Statistical characteristics and occurrences of the F-region field-aligned irregularities in middle latitudes observed with Korea VHF coherent scattering radar

We report for the first time of the long term characteristics and percentage occurrences of F-region field-aligned irregularities (FAIs) in the middle latitude observed with Korea VHF coherent scattering radar. This radar was built at Daejeon(36.18°N, 127.14°E, dip latitude 26.7°N) with 40.8 MHz operating frequency for continuous monitoring of the behavior of electron density irregularities in the middle latitude. From more than three-year of continuous observations since 2010, we have obtained the diurnal and seasonal characteristics of a signal-to-noise ratio and percentage occurrence variations from F-region FAIs over Korea peninsular. F-region FAIs appeared frequently at right after the sunset in both equinoxes, but pre- and post-midnight in summer season. F-region irregularities are intensified after sunset to before sunrise, and then the occurrence of F-region FAIs is rapidly decreased after sunrise. Peak height of F-region irregularities have seen around 300 km altitudes in the evening, then at higher altitude up to 400 km near local midnight and then lower altitudes around 300 km again in the early morning. And also we found that the obtained F-region echoes can be classified as E-region's continuous and quasi-periodic echoes, even though, the duration, occur time and locations are different from Kwak et al. (this issue).