Investigation on the Occurrence of Mid-Latitude E-Region Irregularity by Wuhan VHF Radar and Its Relationship With Sporadic E layer

Abstract

By using the 2015–2016 data set of newly built Wuhan very high-frequency (VHF) radar, we investigate the occurrence of E-region field-aligned irregularities (FAIs) in mid-latitude China region for the first time. Wuhan E-region FAIs present the strongest occurrence of quasi-periodic (QP) echoes at postsunset period in the height range of 100–120 km and moderate occurrence of continuous echoes at postsunrise period in the height range of 90–100 km. Characteristics including temporal and altitudinal distribution, Doppler spectra and period of QP echoes are presented from a statistical point of view. We find that E-region FAIs observed by Wuhan VHF radar show strong linkage with the concurrent sporadic E layer observed by ionosonde. In general, Doppler spectra present type 2 feature with velocity in the range of ±50 m/s and width less than 50 m/s. Our results also indicate that mid-latitude E-region FAIs are closely associated with Es layer. Several mechanisms were proposed to interpret the mid-latitude E-region FAIs; however, further investigation is required to understand the generation with different ionospheric background and irregularity types.