基于三亚VHF雷达的场向不规则体观测研究:1.电离层E区连续性回波

基于三亚(109.6°E,18.4°N)VHF电离层相干散射雷达观测,分析了我国低纬电离层E区场向不规则结构连续性回波的发生特征.研究结果表明:白天,E区连续性回波的多普勒速度范围为-50至25m/s,多普勒宽度主要分布在20至70m/s;连续性回波的高度大约以1km/h的速度缓慢下降,与偶发E层(Es)底部所在高度(hbEs)有很好的相关性,表明在背景电场影响下,Es经梯度漂移不稳定性产生场向不规则结构,引起E区连续性回波.夜间,E区连续性回波的多普勒速度范围为-50至50m/s,多普勒宽度为20至110m/s,回波在时间-高度-强度图上常呈现多层结构,可能与潮汐引起的多个离子层相关;而E区连续性回波的短暂中断,以及120km以上高E区连续性回波的发生,则可能归因于赤道扩展F极化电场的影响.此外,对E区连续性回波多普勒速度与全天空流星雷达风场观测的比较发现,在100km以下,多普勒速度与子午风场有很好的相关性.

Observations on the field-aligned irregularities using Sanya VHF radar:1.Ionospheric E-region continuous echoes

The occurrence characteristics of continuous radar echoes from low-latitude ionospheric E-region field-aligned irregularities are investigated, using the data from Sanya (109.6°E, 18.4°N) VHF coherent radar. The observational results show that the Doppler velocity and spectral width of daytime continuous echoes range from -50 to 25 m/s, and from 20 to 70 m/s, respectively. The echoes descend slowly with a descent rate of 1 km/h, and are highly correlated with the descending of the bottom height of Es trace (h_bEs). This probably indicates that the background electric field provides a favorable condition for the gradient-drift instability below the density layer producing the continuous echoes. While at nighttime, the Doppler velocity and spectral width of continuous echoes range from -50 to 50 m/s, and from 20 to 110 m/s, respectively. The E-region multiple echo layers, echo layer disruption and upper E-region echo layer generation are often observed during the post-sunset hours, which could be associated with the tidal ion layers, and with the mapping of polarization electric fields generated within the equatorial plasma bubbles, respectively. Additionally, the meridional winds derived from continuous echoes (coherent radar) were generally consistent with those estimated from specular meteor trails (all-sky meteor radar) below 100 km.