利用北斗GEO卫星观测数据分析中低纬地区小尺度VTEC时变率

Analysis of small-scale rate of change of VTEC in middle and low latitude regions using GEO satellite observations

利用北斗GEO卫星的静地特性,研究了中低纬地区小尺度垂直总电子含量(VTEC)时变率.给出了利用GEO卫星双频载波相位观测数据计算VTEC时变率(RVTEC)的公式,引入VTEC时变率指数(RVTECI)作为反映电离层活动程度的指标.通过对不同卫星观测结果的比较,确定30°为合适的RVTEC观测截止仰角.对处于南北纬30°之间5个测站共12天的观测数据进行了计算,结果表明:中纬地区VTEC变化最为平缓,RVTECI一般不超过0.01 TECu/s;赤道附近地区某些夜间时段电离层变化较为剧烈,RVTECI可达0.5 TECu/s,1 min内VTEC的变化量可达8 TECu.

Small-scale rate of change of Vertical Total Electron Content（ VTEC） in middle and low latitude regions is analyzed utilizing the geostationary feature of GEO satellites. The equation of calculating rate of change of VTEC（ RVTEC） is presented using GEO dual-frequency carrier-phase observations,and RVTEC index（ RVTECI） is introduced as the index of the grade of ionospheric activity. Through the comparison of computing results from different satellites,30° is chosen to be appropriate cut-off elevation angle to compute RVTEC. Computations are done using 12 days＇ observation data of 5 sites between 30° N and 30° S,the results show that VTEC varies most slowly in middle latitude region meanwhile RVTECI is smaller than 0. 01 TECu/s,ionosphere varies turbulently near the equator during some periods at night,RVTECI reaches 0. 5 TECu/s and variation of VTEC reaches 8 TECu in 1 min in maximum.