文章基本信息

标题：Daytime Equatorial Spread F-Like Irregularities Detected by HF Doppler Receiver and Digisonde
本地全文：下载
作者：B. Olugbon ; E. O. Oyeyemi ; A. Kascheyev 等
期刊名称：Space Weather
印刷版ISSN：1542-7390
出版年度：2021
卷号：19
期号：4
页码：1-15
DOI：10.1029/2020SW002676
语种：English
出版社：American Geophysical Union
摘要：Daytime equatorial spread F (ESF) is not as common as nighttime ESF due to the presence of a highly conducting E-layer during the daytime which counteracts the development of F-layer plasma irregularities. This study presents two rare daytime ESF-like events which occurred over an interval ∼2 h and were detected by the HF Doppler receiver located in Lagos (LAG: geographic: 3.27°E, 6.48°N; dip latitude −1.72°) and the Lowell Digisonde at Ilorin (ILR; 4.68°E, 8.50°N; dip latitude −1.25°), managed by Lowell GIRO Data Center (LGDC). Analysis of the first event revealed ∼30 min periodic oscillations in iso-heights of ionospheric electron density. Shorter period (∼15 min) oscillations appeared simultaneously in HF Doppler measurements and these oscillations lasted nearly 3 h. Close inspection of the ionograms from ILR during this interval (1500–1800 UT) showed the occurrence of small-scale spreading in the F-layer trace which varied in altitude as the disturbance progressed. Computation of the linear growth rate of the collisional Rayleigh-Taylor instability showed that the plasma instability was seeded by a traveling ionospheric disturbance (TID). The characteristics of the second event suggest that horizontal stratifications in plasma density distribution at the reflecting ionospheric layer were responsible for the spread F traces in the ionograms. Analysis of GPS TEC data from Nigeria during these events revealed the presence of wave structures consistent with TIDs.