本研究建立出電離層與外加電流耦合模式，以計算地震前由地殼流入高層大氣之電流對於電離層電子密度、全電子含量、電漿飄移速度等影響。電離層模式基於美國海軍實驗室所開發之三維電離層數值模式SAMI3，並並修改加入地殼驅動之外加電流項。模擬結果指出於當地時間0900~1900輸入強度為1nA/m2，涵蓋範圍120°E±20°,30°N±20°的電流自85公里高流入電離層，將產生約-2.6TECu之電離層擾動，擾動之空間分佈上大致為輸入電流西南側電子含量減少，東南側增加；電流停止輸入後，擾動持續時間大約為5小時，最大電子密度擾動約-7%左右。輸入電流與當地時間關係大致上為傍晚TEC擾動幅度最大；午後的擾動主要為輸入電流西側TEC減少；早晨則相反，位於東側增加較為明顯。另外藉由調整輸入模式不同分量電流模擬，說明平行磁力線分量電流是造成TEC擾動的主要原因。此外透過位能方程式的估計得到兩點結論，第一：擾動電場之空間變化與所輸入的地殼驅動電流密度分佈有關，此方式可以定性地推測出前面模擬中所產生擾動電場的方向、第二：不同當地時間所產生的擾動電場相對大小與沿磁力線積分之佩德森導電率(hight intergrated Pedersen conductivity)大致上為負相關，符合電離層電動效應理論。最後比較由模式底層輸入平行磁力線之電流，與輸入基於電離層底層導電率所推算之垂直磁力線電場擾動，發現考慮平行磁力線分量電流所造成的TEC與(Vexb)p擾動小於考慮垂直磁力線電場擾動的模擬，此乃因為電離層電場估算必須考慮沿磁場之島電率總和。

In this study, three-dimensional ionosphere electrodynamic model, NRL-SAMI3, is utilized to simulate the ionospheric perturbation due to external direct currents.
We formulate a coupling model for a external current‐ionosphere system considering field-aligned or perpendicular disturbance currents that may be propagated upward from lithosphere during seismics. The lithosphere driven current, ranging around 120±20oE, 30±20oN, and 85km altitude, are included in the electrodynamics solver of NRL SAMI3. Our simulation results indicate that the external current produces the total electron content perturbation (∆TEC) as much as -2.6TECu. The negative ∆TEC response is mainly shown in the southwest of external current; while the positive ∆TEC appear in the southeast of external current. The ion/plasma drift velocity modified due to the external currents affect the equatorial plasma fountain effect and electron densities.
Further analyses suggest that current along magnetic field line (in q direction) plays a relatively more important role in production of electron density and TEC variations in comparison with those in perpendicular directions (in meridional and zonal directions). The magnitude of elecric field perturbation and its polarity (eastward or westward) are related with the distribution of lithosphere driven current along magnetic field line at 85km alitude and the field-aligned integrated Pedersen conductivity. The electric field perturbation may be overestimated if one uses ionospheric conductivities at lower boundary of 85 km altitude instead of field-aligned integrated conductivities. The simulations of coupling the field-aligned current take into account the integrated conductivities, and results in smaller E×B drift and TEC perturbations.

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