臺灣博碩士論文加值系統

摘要
過去動態式電離層觀測儀，回波方位觀測受到Fresnel scale 的限制，最小只能觀測到幾公里的不規則體尺度 ，無法看到一公里以下小尺度的不規則體變化情形。而在本文，藉由全反射回波時間上的相位變化與空間的關係，建立相位變化的的結構函數（structure function），所謂的結構函數，是指統計上的隨機統計特徵值，其相位均方差(mean square difference)的值。然後我們再利用已知結構函數 與時間間隔的指數關係圖中的斜率（SIB）與波譜指數ν在2.2＜ν＜2.6時，有著SIB=0.936ν-0.97的關係式。來反推不規則體的波譜指數（spectrum index）。藉由不規則體的波譜指數對時間的分佈圖，來推測不規則體小尺度的變化情形。並由得到的數天觀測結果了解下列結論：1.實際觀測所得結果與模擬的結構函數結果相符2.所得觀測尺度之波譜指數ν值分佈均介於2∼3之間。

Abstract
The relevant irregularity spatial domain extends from decameter radio wavelengths to the first Fresnel scale, a few kilometers, using Dynasonde to measure .We present , however, a new approach to investigating ionospheric irregularities, using the temporal structure function of totally reflected radio echo phase variations. We obtain a theoretical relation of both the direct and inverse problems. Although long-period phase measurements are practicable and essential to exploring larger irregularity scales, they require observing modes dedicated to multiple fixed-frequency time series, and this undesirably limits the number of altitudes that can be monitored simultaneously. In consequence, we established a structure function by phase variations.The structure function is one of the common statistical characteristics of a random field. Astructure function estimate is defined as the mean square difference of the field values taken at pairs of locations or times. And we use the relationship between the slop of structure function and spectrum index to calculate small-scale irregularity spectrum index.

目錄
第一章前言
1.1研究動機…………………………………………………………5
1.2電離層簡介………………………………………………………8
1.3電離層不規則體觀測歷史簡介…………………………………11
第二章動態式電離層探測儀(Dynasonde)
2.1動態式電離層探測儀的發展歷史簡介…………………………14
2.2雷達系統介紹……………………………………………………16
2.3動態式電離層探測儀的基本觀測原理…………………………19
2.4動態式電離層探測儀所得電離圖簡介…………………………25
第三章結構函數的理論建立
3.1動態式電離層觀測儀應用於不規則體的限制…………………28
3.2動態式電離層觀測儀於小尺度不規則體觀測的基本假設……30
3.3回波相位頻譜分析………………………………………………32
3.4結構函數的數學推導……………………………………………35
3.5結構函數理論上的推估…………………………………………40
第四章實驗與模擬
4.1雷達相位資料分析………………………………………………44
4.2回波相位結構函數之估計………………………………………47
4.3全天候觀測結果…………………………………………………52
第五章結論與展望……………………………………………………62

圖表目錄
圖1-1典型電離層電漿密度隨高度分布圖………………………………10
圖2-1中壢雷達硬體簡圖…………………………………………………18
圖2-3電離層觀測圖………………………………………………………27
圖3-1繞射條紋與鑑別率的關係…………………………………………28
圖3-2 Fresnel　Zone與距離的關係……………………………………29
圖3-3凍結的不規則體運動示意圖………………………………………31
圖3-4對數振幅的功率波譜………………………………………………34
圖3-5發射電波與地磁角度、不規則體運動速度的幾何示意圖………36
圖3-7相位結構函數的模擬結果…………………………………………41
圖3-7在對數座標下相位結構函數與波譜指數的關係…………………42
圖3-8理論上模擬波譜指數與結構函數斜率ＳＩＢ關係圖……………43
圖4-1 Beal Lake，2001年5月3日電離層全天候觀測圖……………46
圖4-2（a）Bear Lake 20010503，14:15之電離圖……………………48
圖4-2（b）動態式電離層觀測儀由（a）圖中得到回波相位資料的前置處理……………………………………………………………………48
圖4-3結構函數圖形………………………………………………………49
圖4-4結構函數處理步驟之流程圖………………………………………51
圖4-5（a） 0點55分的電離圖、資料處理與結構函數…………53∼57
圖4-6 2001年五月3日全天200公里∼400公里，5∼6MHz之波譜指數對時間關係圖 ………………………………………………………58
圖4-7 2001年四月3日到五月20日波譜指數對時間關係圖……59∼61
圖5-1以頻率做區別的波譜指數對時間關係圖…………………………66
表3-1飄移速度V和發射信號與地磁夾角 ，分別對數相位結構函數 之y軸截距SIA　的關係…………………………………………41
表3-2不規則體飄移速度V和發射信號與地磁夾角 ，對數相位結構函數 之斜率SIB　的關係…………………………………………41
表3-3光波指數ν與對數相位結構函數 之斜率SIA、截距SIB的關係……………………………………………………………………42

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