| DC 欄位 |
值 |
語言 |
| DC.contributor | 電機工程學系 | zh_TW |
| DC.creator | 劉彥宏 | zh_TW |
| DC.creator | Yen Hung Liu | en_US |
| dc.date.accessioned | 2013-6-4T07:39:07Z | |
| dc.date.available | 2013-6-4T07:39:07Z | |
| dc.date.issued | 2013 | |
| dc.identifier.uri | http://ir.lib.ncu.edu.tw:88/thesis/view_etd.asp?URN=945401001 | |
| dc.contributor.department | 電機工程學系 | zh_TW |
| DC.description | 國立中央大學 | zh_TW |
| DC.description | National Central University | en_US |
| dc.description.abstract | 本論文修改Wernik所提出建構訊號閃爍分布之方法獲得以華衛一號衛星所量得電離層的離子密度為基礎的赤道區不同季節變化的訊號閃爍分布模式。此獲得訊號閃爍模式的方法以最佳化可靠區原理為基礎，對所獲得離子密度頻譜進行最小平方差曲線比對，以獲得頻譜參數：頻譜斜率及最大尺度。在弱閃爍條件下(S4<0.3)，我們獲得的S4分布與過去文獻發表的結果相近。然而當閃爍程度加強(0.3< S4<0.6)，S4在緯度上的分布則移至赤道異常區。此外本論文所獲得的最大尺度分布對於研究不規則體的演化具有頗大助益。我們進而討論訊號閃爍分布隨不同參數的改變，其中影響的參數包含地磁緯度、地球經度、本地時間、太陽活動及地球磁場變化。
除此之外我們以一組特殊量測資料作詳細電波通過電子不規體而產生閃爍現象的研究。此資料為在西元兩千年三月二十四日晚間同時獲得Ascension Island地面閃爍訊號及ROCSAT-1衛星量測到太空不規則體離子密度資料。首先我們對地面閃爍訊號進行統計分析，其結果顯示Nakagami分布可以用來描述S4大到1.4的L-Band閃爍訊號。其次由於多重反射的效應，在弱閃爍條件下所預測S4與頻率的相關趨勢也不成立，對地面閃爍訊號進行頻域及時域分析發現VHF訊號比L-Band訊號承受較嚴重多重反射效應的影響。進而我們對所量測到的離子濃度及地面閃爍訊號加以比對並研究兩者變化的關係。結果離子濃度與閃爍訊號的因果關係在部分資料內可觀察到。最後以PEM數值模擬方式執行閃爍訊號數值模擬和Ascension Island量測資料進行比對，藉以驗證此同時量測到太空及地面量測資料的事件確實發生。 | zh_TW |
| dc.description.abstract | The global/seasonal/local-time distributions of scintillation occurrence rate have been obtained from the in-situ density measurement of ROCSAT-1 during moderate to high solar activity periods of 2000 to 2003. The scintillation was obtained with a modified procedure of the thin-phase screen model of Rino reported in Wernik et al. [2007]. The distribution of the S4 index for the weak scintillation (S4<0.3) is almost identical to that of the equatorial irregularity distribution reported in the literature. However, as the scintillation level increases (0.3< S4<0.6), the latitudinal distribution moves to the equatorial ionization anomaly (EIA) region. In addition, the distributions of the outer scale values that are valuable for the study of physical evolution of the irregularity structure are also obtained. The occurrence distribution of scintillation activity with several parameters such as dip-latitude, longitude, local time, solar activity, and geomagnetic activity during different seasons are presented and discussed in the report. In addition, a special case of coincident observation that occurred on 24 March 2000 between the irregularity structure measured by ROCSAT-1 and the scintillation experiment at the Ascension Island has been studied. The study of scintillation statistics is carried out first and the results shows that the Nakagami distribution can portray the scintillation intensities with S4 up to 1.4 for the L-band scintillation. Moreover, the departure of frequency dependence of S4 predicted by the weak scintillation is noticed due to the multiple scattering effect. The measurements between the satellite and scintillation data are then compared against each other to study the similarity in the gross feature between the characteristics of irregularity structure and the scintillation variation. The causal relationship between the fluctuation of ion density and the scintillation variation is obtained. The coincident observations are also validated by the PEM simulation result. | en_US |
| DC.subject | 赤道區不規則體 | zh_TW |
| DC.subject | 訊號閃爍 | zh_TW |
| DC.subject | 最大尺度 | zh_TW |
| DC.subject | S4指標 | zh_TW |
| DC.subject | equatorial irregularity | en_US |
| DC.subject | scintillation | en_US |
| DC.subject | outer scale | en_US |
| DC.subject | S4 index | en_US |
| DC.title | 運用華衛一號資料研究全球低緯區電離層電波訊號閃爍現象 | zh_TW |
| dc.language.iso | zh-TW | zh-TW |
| DC.title | Using ROCSAT-1 In-situ Data to Study the Radiowave Scintillation Phenomenon in the Equatorial to Low-Latitude Ionosphere | en_US |
| DC.type | 博碩士論文 | zh_TW |
| DC.type | thesis | en_US |
| DC.publisher | National Central University | en_US |