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We present preliminary observations of the field-aligned-irregularities (FAIs) in the E and F regions during the solar\udminimum (2009 - 2010) using the 40.8 MHz coherent backscatter radar at Daejeon (36.18°N, 127.14°E, 26.7°N dip latitude)\udin South Korea. The radar, which consists of 24 Yagi antennas, observes the FAIs using a single beam with a peak power of\ud24 kW. The radar has been continuously operated since December 2009. Depending on the manner of occurrence of the\udbackscatter echoes, the E-region echoes are largely divided into two types: quasi-periodic (QP) and continuous echoes.\udOur observations show that the QP echoes occur frequently above an altitude of 105 km in the post-sunset period and\udcontinuous echoes occur preferentially around an altitude of 105 km in the post-sunrise period. QP echoes appear as\udstriated discrete echoes for a period of about 10 - 20 min. The QP-type echoes occur more frequently than the continuoustype\udechoes do and the echo intensity of the QP type is stronger than that of the continuous type. In the F region, the FAIs\udoccur at night at an altitude interval of 250 - 450 km. As time proceeds, the occurrence height of the FAIs gradually increases\uduntil early in the morning and then decreases. The duration of the F-region FAIs is typically a few hours at night, although,\udin rare cases, FAIs persist throughout the night or appear even after sunrise. We discuss the similarities and differences of\udthe FAIs observed by the Daejeon radar in comparison with other radar observations

journal of astronomy and space sciences

Characteristics of the E- and F-region field-aligned irregularities in middle latitudes: Initial results obtained from the Daejeon 40.8 MHz VHF radar in South Korea