• Journal of Astronomy and Space Sciences
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• 제33권1호
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• pp.13-19
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• 2016

In recent years, there has been renewed activity in the study of local plasma density enhancements in the low latitude F region ionosphere (low latitude plasma blobs). Satellite, all-sky airglow imager, and radar measurements have identified the characteristics of these blobs, and their coupling to Equatorial Plasma Bubbles (EPBs). New information related to blobs has also been obtained from the Communication/Navigation Outage Forecasting System (C/NOFS) satellite. In this paper, we briefly review experimental, theoretical and modeling studies related to low latitude plasma blobs.

• 우주기술과 응용
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• 제3권3호
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• pp.239-256
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• 2023

지구 전리권은 고층대기의 일부가 이온화되어 전파에 영향을 주는 플라즈마 상태로 존재하는 영역으로 통신과 관련하여 실생활에 직접적으로 영향을 주어 오랜 기간 연구되어온 분야이다. 고도에 따라 전자밀도를 이루는 주된 이온에 따라 D-층, E-층, F-층으로 구분되며, 전자 밀도에 비해 중성대기 밀도가 매우 커서 그 영향을 고려한 플라즈마로 기술되어야 한다. 또한 태양에서 시작되어 지표면에 이르는 영역까지 전리권 외부의 영향이 직접적으로 반영되는 영역으로 복잡하고 다양한 영역의 연구가 연관되는 분야이다. 본 논문에서는 지구 고층대기가 이온화되어 전리권을 형성하는 과정을 설명하고 중·저위도 전리권의 특성에 대해 소개하였다. 또한 현재까지 전리권과 관련하여 국내 연구자들이 참여한 연구를 소개하고 향후 전리권 연구 분야의 교류 활성화에 활용되기를 기대한다.

• 천문학회보
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• 제34권1호
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• pp.78.1-78.1
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• 2009

• Journal of Positioning, Navigation, and Timing
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• 제8권4호
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• pp.225-232
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• 2019

The satellite-based ionospheric model consists of local first-order plane function parameters for individual satellites and provides excellent accuracy in the flat ionospheric environment of the Korean Peninsula. This paper analyzes the performance of such model under the rapid changes in the ionosphere. Rapid changes in the ionosphere were observed in Korea from September to October 2014, and a satellite-based ionosphere model was applied to Wide Area Differential GPS (WADGPS) to analyze the navigation performance and the performance of estimating ionospheric delay errors. After processing the test data, it was confirmed that there was a deterioration in navigation performance and extrapolation performance in low-latitude areas and analyzed the cause.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2003년도 한국우주과학회보 제12권2호
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• pp.81-81
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• 2003

We report the plasma blob events that were observed from KOMPSAT-1 (2250 LT, 685-km altitude) and from DMSP F15 (2130 LT,840-km altitude) in the low-latitude ionosphere. The global distribution of blobs showed a season-longitudinal dependence similar to the distribution of the equatorial plasma bubbles, although they were observed along the ${\pm}$15 dip latitudes. The blobs drifted upward relative to the ambient plasmas, and the electron temperatures and H+ proportions were lower within the blobs compared to those in the background. These characteristics of the plasma blobs are very similar to the characteristics of the equatorial plasma bubbles. Then, we suggest that the blobs were originated from the lower altitudes by the mechanism that drives an upward drift of the plasma bubbles. The blob events did not occur in a correlated way with the magnetic activity or daily variation of the solar activity.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2008년도 한국우주과학회보 제17권2호
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• pp.30.4-31
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• 2008

Formation of longitudinally wave-like plasma density structure in the low-latitude F region is now a well-known phenomenon from the extensive studies in recent years. Observations of plasma density from multiple satellites have shown that the locations of the crests of the plasma density that are seen to be stationary during daytime are shifted after sunset. This phenomenon has been understood to be caused by eastward drift of the ionosphere at night. However, the eastward drift velocity of the ionosphere after sunset is not sufficiently large enough to explain the day-night difference in the longitudinal density structure. The just after sunset and the nighttime ionospheric morphologymay be affected by this drift after sunset. In this study, we will investigate the temporal variation of the phase of the longitudinal density structure and vertical plasma drift by analyzing the ROCSAT-1, TIMED/GUVI, and DMSP data and verify the role of the vertical drift after sunset in the change of the phase of the longitudinal density structure.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2002년도 한국우주과학회보 제11권1호
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• pp.56.1-56
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• 2002

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2009년도 한국우주과학회보 제18권1호
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• pp.41.1-41.1
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• 2009

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2001년도 한국우주과학회보 제10권2호
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• pp.65-65
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• 2001

• Journal of Astronomy and Space Sciences
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• 제33권1호
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• pp.29-36
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• 2016

The East African ionosphere (3°S-18°N, 32°E-50°E) was mapped using Total Electron Content (TEC) measurements from ground-based GPS receivers situated at Asmara, Mekelle, Bahir Dar, Robe, Arbaminch, and Nairobi. Assuming a thin shell ionosphere at 350 km altitude, we project the Ionospheric Pierce Point (IPP) of a slant TEC measurement with an elevation angle of >10° to its corresponding location on the map. We then infer the estimated values at any point of interest from the vertical TEC values at the projected locations by means of interpolation. The total number of projected IPPs is in the range of 24-66 at any one time. Since the distribution of the projected IPPs is irregularly spaced, we have used an inverse distance weighted interpolation method to obtain a spatial grid resolution of 1°×1° latitude and longitude, respectively. The TEC maps were generated for the year 2008, with a 2 hr temporal resolution. We note that TEC varies diurnally, with a peak in the late afternoon (at 1700 LT), due to the equatorial ionospheric anomaly. We have observed higher TEC values at low latitudes in both hemispheres compared to the magnetic equatorial region, capturing the ionospheric distribution of the equatorial anomaly. We have also confirmed the equatorial seasonal variation in the ionosphere, characterized by minimum TEC values during the solstices and maximum values during the equinoxes. We evaluate the reliability of the map, demonstrating a mean error (difference between the measured and interpolated values) range of 0.04-0.2 TECU (Total Electron Content Unit). As more measured TEC values become available in this region, the TEC map will be more reliable, thereby allowing us to study in detail the equatorial ionosphere of the African sector, where ionospheric measurements are currently very few.