Event Analysis of the Influence of Strong Tropospheric Convection in Summer on Low-latitude Ionospheric Irregularities in East Asia
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摘要: 利用海南台站和东南亚地区的多种地基和天基观测手段，对2014年7月28日夜间观测到的东亚低纬F区不规则体事件的时空变化及其物理过程进行分析。结果表明，海南台站观测到了罕见的长时间持续的F区电离层不规则体，不同手段观测到的电离层不规则体存在明显的形态差异。不同台站观测到的电离层不规则体活动存在明显的差异。海南台站经度区南北异常峰附近的TEC起伏活动在日落后至午夜附近明显增强，在午夜后明显减弱。C/NOFS卫星轨迹午夜后逐渐接近于磁赤道，且处于较低高度上，几乎总会观测到弱等离子体扰动/泡的发生，与该区域地基观测的弱电离层不规则体活动存在明显的联系。SWARM卫星在黎明海南台站附近经度区仍观测到较强的赤道异常双峰结构，且西侧异常峰区附近仍存在明显的等离子体密度耗空/泡结构。海南台站西侧磁赤道区附近（中南半岛）强对流活动（MCC）激发的重力波种子扰动对东亚低纬区等离子体泡及准周期结构的产生发挥了重要作用。Abstract: Using various ground-based and space-based observation methods from the Hainan station and Southeast Asia, the spatiotemporal changes and physical processes of the irregularity events in the low-latitude F region of East Asia observed on the night of July 28, 2014 were analyzed. The main results are as follows. The Hainan station observed a rare occurrence of long-lasting ionospheric irregularities in the F region, and the ionospheric irregularities observed by different means have obvious morphological differences. There are obvious differences in the activities of ionospheric irregularities observed by different stations. The TEC fluctuation activities near the north-south anomalous peaks in the longitude area of Hainan increased significantly before midnight and weakened significantly after midnight. After midnight, the trajectory of the C/NOFS satellite gradually approached magnetic equator and was at a lower altitude. The occurrence of weak plasma disturbances/bubbles was almost always observed, which is obviously related to the activities of weak ionospheric irregularities observed on the ground in this region. The SWARM satellites still observed the strong two peaks of equatorial anomaly near dawn in the longitude region near Hainan station, and there were still the plasma density depletion/bubble structures near the anomalous peak area on the west side. The seed disturbance (gravity waves) excited by the MCC near the magnetic equator on the west side of the Hainan station (Indochina Peninsula) may play an important role in the generation of plasma bubbles and their quasi periodic structures in the low latitude region of East Asia.
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图 1 海南和东南亚台站的位置及观测范围 （7 条斜线为海南 VHF 雷达的观测方向和范围。圆圈为 GPS 电离层闪烁/TEC 监测仪的观测范围。斜横线为C/NOFS 卫星轨迹，竖线为 SWARM 卫星轨迹）
Figure 1. Location and observation range of Hainan and Southeast Asia stations. (The seven oblique lines are the observation direction and range of Hainan VHF radar. The circles are the observation area of GPS ionospheric scintillation/TEC monitors. The oblique horizontal lines are the trajectories of C/NOFS satellites, and the vertical lines are the trajectories of SWARM satellites)
图 2 海南 VHF 相干散射雷达在不同观测方位观测到的电离层不规则体回波高度–时间–强度（ATI）及雷达波束的仰角和方位角
Figure 2. Altitude-Time-Intensity (ATI) maps of ionospheric irregularity echoes observed by Hainan VHF coherent scatter radar in different observation directions, as well as the elevation and azimuth of the radar beam
图 3 海南 GPS 电离层闪烁监测仪观测到的电离层幅度闪烁指数S4随时间的变化 （不同曲线为接收到的不同卫星信号）
Figure 3. Variation of ionospheric amplitude scintillation index S4 observed by Hainan GPS ionospheric scintillation monitor with time (Different curves are different satellite signals received)
图 4 海南数字测高仪 DPS4 观测到的等离子体漂移速度、 底部F 层最小虚高h'F以及扩展 F 的变化
Figure 4. Variation of the plasma drift velocity, the minimum virtual height of bottomside F layer (h'F) and spread F observed by Hainan digisonde DPS4
图 5 当天夜间东南亚 8 个 GPS 站 TEC 起伏的变化及每个站点的纬度和经度（不同曲线为接收到的不同卫星信号）
Figure 5. Variation of TEC fluctuations of eight GPS sites in Southeast Asia that night, and the latitude and longitude of each site (Different curves are different satellite signals received)
图 6 C/NOFS 卫星当天夜间穿磁赤道区时所探测的离子参数（离子温度、速度和密度）和卫星轨道参数（纬度和高度）的变化
Figure 6. Variation of ion parameters (temperature, velocity and density) and satellite orbit parameters (latitude and altitude) detected by C/NOFS satellite when it crosses the magnetic equatorial region at night
图 7 SWARM 星座在黎明附近穿越海南台站两侧的磁赤道区时探测到的等离子体密度/泡结构变化
Figure 7. Changes in plasma density / bubble structure detected by SWARM constellation when it crosses the magnetic equatorial region on both sides of Hainan station near dawn
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