基于掩星观测的全球低纬地区电离层不均匀体形态分析

Global morphology of ionospheric irregularities in the low latitudes using radio occultation technique

基于气象、电离层和气候星座观测系统(Constellation ObservingSystem for Meteorology,Ionosphere and Climate,COSMIC)掩星闪烁指数观测数据,将遮掩点的位置作为电离层不均匀体出现的位置,对比分析了电离层E区不均匀体和F区不均匀体随时间、空间、太阳活动和地磁活动的变化.发现E区闪烁主要出现于夏季半球的中纬地区;而F区闪烁主要出现于春秋季的磁赤道和低纬地区,受到地磁场的强烈控制.除季节因素外,太阳活动对E区闪烁的影响并不是基本的,而赤道异常和赤道附近的F区闪烁受到太阳活动的显著控制:相比太阳活动低年,高年的F区闪烁强度更大,且扩展至更高的纬度.地磁扰动时,中低纬地区电离层E区闪烁的全球分布与地磁平静时相似,但是闪烁的强度总体上略有增加,尤其是凌晨时段(00:00—06:00LT);中低纬地区电离层F区闪烁的全球分布也与地磁平静时相似,但是闪烁强度明显增加,且扩展至更高的纬度,尤其是00:00—06:00LT及18:00—24:00LT的太平洋扇区.两者对比表明,电离层F区闪烁对地磁活动更为敏感.将COSMIC掩星与天基原位观测的闪烁出现率结果进行对比,发现掩星手段不仅可以反映全球尺度的电离层不均匀体变化特征,包括它随季节/经度、地方时、太阳活动和地磁纬度的变化,而且可以反映电离层不均匀体随高度的变化,这是以往的观测手段难以拥有的.

Based on the amplitude scintillation index S4 observed from Constellation Observing System for Meteorology,Ionosphere and Climate(COSMIC)radio occultation technique,the radio occultation point is taken as the position of the ionospheric irregularities resulting in the ionospheric scintillation phenomena.In this paper,the temporal and special variations,as well as its dependence on solar activities and geomagnetic activities of the ionospheric Eregion irregularities and F-region irregularities are analyzed.It is found that the E region irregularities mainly occur in the mid-latitude of the summer hemisphere,the F region irregularities mainly occur in the equatorial and low latitudes during spring and autumn,which are strongly controlled by the geomagnetic field.In addition to the seasonal influence,the dependence of E region irregularities on the solar activity is not fundamental,while the solar activity has a distinct impact on the F-region irregularities in the equatorial ionization anomaly and equatorial region.In comparison with those during the low solar activity years,the intensity and latitudinal range of F region irregularities are much greater and wider during the high solar activity years.In general,the morphology of E-region irregularities during the geomagnetic active periods is similar to that during the geomagnetic quiet period.However,the intensity of E region scintillation increases slightly,especially during 00:00-06:00LT.Meanwhile,the morphology of F-region irregularities during the geomagnetic active periods is also similar to that during the geomagnetic quiet period.The intensity of F region scintillation increases notably and the latitudinal range extends to be wider,especially during 00:00-06:00LT and 18:00-24:00LT in the Pacific sector.In comparison with the scintillation occurrence results from space-based insitu observations,it is found that GNSS occultation technique can not only reflect the detailed characteristics of ionospheric irregularities on a global scale,such as seasonal/longitudinal variations,and its dependence on local time,solar activities and geomagnetic latitudes,but also reflect the variation of ionospheric irregularities with altitude,which is unprecedented for the previous observational techniques.