由於現今太空科技的發展，以及太空觀測儀器的進步，使得我們可以更容易得去探討有關於太空的物理現象以及相關機制，也因於人們更依賴太空科技所帶來的便利性，各國所投入發展太空科技的金錢日益漸增，為了避免太空天氣的危害導致經濟龐大損失，太空天氣的研究將更加被重視。本論文分析了當太空天氣造成磁層擾動時，磁尾處偶極化區之電子拋射角分佈特徵的改變，並詳加探討。
有關於電子拋射角的相關研究，目前由文獻可了解到絕熱費米加速機制可造成電子拋射角分佈演進成雪茄型的分佈，以及貝他加速機制可造成電子拋射角分佈演進成鬆餅型的分佈，但是尚還有些情況還需要其他的機制才有可能的去解釋所有觀測到電子拋射角特徵，往後還需要研究人員從此去深入探討。
本論文使用西密斯衛星於2008年至2011年間的探測資料，其中包含了2008年至2009年間的42個偶極化事件資料（Wang et al., 2014），利用統計分析的方式分別去探討磁層擾動發生時，電子拋射角分佈特徵之演進，電子拋射角分佈變化特徵與離地心之徑向距離之相關性，電子拋射角分佈變化與場線長度之相關性，電子拋射角分佈變化與偶極化角變化之相關性。

In this thesis, radial dependence of variations in anisotropies for pitch angle distributions (PAD) of electrons at the dipolarization sites in the Earth’s tailside is investigated through statistical analysis on observations of THEMIS (Time History of Events and Macroscale Interactions during Substorms) mission from the year of 2008 to 2011. The data of electrons with energy ranges from a few eV to MeV detected by the charged particle instruments on THEMIS probes, the electrostatic analyzer (ESA) and the solid state telescope (SST), are adopted. The primary focus is on how the anisotropy ratio between the dipolarization period and before the dipolarization starts distributes with L-shells and field line lengths the THEMIS probes located. The results show that a specific dependence feature does exist for the energy range around a few keV and possible theoretical interpretations are discussed.

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