https://repository.kopri.re.kr/handle/201206/5117 Tue, 07 Apr 2026 05:38:59 GMT 2026-04-07T05:38:59Z https://repository.kopri.re.kr/handle/201206/6351 Title: The source of the steep plasma density gradient in middle latitudes during the 11-12 April 2001 storm Authors: Jee, Geonhwa; Kim, Khan-Hyuk; Hyosub Kil; J. Goldstein; Park, S.; Lee, Dong-Hun Abstract: A steep plasma density gradient has been observed in the middle-latitude F region during large geomagnetic storms. This phenomenon can be understood as a special form of the middle-latitude ionization trough (hereafter trough), but its causal linkage has not yet been clarified. We investigate the association of the steep density gradient and the trough by comparing their morphologies and occurrence locations using the satellite and round observation data during the 11-12 April 2001 storm. Steep density gradients are detected in the dusk sector at the equatorward edges of the aurora by the Defense Meteorological Satellite Program (DMSP) F13 spacecraft. The locations of the steep density gradients coincide with the locations of the ionospheric footprints of the plasmapause identified by the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) satellite. These observations demonstrate that the steep density gradient is created at the typ-ical location of the trough. However, the steep density gradient is not produced by the formation of an intense trough during the storm. The temporal evolution of the total electron content maps shows that the steep density gradient observed at dusk by DMSP is associated with the plasma density enhancement in the dayside and its corotation into the dusk sector. The severe plasma density enhancement in middle latitudes, in combination with the troucausal linkage has not yet been clarified. We investigate the association of the steep density gradient and the trough by comparing their morphologies and occurrence locations using the satellite and round observation data during the 11-12 April 2001 storm. Steep density gradients are detected in the dusk sector at the equatorward edges of the aurora by the Defense Meteorological Satellite Program (DMSP) F13 spacecraft. The locations of the steep density gradients coincide with the locations of the ionospheric footprints of the plasmapause Sun, 01 Jan 2012 00:00:00 GMT https://repository.kopri.re.kr/handle/201206/6351 2012-01-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/8524 Title: Seasonal and height variation of gravity wave activities observed by a meteor radar at King Sejong Station (62°S, 57°W), Antarctica Authors: Kim, Jeong-Han; Choi, Jongmin; Lee, Changsup; Kim, Yong Ha; Jee, Geonhwa Abstract: We have analyzed wind data from individual meteor echoes detected by a meteor radar at King Sejong Station, Antarctica to measure gravity wave activity in the mesopause region. Wind data in the meteor altitudes has been obtained routinely by the meteor radar since its installation in March 2007. The mean variances in the wind data that were filtered for large scale motions (mean winds and tides) can be regarded as the gravity wave activity. Monthly mean gravity wave activities show strong seasonal and height dependences in the altitude range of 80 to 100 km. The gravity wave activities except summer monotonically increase with altitude, which is expected since decreasing atmospheric densities cause wave amplitudes to increase. During summer (Dec. - Feb.) the height profiles of gravity wave activities show a minimum near 90 - 95 km, which may be due to different zonal wind and strong wind shear near 80 - 95 km. Our gravity wave activities are generally stronger than those of the Rothera station, implying sensitive dependency on location. The difference may be related to gravity wave sources in the lower atmosphere near Antarctic vortex. Fri, 01 Jan 2010 00:00:00 GMT https://repository.kopri.re.kr/handle/201206/8524 2010-01-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/8525 Title: Mesospheric temperatures estimated from the meteor decay times over King Sejong Station(62.2°S, 58.8°W), Antarctica Authors: Jee, Geonhwa; Kim, Yong Ha; Kim, Jeong-Han Abstract: A VHF meteor radar has ben operated at King Sejong Station (62.2°S, 58.8°W), Antarctica since March 2007 for the observations of the neutral winds in the mesosphere and lower thermosphere region. In addition, the radar observation allows usto estimate the neutral temperature from the measured meteor decay times of the meteor echoes by utilizing Hockings method (Hocking, 1999). For this temperature estimation, the meteor echoes observed from March 2007 to July 2009 were divded, for the first time, into weak and strong echoes depending on the strength of estimated relative electron line densities. The estimated temperatures are then compared the temperature measurements from the spectral airglow temperature imager (SATI) which has also been operated at the same location since 2002. The estimated temperatures from strong echoes were significantly lower than the temperatures estimated from weak echoes by on average about 31 K. As was done in most previous studies, we also derived the temperature by using all echoes without dividing into weak and strong, which produces about 10 K lower than the weak echoes. Among these hree estimated temperatures, the one from weak echoes was most similar to the SATI temperature. This result indicates that the strong echoes tend to reduce the estimated temperature and therefore need to be removed in the estimation procedure. We will also present the comparison of the estimated temperature with other measurements, for example, from the TIMED/SABER instrument and the NRLMSISE- 00 empirical model results as a further validation. Fri, 01 Jan 2010 00:00:00 GMT https://repository.kopri.re.kr/handle/201206/8525 2010-01-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/8018 Title: The Seasonal Variation of Mesospheric Temperature Estimated from VHF Meteor Radar at King Sejong Station (62.2, 58.8), Antarctica Authors: Kim, Jeong-Han; Jee, Geonhwa; Lee, Changsup; Kim, Yong Ha Abstract: A VHF meteor radar and SATI instruments have been operated at King Sejong Station (62.2？; , 58.8？; ), Antarctica, to study the mesospheric characteristics in southern high latitude region since March 2007 and February 2002, respectively. Using data from two instruments, we estimated the mesospheric temperatures according to the Hocking (1999)？; method, which requires the slope of logarithmic inverse decay times vs. height and the temperature gradient at meteor peak altitude, during March 2007 through July 2009 and compared the results with the SATI temperatures. The temperatures derived from observed decay times seem to be consistent with the rotational temperatures of SATI OH(6-2) and O2(0-1) emission during March through October. The annual variation of estimated temperatures, which clearly shows a minimum during southern summer, is a good agreement with observations at other stations. The mean estimated temperature during summer which is much colder than that of CIRA86 model, as much as by 30 K, is comparable with the results of L？; bken et al. (1999) which reported the mean mesopause temperature of 120 to 140 K from in-situ measurements using falling spheres performed at Rothera Station (68？; , 68？; ). In addition, from the results of meridional wind analysis, it was found that the equator-ward meridional winds are dominant flows during southern summer. In this study, we discuss the seasonal variations of mesospheric temperatures estimated from meteor decay times and the relation between the estimated temperatures and meridional wind measured from same instrument. Fri, 01 Jan 2010 00:00:00 GMT https://repository.kopri.re.kr/handle/201206/8018 2010-01-01T00:00:00Z