극지연구소에서의 극지 우주환경 및 고층대기 연구 현황

지건화 한국전자파학회 2015 전자파기술 Vol.26 No.4

Ground-based Observations for the Upper Atmosphere at King Sejong Station, Antarctica

지건화,김정한,김용하 한국우주과학회 2014 Journal of Astronomy and Space Sciences Vol.31 No.2

Since the operation of the King Sejong Station (KSS) started in Antarctic Peninsula in 1989, there have been continuousefforts to perform the observation for the upper atmosphere. The observations during the initial period of the stationinclude Fabry-Perot Interferometer (FPI) and Michelson Interferometer for the mesosphere and thermosphere, which areno longer in operation. In 2002, in collaboration with York University, Canada, the Spectral Airglow Temperature Imager(SATI) was installed to observe the temperature in the mesosphere and lower thermosphere (MLT) region and it has stillbeen producing the mesopause temperature data until present. The observation was extended by installing the meteorradar in 2007 to observe the neutral winds and temperature in the MLT region during the day and night in collaborationwith Chungnam National University. We also installed the all sky camera in 2008 to observe the wave structures in the MLTregion. All these observations are utilized to study on the physical characteristics of the MLT region and also on the wavephenomena such as the tide and gravity wave in the upper atmosphere over KSS that is well known for the strong gravitywave activity. In this article, brief introductions for the currently operating instruments at KSS will be presented with theirapplications for the study of the upper atmosphere.

자기폭풍이 일어나면 이온권에서는 "보통" 어떤 일이 생길까?

지건화 한국우주과학회 2009 한국우주과학회보 Vol.18 No.2

우주기상현상에서 자기폭풍은 태양으로부터 태양풍, 지구 자기권, 고층대기를 모두 포함하는 매우 복잡한 현상인데, 이들 중 자기폭풍이 고층대기 이온권에 미치는 영향에서도 매우 복잡하고 다양한 모습으로 나타난다. 자기폭풍이 이온권에 미치는 영향의 연구는 대부분 어떤 특정한 자기폭풍이 일어났을 때 이온권에 나타나는 변화의 관측자료 분석이나 모델링을 통한 연구이다. 그러나 이러한 연구는 자기폭풍이 일어나면 보통 이온권에는 어떤 변화가 일어나는지에 대한 답을 주지는 못한다. 한편, 이온권은 시간, 위치, 태양 및 지자기 활동 등의 변화에 따라 일반적인 변화경향을 보일 수 있는데, 이러한 물리적 조건 중 지자기활동이 변화할 때, 즉 자기폭풍이 발생할 때 이온권이 어떤 변화를 보이는지에 대한 일반적인 경향은 아직 정확히 알려져 있지 않다. 이는 자기폭풍의 영향이 다양한 조건에서 대단히 복잡한 패턴을 가지고 있어 간단히 일반화하기 어렵기 때문인데, 장기간의 이온권 관측 자료를 이용하여 체계적인 분석을 통해 자기폭풍이 얼어났을 때 공통으로 나타나는 이온권 변화를 연구할 수 있을 것으로 기대된다. 최근 인공위성을 이용하여 장기간에 걸쳐 전 지구적인 이온권 관측이 수행되고 있는데, GPS나 TOPEX/JASON 위성 등에서 이온권 총 전자량이 관측되고 있다. 향후 이러한 관측 자료의 체계적인 분석을 통해 자기폭풍에 의한 이온권 변화의 일반적인 경향을 체계화 할 수 있을 것으로 기대된다.

Seasonal Characteristics of the Longitudinal Wavenumber-4 Structure in the Equatorial Ionospheric Anomaly

김어진,지건화,김용하 한국우주과학회 2008 Journal of Astronomy and Space Sciences Vol.25 No.4

Using the global total electron contents (TEC) measured by the TOPEX satellite from Aug. 1992 to Oct. 2005, we investigate the variations of the longitudinal wavenumber-4 (LW-4) structure in the equatorial anomaly (EA) crests with season, local time, and solar activity. Our study shows that the LW-4 structure in the EA crests (5$\sim$20{$^\circ$} MLAT in both hemispheres) has clear four peaks at fixed longitude sectors during the daytime for both equinoxes and June solstice. In spite of being called a wavelike structure, however, the magnitudes and spatial intervals of the four peaks are far from being the same or regular. After sunset, the four-peak structure begins to move eastward with gradual weakening in its amplitude during equinoxes and this weakening proceeds much faster during June solstice. Interestingly, the longitudinal variations during December solstice do not show clear four-peak structure. All these features of the LW-4 structure are almost the same for both low and high solar activity conditions although the ion densities are greatly enhanced from low to high solar activities. With the irrelevancy of the magnetic activity in the LW-4, this implies that the large changes of the upper atmospheric ion densities, one of the important factors for ion-neutral interactions, have little effect on the formation of the LW-4 structure. On the other hand, we found that the monthly variation of the LW-4 is remarkably similar to that of the zonal component of wavenumber-3 diurnal tides at low latitudes, which implies that the lower atmospheric tidal forcing, transferred to the upper atmosphere, seems to have a dominant role in producing the LW-4 structure in the EA crests via the E-region dynamo.

2003년 지자기 폭풍 동안 한반도 상공 전리층 폭풍 관측

정종균,지건화,김어진,김용하,조정호 한국우주과학회 2009 한국우주과학회보 Vol.18 No.2

지자기 폭풍이 발생할 동안 중위도 전리권 전자밀도 변화의 가장 큰 특징은 양전리권 폭풍 또는 음전리권 폭풍이다. 양전리층 폭풍은 정상적인 경우보다 전자밀도가 증가하는 것으로 정의되는데 적도방향 중성바람에 의한 극지방 전자밀도의 중위도로의 이동으로 설명된다. 음전리권 폭풍은 F2 층 고도의 O/N2 증가에 의한 전자소멸로 전자밀도가 낮아지는 것으로 알려져 있다. 우리는 지상 GPS 총전자량 자료와 이를 이용한 전리권 토모그래피 모델 결과, 그리고 이온존데 관측에 나타난 한반도 상공의 전리층 폭풍 양상을 제시하고 토의할 것이다.

Global Positioning System Total Electron Content Variation over King Sejong Station in Antarctic under the Solar Minimum Condition Between 2005 and 2009

정종균,지건화,이지나 한국우주과학회 2011 Journal of Astronomy and Space Sciences Vol.28 No.4

The total electron content (TEC) using global positioning system (GPS) is analyzed to see the characteristics of ionosphere over King Sejong station (KSJ, geographic latitude 62°13′ S, longitude 58° 47′ W, corrected geomagnetic latitude 48° S) in Antarctic. The GPS operational ratio during the observational period between 2005 and 2009 is 90.1%. The annual variation of the daily mean TEC decreases from January 2005 to February 2009, but increase from the June 2009. In summer (December-February), the seasonal mean TEC values have the maximum of 26.2 ± 2.4 TEC unit (TECU) in 2005 and the minimum of 16.5 ± 2.8 TECU in 2009, and the annual differences decrease from 3.0 TECU (2005-2006) to 1.4 TECU (2008-2009). However, on November 2010, it significantly increases to 22.3 ± 2.8 TECU which is up to 5.8 TECU compared with 2009 in summer. In winter (June-August), the seasonal mean TEC slightly decreases from 13.7 ± 4.5 TECU in 2005 to 8.9 ± 0.6 TECU in 2008, and the annual difference is constantly about 1.6 TECU, and increases to 10.3 ± 1.8 TECU in 2009. The annual variations of diurnal amplitude show the seasonal features that are scattered in summer and the enhancements near equinoxes are apparent in the whole years. In contrast, the semidiurnal amplitudes show the disturbed annual peaks in winter and its enhancements near equinoxes are unapparent. The diurnal phases are not constant in winter and show near 12 local time (LT). The semidiurnal phases have a seasonal pattern between 00 LT and 06 LT. Consequently, the KSJ GPS TEC variations show the significant semidiurnal variation in summer from December to February under the solar minimum between 2005 and 2009. The feature is considered as the Weddell Sea anomaly of larger nighttime electron density than a daytime electron density that has been observed around the Antarctica peninsula.

Tidal features seen in Total Electron Contents from TOPEX/POSEIDON MISSION

김어진,김용하,지건화 한국천문학회 2007 天文學會報 Vol.32 No.2

Ground-based Observations of the Polar Region Space Environment at the Jang Bogo Station, Antarctica

권혁진,이창섭,지건화,함영배,김정한,김용하,김관혁,Qian Wu,Terence Bullett,오수연,곽영실 한국우주과학회 2018 Journal of Astronomy and Space Sciences Vol.35 No.3

Jang Bogo Station (JBS), the second Korean Antarctic research station, was established in Terra Nova Bay, Antarctica (74.62°S 164.22°E) in February 2014 in order to expand the Korea Polar Research Institute (KOPRI) research capabilities. One of the main research areas at JBS is space environmental research. The goal of the research is to better understand the general characteristics of the polar region ionosphere and thermosphere and their responses to solar wind and the magnetosphere. Ground-based observations at JBS for upper atmospheric wind and temperature measurements using the Fabry-Perot Interferometer (FPI) began in March 2014. Ionospheric radar (VIPIR) measurements have been collected since 2015 to monitor the state of the polar ionosphere for electron density height profiles, horizontal density gradients, and ion drifts. To investigate the magnetosphere and geomagnetic field variations, a search-coil magnetometer and vector magnetometer were installed in 2017 and 2018, respectively. Since JBS is positioned in an ideal location for auroral observations, we installed an auroral all-sky imager with a color sensor in January 2018 to study substorms as well as auroras. In addition to these observations, we are also operating a proton auroral imager, airglow imager, global positioning system total electron content (GPS TEC)/scintillation monitor, and neutron monitor in collaboration with other institutes. In this article, we briefly introduce the observational activities performed at JBS and the preliminary results of these observations.

전천 카메라와 페브리-페로 간섭계 자료를 이용한 한반도 상공 중간권 중량파의 고유파동계수 및 운동량 플럭스 산출

정종균,김용하,원영인,지건화 한국우주과학회 2007 Journal of Astronomy and Space Sciences Vol.24 No.4

남극 세종기지에 위치한 SATI (Spectral Airglow Temperature Imager) 및 VHF Meteor Radar 관측을 통한 중간권 상부의 온도 비교

김정한,김용하,정종균,원영인,지건화,이방용 한국우주과학회 2007 한국우주과학회보 Vol.16 No.1