2009年1月平流层爆发性增温期间全球电离层响应的研究

2009年1月平流层爆发性增温(Stratospheric Sudden Warming, SSW)事件是有记录以来最强、持续时间最长的一次主增温事件(Major Warming Event, MWE), 期间太阳活动和地磁活动均处于较低的水平, 因此非常有利于研究电离层对平流层增温事件的响应情况. 本文利用COSMIC (Constellation Observing System for Meteorology, Ionosphere, and Climate)系统提供的掩星数据, 使用Kriging方法分别构建了此次SSW期间及平静期的电离层N_mF₂, h_mF₂和110～750km高度范围的垂直积分TEC (简称VTEC)地图, 同时从全球定位导航卫星系统服务组织(International GNSS Service, IGS)发布的全球电离层TEC地图(Global Ionospheric Maps, GIMs)中提取了日固坐标系(Sun-fixed, 地磁纬度和地方时)下全球TEC地图. 通过对比发现, SSW期间与平静期相比, 地磁纬度中低纬电离层参数存在早晨上升, 下午和夜间下降的现象. 利用OSTM/JASON-2卫星高度计观测值进行验证后的结果显示, 此前研究均未有提及的夜间时段电离层参数N_mF₂, h_mF₂和TEC (VTEC和IGS TEC)的下降现象的确存在.

Observations of the Global Ionospheric Response During the January 2009 Stratospheric Sudden Warming Event

A major Stratospheric Sudden Warming (SSW) in January 2009 was the strongest and most prolonged on record. In the period of this warming event, the solar activity and geomagnetic disturbance are extremely low. Hence it provides a good opportunity to investigate the response of the ionosphere to SSW event. The Kriging method is adopted to construct map of N_mF₂, h_mF₂, and integrated Vertical TEC (VTEC) within height ranging from 110km to 750km with data derived form COSMIC radio occultation system. And global TEC maps in the Sun-fixed coordinate are also withdrawn from IGS GIMs. By comparing these maps, it can be found that N_mF₂, h_mF₂ and TEC increase in the morning hours and decrease in the afternoon and night. Under fixed location and local time bins, cases during SSW and non-SSW days from global COSMIC observations are compared, which shows that N_mF₂, h_mF₂, and VTEC during SSW days, on average, increase 17%, 12%, 10km in the morning , decrease 10%, 15%, 16km in the afternoon, and decrease 19%, 23%, 11km in the afternoon respectively. According to the results of comparison of IGS GIMs during SSW and no SSW days, the main difference occurs in the middle and low latitude region, moves along with UT time and corresponds to the position of ionospheric anomaly. It also can be found that increase of TEC (VTEC and IGS TEC) is stronger in the northern hemisphere than in the southern hemisphere during the morning time. Furthermore, the phenomenon that N_mF₂, h_mF₂ and TEC (VTEC and IGS TEC) are decreased in the night hours has never been mentioned by previous studies. So altimeter observations by the OSTM/JASON-2 satellite are used for further verification and the phenomenon is validated at last.