Deformation of the ionosphere structure during the space weather events on October–November 2003

We present the spatial maps of the ionosphere–plasmasphere slab thickness τ (ratio of the vertical total electron content, TEC, to the F-region peak electron density, NmF2) during the intense ionospheric storms of October–November 2003. The model-assisted technology for estimate of the upper boundary of the ionosphere, hup, from the slab thickness components in the bottomside and topside ionosphere – eliminating the plasmasphere contribution of τ – is applied at latitudes 35° to 70°N and longitudes −10° to 40°E, from the data of 20 observatories of GPS-TEC and ionosonde networks, for selected days and hours of October and November 2003. The daily–hourly values of NmF2, hmF2 and TECgps are used as the constrained parameters for the International Reference Ionosphere extended to the plasmasphere, IRI-Plas, during the ionospheric quiet days, positive and negative storm phases for estimate of τ and hup. Good correlation has been found between the slab thickness and the upper boundary of the ionosphere for the intense ionospheric storms at October–November 2003. During the negative phase of the ionospheric storm, when the ionospheric plasma density is exhausted, the nighttime upper boundary of the ionosphere is greatly uplifted towards the magnetosphere tail, while the daytime upper boundary of the ionosphere is reduced below 500 km over the Earth.     

基于空间变异特性的格网电离层延迟估计方法

广域增强系统采用格网模型校正用户电离层延迟误差,为保证理想的校正效果,必须精确估计格网点电离层延迟。电离层延迟的空间相关性是完成这一估计的理论依据。针对传统反距离加权法因不能准确描述这种空间相关性而使得估计效果受限的问题,依据空间统计学原理建立了电离层延迟空间变异函数模型,提出一种新的权值计算方法,并通过实际观测数据进行了仿真验证。结果表明,相比于传统方法,这一方法能明显改善格网点电离层延迟估计效果,尤其在穿透点观测数据稀疏的区域,其改善效果更为明显。     

Effects of TADs on the F region of the mid-latitude ionosphere during an intense geomagnetic storm

Based on observations of two ionosondes at Wuhan and Kokubunji, this paper presents effects of TADs on the daytime mid-latitude ionosphere during the intense geomagnetic storm on March 31, 2001. During a positive ionospheric storm, the start of the enhancement of the foF2 (F2 peak plasma frequency) at Wuhan lags that at Kokubunji by 15 min, which corresponds to the time interval of traveling atmospheric disturbances (TADs’) propagation from Kokubunji to Wuhan. Associated with the uplifting of the hmF2 (height of F2 peak) caused by TADs, it is observed by the two ionosondes that the F1 cusp becomes better developed. Therefore, during a geomagnetic storm, TADs originating from the auroral oval may have a strong influence on the shape of the electron density profile in the F1 region ionosphere at middle latitudes. It is highly likely that TADs are responsible for the evolution of the F1 cusp.     

中纬地区日间类扩展F不规则结构的观测研究

基于高频多普勒观测,研究中纬地区日间类扩展F现象及其与其他电离层扰动现象的关联.结果表明：日间类扩展F具有出现时间覆盖面广、持续时间长、与其他电离层扰动相互伴随等特征;形态特征表现为回波弥散（与夜间扩展F相似）,弥散回波的频移多倾向于正向偏移,有时与行进电离层扰动（TIDs）相互伴随.日间类扩展F现象虽然是偶发事件,且发生率极低,但其出现时间及区域的广泛性充分体现了该现象对空间天气及空间环境的影响具有不可忽视的重要性.     

Doppler characteristics of HF spread Doppler clutter recorded at Alice Springs,Australia

Mean night-time peak power, Doppler shift and Doppler width of spread Doppler clutter (SDC) received by a high frequency backscatter radar located at Alice Springs, Australia from 2000 to 2018 is presented as a function of azimuth, sunspot number, time of year and frequency. The sampled region covers 90 degrees from West to North and includes the northern and southern equatorial anomalies.SDC peak power diminished across all azimuths during the winter solstice from around May to August (local winter) coinciding with the global decrease in F layer density due to the annual non-seasonal F2 anomaly but was generally constant during the equinoxes. In contrast, SDC Doppler width and inbound Doppler shift both increased during the equinoxes and exhibited azimuthal dependence related to the eastward equatorial plasma drift.SDC peak power increased with increasing sunspot number with frequency dependence during winter but not summer. Inbound Doppler shift and Doppler width increased with increasing sunspot number during equinox but not solstice with a strong dependence on azimuth and a weak dependence on frequency.