摘要： A comprehensive investigation of spread F irregularities over the Indian sector has been carried out using VHF radar and ionosonde observations. Two different categories of spread F observations, one where the onset of the range spread F (RSF) was concurrent with the peak h ′ F (category 1) and another where the RSF onset happened ~90 min after the peak h ′ F time (category 2), are presented. RSF in category 2 was preceded by the presence of oblique echoes in ionograms, indicating the irregularity genesis westward of Sriharikota. The average peak h ′ F in category 1 was ~30 km higher than that in category 2 indicating the presence of standing large‐scale wave structure (LSWS). Occurrence of the blanketing E s during 19:30 to 20:30 Indian Standard Time in category 1 (category 2) was 0% (>50%). Model computation is also carried out to further substantiate the observational results. Model computation indicates that zonal variation of low‐latitude E s can generate zonal modulation in the F layer height rise. It is found that the modulation of the F layer height, linked with the low‐latitude E s , assists the equatorial spread F onset by modifying both the growth rate of the collisional Rayleigh‐Taylor (R‐T) instability and also its efficiency. A predominant presence of low‐latitude E s has been observed, but the increase in the F layer height and the R‐T instability growth in the evening hours will maximize with complete absence of low‐latitude E s . A new mechanism for the generation of LSWS and its implications on R‐T instability is discussed. Significant difference in the low‐latitude E s characteristics has been observed in the concurrent and drifted ESF events Model computation indicates that the E s in the low latitudes can generate LSWS LSWS linked with low‐latitude E s alters the collisional R‐T instability growth rate as well as its efficiency 出版日期： 2016-07 出處： Journal of geophysical research : Space physics (2013 - Present), 2016-07, Vol.121 (7), p.6986-7000 資源來源： Wiley Online Library Journals 識別號： ISSN: 2169-9380 識別號： EISSN: 2169-9402 識別號： DOI: 10.1002/2016JA022659
