利用全球電離層圖之全電子含量探討2022年1月15日東加海底火山 ( -175.39°E, -20.55°N) 爆發所引起電離層全電子含量之二維結構和變化。以觀測天之前後15日資料建構中位數和其四分位數為背景，計算觀測天與背景之差值，藉此，探討火山爆發引起之全電子含量偏移擾動。結果顯示，火山爆發後持續12小時 (0500~1600 UT)，其方圓約1650公里範圍內，電離層全電子含量急劇減約5~10 TECu (TEC unit，1 TECu = 106 #/cc)(50%)。而於爆發後17~23小時 (2100~0300 UT) 全電子含量增強2~18 TECu (50%)。此外，利用福爾摩沙衛星七號電離層掩星觀測之電子濃度廓線，研究此區域內之電離層電子濃度與高度變化，背景資料為前後3日。發現火山爆發後持續12~13小時 (0500~1700 UT)，電離層F2層層峰電子濃度最大減少幅度約8×105 #/cm3 (74%)。相似的，電離層F2層層峰電子濃度也於爆發後17~21小時 (2100~0100 UT) 最大增加幅度約1×106 #/cm3 (84%) 現象。另外，使用福衛七號搭載離子速度儀觀測資料，檢視550公里軌道高度之離子參數變化。結果顯示，爆發後6小時 (0500~1100 UT) 離子濃度最大減少3×105 #/cm3 (95%)，溫度上升2000 K (228%)；爆發後17~23小時 (2100~0300 UT) 離子濃度最大增加6×105#/cm3 (472%)。當日夜間電漿濃度顯著減少成因為火山爆發產生海嘯引起電離層洞之機制、離子速度向下為電離層背景西向電場所引起，次日白天電漿濃度顯著增加為電離層光化學產生率增大所致。;This study investigates the impact of the underwater volcanic eruption near Tonga ( -175.39°E, -20.55°N) on January 15, 2022 by the Total Electron Content (TEC) of Global Ionosphere′s Map (GIM). The background median and quartile values were constructed using data from the 15 days before and after the eruption. By comparing the observation day to this background, TEC perturbations caused by the eruption were analyzed. Findings indicate that within approximately 1650 kilometers of the eruption, the TEC of the ionosphere dropped by 5~10 TEC units (TECu)(50%), for 12 hours post-eruption (0500~1600 UT). Between 17 and 23 hours post-eruption (2100~0300 UT), the TEC increased by 2~18 TECu (50%). Additionally, using electron density profiles from the FORMOSAT-7/COSMIC-2 ionospheric radio occultation observated the variations of verticle electron density. The background data were constructed from the 3 days before and after the eruption. The results revealed that the peak electron density of the F2 layer decreased by 8×105 #/cm3 (74%) for 12~13 hours post-eruption (0500~1700 UT) and increased by 1×106 #/cm3 (84%) between 17 and 21 hours post-eruption (2100~0100 UT). In addition, Ion velocity measurements from FORMOSAT-7/COSMIC-2 at 550 kilometers altitude showed a decrease in ion density by 3×105 #/cm3 (95%) and a temperature increase of 2000 K (228%) for 12 hours after the eruption (0500~1600 UT). Between 17 and 23 hours post-eruption (2100~0300 UT), ion density increased by 6×105 #/cm3 (472%). At nighttime of the eruption day decreasing plasma density is attributed to the formation of an ionospheric hole caused by the tsunami generated by the volcanic eruption. The downward ion velocity is due to the background westward electric field in the ionosphere. The increasing plasma density during the daytime on the next day is caused by an enhanced ionospheric photochemical production rate.
