Abstract:Based on 1999~2009 total electron content (TEC) data from IGS, we studied semiannual and seasonal variations of the global TEC in the daytime (Idc) and nighttime (Inc) as well as solar and geomagnetic effects on these variations. The main features are outlined as follows: the maximum values of Idc commonly appear in equinox seasons| in the northern ‘near-pole’ region and south America, the semiannual variation character of Idc is significant. Inc has only semiannual variation at low latitudes, and the semiannual variation of Idc and Inc change with the solar activity. At high solar activity years, in more than 85% area of the globe, the maximum value of Idc appears in equinox seasons. Seasonal variation of Idc and Inc change with latitude and longitude, and seasonal variation is apparent at high solar activity years. The variation of Idc and Inc correlates well with the solar P index, where the correlation coefficient reached 0.9. However, it poorly correlated with geomagnetic Dst, Kp, Ap index, where the correlation coefficient is less than 0.4. We further demonstrate that ionosphere photochemical production rate, which is controlled by solar zenith angle, plays a major role in the overall variation of TEC.
SHI Shuangshuang,HUANG Jinsong,FENG Jiandi et al. Analysis of TEC Variation Characteristics in Daytime and
Nighttime Based on the IGS Data[J]. jgg, 2015, 35(2): 293-297.