中文摘要：

利用国际IGS网和美国CORS网提供的GPS TEC观测资料,构建了北美地区的二维TEC扰动图像,分析研究了2012年7月14日一次强磁暴期间大尺度电离层行进式扰动在北美地区的二维结构以及扰动沿着70°W左右的子午线在南北半球的分布与传播特性.研究结果表明,磁暴急始开始90分钟后,伴随着一次亚暴的膨胀相,在北半球发生了一次大尺度电离层行进式扰动事件.该扰动在北美地区形成幅度1.2-2.2 TECU,宽度达4000 km的等相面,以190°的传播方位角,西南向传播了2000 km,扰动的周期和水平相速度分别为40-60 min,500 m/s.通过台链观测发现,该扰动向西南方向一直传播到约30°N,在传播过程中,扰动的绝对振幅在55°N至42°N之间逐渐增强并达到最大值2.2 TECU,在42°N以南逐渐衰减.通过对相关时间段内北美亚极光带地磁观测数据的分析发现,在65°N至85°N、100°W至150°W之间,地磁场水平分量在LSTID发生前出现明显变化,显示极光电集流增强,这一区域是北美地区观测到的LSTID事件最可能的源区.北半球的电离层扰动消失之后约1小时,通过南半球GPS台链观测到南向电离层扰动,该扰动的绝对振幅为1.8 TECU,相速度为400 m/s左右,传播范围局限在16°S至20°S.在南北半球的低纬赤道区,台链观测没有发现与北美LSTID关联的电离层扰动.根据台链上扰动传播的中断,我们认为,南半球台链观测到的电离层扰动并不是北半球LSTID直接跨赤道传播到南半球的结果,而是北半球电离层扰动在赤道地区的耗散过程中形成的二次扰动引起的。

英文摘要：

We used the total electron content（ TEC） data observed from International GNSS Service（ IGS） and Continuously Operating Reference Stations（ CORS） in the United States,constructed 2D TEC perturbation maps during sudden commencement of the geomagnetic storm on July 14, 2012. Then, we analyzed the structures of the large-scale traveling ionospheric disturbance（ LSTID） on North America and the propagation properties of the LSTID during its propagation across northern and southern hemispheres along the meridian of about 70° W. 90 minutes after the storm sudden commencement（ 20： 30 UT,14： 30 LT）,following a substorm expansion phase,a LSTID event took place over North America. The LSTID propagated southwestward at a distance of longer than 2000 km,with an amplitude of 1. 2 - 2. 2 TECU and a mean azimuth of 190°（ clockwise from north）. The phase fronts of the LSTID extended horizontally to 4000 km. The period and phase velocity of the LSTID are about 40 - 60 minutes and 500 m / s,respectively. The observation of GPS station chain indicates that the disturbance propagated to the latitude of about 30° N. During its propagation, the amplitude enhanced firstly until reaching the maximum（ about 2. 2 TECU） at about 42° N,and then attenuated.According to the propagation characteristics and the disturbances of H component of geomagnetic field,we found the source region of the LSTID seems to be in the range of 65° N - 85° N and 100 ° W -150° W. In the southern hemisphere,we observed a southwardpropagating LSTID through the GPS station chain. This disturbance appeared at 22： 10 UT,about 1 hour after the disappearance of the LSTID in northern hemisphere,with amplitude of 1. 8 TECU and phase velocity of 400 m / s. It was observed at a limited latitudinal range of 16° S - 20° S. Due to the discontinuity of the propagation,we believe that the LSTID in the southern hemisphere disturbance may be a secondary wave possibly excited by the dissipation of the LSTID observed in the northern hemisphe