大耀斑期间向日面电离层总电子含量的响应个例分析

利用2001年4月15日1336UT耀斑爆发期间向日面GPS观测数据提取的总电子含量的时间变化曲线。分析了向日面电离层对这次耀斑的响应特点．结果表明，耀斑期间向日面电离层出现了总电子含量突增事件．最大总电子含量增加量约为2．6TECU，在0600LT和1800LT都观测到了总电子含量突增，世增加幅度仅为0．5-1TECU．在高纬地区，由于电离层闪烁，从TEC时间变化曲线提取不出来总电子含量增加值．从各卫星星下点处的TEC增加量和各星下点处的太阳天顶角的关系可以看到，TEC增加量与太阳天顶角有关，太阳天顶角越大，TEC增幅越小。另外，从总电子含量时间变化率曲线上还观测到了时间同步的小尺度扰动，通过与耀斑期间硬X射线辐射通量的比较，发现两者有明显的相关性，电离层中的这种扰动与耀斑期间的硬X射线或远紫外辐射有关．

ONE CASE STUDY ABOUT THE IONOSPHERIC RESPONSE TO ONE GREAT SOLAR FLARE IN THE SUN-LIT HEMISPHERE

The characteristics of the ionospheric response to one great solar flare was studied using the total electron content derived from GPS observational stations in the whole sun-lit hemisphere under International GPS Service for Geodynamics (IGS). It was found that the largest enhancement of the Sudden Increase of Total Electron Content (SITEC) during this flare is about 2.6 TECU (1 TECU= 1016/m2). The effects of solar flare radiation on the ionosphere can be recognized even in the region at 0600 LT or 1800 LT. Due to the ionospheric scintillation, the TEC enhancement couldn't be derived from temporal TEC variation curves in the high latitudes. On the other hand, the synoptic picture of the sun-lit ionospheric response to the flare was obtained and the results showed the relationship of TEC enhancements with solar zenith angles. The larger the solar zenith angle, the smaller the TEC enhancement. It was worth mentioning that even the minor fast changes in TEC during this flare can be revealed from the changing rate of the temporal TEC variation curves in mid- and low latitudes. These minor and global synchronous disturbances of TEC were compared with the solar X-ray flux of this flare observed by satellites, and a close correlation between those minor ionospheric disturbances and the hard X-ray flux fluctuations is found.