J. J. Moses, Satellite observation of zonal electric field near sunrise in the equatorial ionosphere, J. Atmos. Terr. Phys., 57, 19-24, 1995.

Behnke, R. A., M. Kelly, G. Gonzales, M. and Larsen, Dyanmic of the Arecibo ionosphere：A case study approach, J. Geophys. Res., 90, 4448-4452, 1985.

Biondi, M. A., J. W. Meriwether, Jr., B. Fejer, and R. Woodman, Measurement of the dynamics and coupling of the equatorial thermosphere and F-region ionosphere in Peru, J. Atmos. Terr. Phys., 50, 937-942, 1988.

Bunside, R. G., R. A. Behnke, and J. C. G. Walker, Meriduonal neutral winds in the thermosphere at Arecubo ：Simultaneous incoherent scatter and airglow observation, J. Geophys. Res., 88, 3181-3189, 1983.