Abstract
We report, for the first time, the afternoon (i.e., from noon to sunset time)
observations of the northern mid-latitude E-region field-aligned irregularities (FAIs)
made by the very high frequency (VHF) coherent backscatter radar operated continuously
since 29 December 2009 at Daejeon (36.18°N, 127.14°E, 26.7°N dip latitude) in South
Korea. We present the statistical characteristics of the mid-latitude afternoon E-region
FAIs based on the continuous radar observations. Echo signal-to-noise ratio (SNR) of the
afternoon E-region FAIs is found to be as high as 35 dB, mostly occurring around 100–135
km altitudes. Most spectral widths of the afternoon echoes are close to zero, indicating
that the irregularities during the afternoon time are not related to turbulent plasma
motions. The occurrence of afternoon E-regional FAI is observed with significant
seasonal variation, with a maximum in summer and a minimum in winter. Furthermore, to
investigate the afternoon E-region FAIs- Sporadic E (Es) relationship, the FAIs have
also been compared with Es parameters based on observations made from an ionosonde
located at Icheon (37.14°N, 127.54°E, 27.7°N dip latitude), which is 100 km north of
Daejeon. The virtual height of Es (h’Es) is mainly in the height range of 105 km to 110
km, which is 5 km to 10 km greater than the bottom of the FAI. There is no relationship
between the FAI SNR and the highest frequencies (ftEs) (or blanket frequencies (fbEs)).
SNR of FAIs, however, is found to be related well with (ftEs–fbEs).
Publisher
The Korean Space Science Society
Subject
General Earth and Planetary Sciences,General Physics and Astronomy
Cited by
3 articles.
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