Isual Publications 2014

Isual Publications 2014

  • id
  • date time
    2014-04-08 14:38:00
  • 2008
  • 6
  • 周容光(2008),‘藍色及巨大噴流等高空短暫發光現象之探討’,國立成功大學物理研究所(碩士論文)
  • 近幾年來,高空短暫發光現象吸引了許多的注意與研究。當中的噴流事件由於被觀測的次數很少,所以對它們的特性與機制尚未清楚。在2007年7月22日,我們於鹿林觀測站意外拍攝到多個噴流事件,由多波段觀測系統拍攝的影像,確定噴流事件除了發出藍光之外,紅光也占重要的比例。由這個結果,可以證實福爾摩沙衛星二號記錄的藍色發光事件即是blue starter以及藍色噴流。 
    地面觀測的記錄中,有一組噴流事件的序列:首先發生blue starter,並在100毫秒後,在同一雲頂位置發生藍色噴流,更在50毫秒之後發展成巨大噴流。此現象讓我們認為blue starter和藍色噴流是巨大噴流的前導放電過程,如同產生閃電之前的階梯前導。除此之外,我們利用地面觀測所拍攝的連續影像,分析噴流事件與閃電的關聯性,並在噴流事件的周圍一定範圍內,將發生在事件前、後5秒內的所有光學回擊作成累積分布圖。我們發現分布的趨勢除了Wescott et al.在1996年於Geophysical Research Letters發表的結果外,還有其它不同的趨勢,這顯示出發生噴流事件的因素是多樣化的,我們也解釋不同的分布趨勢相對應的物理機制。 
    衛星觀測到的藍色發光事件常在短時間內連續發生,其發生率可高達每2秒產生1個事件。分析光譜後發現blue starter和藍色噴流具有相似的光譜特性,這表示它們的產生機制是相似的。在本文中也整理衛星與地面的觀測資料,發現噴流事件有不同的型態,值得未來更深入的研究與討論。

    In recent years, transient luminous events (TLEs) have attracted much attention and been intensively studied. The electric jet events of TLEs have rarely been observed, so their characteristics and mechanisms are not well understood. On July 22, 2007, we accidentally captured many jet events. The images from our multi-wavelength TLE cameras show that the jet events not only have blue emissions but also contain red emissions. As a result, it is a strong evidence that the blue luminous events (BLEs) recorded by FORMASA satelliteⅡ are blue starters and blue jets. 
    One of the ground observed jet has this event sequence: Firstly, a blue starter occurred, then after one hundred milliseconds a blue jet occurred from the same cloud top. Finally, it developed into a gigantic jet fifty milliseconds later. We suggest that the blue starter and the blue jet could be the leaders of the gigantic jet and they play the roles of the stepped leader in a cloud-to-ground flash. Furthermore, we use the recorded images to look for the relation between the jet event and the lightning activity. The cumulative distribution of optical strokes which occurred around jet events before and after five seconds has been plot. We found that the trends of the cumulative distribution show substantial deviation from those reported by Wescott et al. [1996]. This finding implies that the generating mechanisms of the jet events are much diversified. We also propose the possible physical mechanisms for different cumulative distribution. 
    The BLEs recorded by FORMOSA satelliteⅡ often occur in rapid succession within a few seconds. The occurrence rate can be as high as one event for every two seconds. We analyzed their spectra and found that blue starters and blue jets have similar spectral properties. This means that their generation mechanisms are similar. In this thesis, the data from ground and satellite observations have been carefully analyzed. We found that the characteristics of the electric jet events are multifarious. We hope that our results can be good initialing threads for future studies.

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