赤道电离异常特征参量地方时梯度的日变化特征——Swarm卫星观测

Swarm A/C卫星在460 km左右高度伴飞,地方时差异5.6 min,为赤道电离异常(Equatorial Ionization Anomaly,EIA)研究提供了一个绝好的观测机会.本文利用Swarm A/C卫星2014—2017年期间的电子密度观测数据,研究了地磁活动相对平静期EIA特征参量地方时梯度的日变化特征.分析发现:(1)EIA驼峰强度和位置的地方时梯度,ΔNe和Δβ,在正午前随地方时线性减小,午后达到极小值;傍晚前后,二者先增大后减小.该日变化特征在各季节具有普适性.(2)ΔNe和Δβ的日变化表现出紧密的相关性,且在白天和日落后两个时段内遵从明显不同的线性关系.(3)ΔNe和Δβ对赤道等离子体抬升通量地方时梯度,Δflux,的响应非常迅速,滞后时间约为1 h.

Diurnal variations of local time gradient of EIA characteristic parameters observed by Swarm satellites

Swarm A/C satellites are flying side-by-side at altitude of about 460 km, with a local time separation of 5.6 min. It provides an unique observational opportunity for studies about Equatorial Ionization Anomaly (EIA). With help of electron density recorded by the Langmuir Probe (LP) on-board Swarm A/C during 2014-2017, diurnal variations of local time gradient of EIA characteristic parameters undering the relative quiet period of geomagentic activity are investigated in this paper. Some novel and interesting results are presented as follows:(1) Local time gradient of EIA crest intensity and location, ΔNe and Δβ, linearly decrease with local time during the morning and the minimal appear during post-noon; a plus enhancement take place at dusk. The aforementioned diurnal variations exhibit less dependent on season. (2) Diurnal variations of ΔNe and Δβ suggest a close linkage with each other, exhibiting remarkable different linear relations during daytime and post-sunset, respectively. (3) Variations of ΔNe and Δβ exhibit quick response to the local time gradient of up-driving flux, Δflux, with a lagging time of around 1 hour.