最近一次日全蝕發生於2017年8月21日，日全蝕的陰影軌跡由西向東橫跨整個北美洲。日蝕期間受到陰影覆蓋的區域電離層全電子含量(Total Electron Content，TEC)有明顯降低的趨勢，利用全球導航衛星系統(Global Navigation Satellite System，GNSS)計算二維TEC空間分布資料時，可看到隨時間移動的月影軌跡(TEC較低之處)。
本研究使用數值斷層掃描(tomography)演算法，將二維空間分布的電子密度積分值(TEC)重建為三維電離層電子密度分佈形態。因為此日蝕事件覆蓋的空間範圍很大，且沿路上通過之GNSS地面接收站電波射線資料充足，適合利用本研究中所使用的最小約束平方法進行電離層電子密度三維空間分佈反演。本研究使用的斷層掃描方法有不需使用初始猜測值作為背景值的優點，結果顯示能不受到初始猜測值的影響，並有效反演出日蝕對電離層造成的電子密度空間擾動變化情形。利用事件天(8月21日)與參考天(8月20日)兩日反演的結果進行分析，結果顯示與過去研究中的觀測相近，且能看到擾動發生時帶電粒子在垂直方向上的變化，如日蝕時來自電漿球層的電漿傳輸通量與日蝕過後帶電粒子的增加主要是來自下層的光化學游離作用。
此方法需要大量的觀測資料，若資料量不足的情況下，三維空間上的解析度將變得不精細，因此較適合重建大規模尺度電離層擾動事件的三維斷層掃描結構。

The ionosphere responses to the total solar eclipse occurred on August 21, 2017, with its shadow traveling across North America from West to East coasts. During the eclipse, the ionospheric total electron content (TEC) is significantly reduced. However, the three-dimensional ionospheric perturbation during eclipse is less studied. In this study, we use the constrained least-squares method to reconstruct the two-dimensional total electron content data into a three-dimensional ionospheric electron density distribution. The tomographic method used in this study has the advantage of not using the initial guess value as the background value, and successfully calculates the spatial disturbance of the electron density caused by the solar eclipse to the ionosphere.
Analyzing the tomographic results of the eclipse day (August 21) compared with the reference day (August 20), we can see the eclipse driven ionospheric plasma transport in the vertical direction showing the downward plasma fluxes from the plasmasphere which alleviate the effects of eclipse induced ionospheric electron density reductions. It is then followed by the post-eclipse increase of the electron density which is mainly produced by the intensified photoionization of the lower part of the ionosphere.

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