| 摘要: | 本篇論文利用全天式影像儀研究電離層不規則體。全天式影像儀用以觀測夜間之大氣暉光，且可觀測到大尺度的不規則體，即赤道散狀F層。整個觀測系統分別架設在印度的Kavalur (12.5N, 78.8E, 地磁緯度：4.6N) 與台灣的鹿林山 (23.47N, 120.87E, 地磁緯度：13.45N)。全天式影像儀所觀測的大氣暉光波長選定在630.0奈米、557.7奈米以及777.4奈米，因為不同的大氣暉光波長會顯示出大氣暉光耗損不同的特徵。在進行大氣暉光觀測的同時，觀測地附近的電離層探測儀也被用來量測電離層的最低高度，並記錄當大氣暉光耗損存在時，散狀F層是否出現。 印度地區的觀測結果顯示了許多大氣暉光耗損新的特徵。其中包括新形態的大氣暉光耗損：首先，兩條暗帶在儀器視野北邊連結而形成反V的分叉，接著完全結合在一起。此外還包括子夜後在儀器視野中形成的630.0奈米大氣暉光耗損，以及自儀器視野的北方進入的塊狀630.0奈米大氣暉光耗損。最後，許多的557.7奈米大氣暉光耗損也經常性的出現在觀測影像上。因此，論文中詳細探討大氣暉光耗損結合時的電離層狀態，以及其在子夜後之發展。結合不規則體沿磁力線映射的特徵與630.0奈米大氣暉光的發光機制與高度之關係，可解釋大氣暉光耗損出現在全天式影像儀的視野北方邊界之原因。論文中也利用數值模擬解釋電離層的狀態如何影響557.7奈米的大氣暉光耗損在不同時間與太陽活動性的變化。在台灣的鹿林山，新建立的全天式影像儀於2006年8月進行觀測。而觀測結果發現台灣上空有電離層行進式擾動通過。而本論文也探討了相關的物理現象。 This dissertation focuses on the study of ionospheric irregularities using selected airglow emissions whose intensity is related to plasma density. All sky imaging technique is used to observe the large scale ionospheric structures, known as plasma depletions, which are often associated with Equatorial Spread-F (ESF) phenomena. The experiments conducted from Kavalur (12.5N, 78.8E; 4.6N geomagnetic), India, and Mt. Lulin (23.47N, 120.87E; 13.45N Geomagnetic), Taiwan are used in this work. The 630.0, 557.7, and 777.4 nm emissions are used for recording the images. The different emissions reveal different characteristics of depletions. The ionosonde data is used to monitor the base height of the F-layer as well as the presence or absence of Spread-F at the time of the appearance of depletions in all sky images. Several new features of plasma depletions are revealed in this study such as the new type of ‘joined’ pair of depletions where the northern (and later the southern) ends join together, producing an inverted ‘V’ shape bifurcation, which later merge together, sequences of depletions developing in the field of view of the all sky imager in the post-midnight period, depletions in 630.0 nm images entering the field of view (FOV) as dark patches from the north end in the post-midnight period, and the frequent observations of plasma depletions in 557.7 nm images. The ionospheric conditions resulting in the joining and merging of depletions, and the post-midnight development are discussed. The field aligned mapping of irregularities together with the altitude dependence of the 630.0 nm emission is proposed to be responsible for the 630.0 nm depletions to appear as dark patches at the northern ends of the FOV. A simulation is carried out to understand the important physical parameters that influence the emissions of the 557.7 nm in various local times and solar activities, and result in the appearance of depletions in the integrated images. An all sky imager has been designed and developed at the Institute of Space Science, National Central University, during the course of this dissertation. The imager was operated from Mt. Lulin, during the new moon periods since August 2006 to study the large scale ionospheric structures. The optical signatures of traveling ionospheric disturbances (TID’s) detected during this period are described. These observations are also used to understand the nocturnal variation of airglow intensity over Taiwan in different wavelengths. |
