• 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

• Journal of Astronomy and Space Sciences
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• 제23권3호
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• pp.237-244
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• 2006

한국천문연구원에서 운영중인 9개의 GPS(Global Positioning System) 상시관측소 데이터를 이용하여 한반도 상공의 고도에 따른 전리층 내의 전자밀도 분포를 산출하였다. 전리층의 전자 밀도를 정밀하게 추정하기 위해 이중주파수(L1,L2) 데이터가 사용되었고, 2차원 총전자수(Total Electron Contents, TEC)값을 기반으로 정밀한 전자 밀도 분포를 얻을 수 있었다. 그리고 토모그래피 모델개발에 널리 사용되고 있는 Inversion 기법 중의 하나인 ART(Algebraic Reconstruction Technique) 알고리즘을 적용하였다. 본 연구에서는 지역적 GPS 관측망을 활용하여 시간에 따른 한반도 상공의 전자밀도 분포 유형을 제시하였고, GPS에 의한 전리층 재구성으로 얻어진 전자밀도 유형을 경험적 모델인 IRI-2001에 의해 계산된 값과 관측으로부터 얻어진 Ionosonde 관측값을 서로 비교하였다. 그 결과 GPS 재구성에 의한 전자밀도 분포 유형이 Ionosonde에 의한 관측값과 잘 일치하는 경향을 보였다.

• 한국통신학회논문지
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• 제36권5A호
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• pp.529-535
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• 2011

HF 통신은 별도의 중계 없이 근거리 및 장거리 통신이 가능한 방법으로 해외에서는 주/부 통신수단으로 활용되고 있으나, 국내에서는 도약지대 극복 문제와 전리층 변화에 따라 사용가능한 주파수가 변한다는 이유로 사용자 기피 현상이 심화된 상태였다. NVIS 통신은 일반적인 전리층 반사 통신에 비해 잡음이 적고 도약지대를 포함한 근거리내에서도 통신이 가능한 방법으로써, 이번 연구를 통해 HF 통신의 기존 단점들을 극복하고 HF 통신의 활성화를 위해 외국의 NVIS 통신방법에 대해서 실험을 통해 검증해 보았다. 본 논문에서는 NVIS 통신의 개념을 설명하고, 실제 국내의 HF 통신운용 현황을 확인하였다. 이를 바탕으로 NVIS 통신의 도약지대 극복가능성을 검증하였으며, 효율적인 HF 통신을 위한 예측프로그램의 적용가능성도 판단해보았다.

• Journal of Astronomy and Space Sciences
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• 제35권3호
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• pp.143-149
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• 2018

The ionosphere has been monitored by ionosondes for over five decades since the 1960s in Korea. An ionosonde typically produces an ionogram that displays radio echoes in the frequency-range plane. The trace of echoes in the plane can be read either manually or automatically to derive useful ionospheric parameters such as foF2 (peak frequency of the F2 layer) and hmF2 (peak height of the F2 layer). Monitoring of the ionosphere should be routinely performed in a given time cadence, and thus, automatic scaling of an ionogram is generally executed to obtain ionospheric parameters. However, an auto-scaling program can generate undesirable results that significantly misrepresent the ionosphere. In order to verify the degree of misrepresentation by an auto-scaling program, we performed manual scaling of all 35,136 ionograms measured at Jeju ($33.43^{\circ}N$, $126.30^{\circ}E$) throughout 2012. We compared our manually scaled parameters (foF2 and hmF2) with auto-scaled parameters that were obtained via the ARTIST5002 program. We classified five cases in terms of the erroneous scaling performed by the program. The results of the comparison indicate that the average differences with respect to foF2 and hmF2 between the two methods approximately correspond to 0.03 MHz and 4.1 km, respectively with corresponding standard deviations of 0.12 MHz and 9.58 km. Overall, 36 % of the auto-scaled results differ from the manually scaled results by the first decimal number. Therefore, future studies should be aware of the quality of auto-scaled parameters obtained via ARTIST5002. Hence, the results of the study recommend the use of manually scaled parameters (if available) for any serious applications.

• 천문학회지
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• 제45권2호
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• pp.39-48
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• 2012

We investigate non-LTE effects on the $H_3^+$ level populations to help the analysis of the observed 2 and 3.5 micron $H_3^+$ emissions from the Jovian ionosphere. We begin by constructing a simple three-level model, in order to compute the intensity ratio of the R(3,4) line in the hot band to the Q(1,0) line in the fundamental band, which have been observed in the Jovian auroral regions. We find that non-LTE effects produce only small changes in the intensity ratios for ambient $H_2$ densities less than or equal to $5{\times}10^{11}cm^{-3}$. We then construct two comprehensive models by including all the collisional and radiative transitions between pairs of more than a thousand known $H_3^+$ rovibrational levels with energies less than 10000 $cm^{-1}$. By employing these models, we find that the intensity ratios of the lines in the hot and fundamental bands are affected greatly by non-LTE effects, but the details depend sensitively on the number of collisional and radiative transitions included in the models. Non-LTE effects on the rovibrational population become evident at about the same ambient $H_2$ densities in the comprehensive models as in the three-level model. However, the models show that rotational temperatures derived from the intensities of rotational lines in the ${\nu}_2$ and $2{\nu}_2$ bands may differ significantly from the ambie temperatures in the non-LTE regime. We find that significant non-LTE effects appear near and above the $H_3^+$ peak, and that the kinetic temperatures in the Jovian thermospheric temperatures derived from the observed line ratios in the 2 and 3.5 micron $H_3^+$ emissions are highly model dependent.

• Journal of Astronomy and Space Sciences
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• 제34권4호
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• pp.343-352
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• 2017

A space plasma facility has been operated with a back-diffusion-type plasma source installed in a mid-sized vacuum chamber with a diameter of ~1.5 m located in Satellite Technology Research Center (SaTReC), Korea Advanced Institute of Science and Technology (KAIST). To generate plasma with a temperature and density similar to the ionospheric plasma, nickel wires coated with carbonate solution were used as filaments that emit thermal electrons, and the accelerated thermal electrons emitted from the heated wires collide with the neutral gas to form plasma inside the chamber. By using a disk-type Langmuir probe installed inside the vacuum chamber, the generation of plasma similar to the space environment was validated. The characteristics of the plasma according to the grid and plate anode voltages were investigated. The grid voltage of the plasma source is realized as a suitable parameter for manipulating the electron density, while the plate voltage is suitable for adjusting the electron temperature. A simple physical model based on the collision cross-section of electron impact on nitrogen molecule was established to explain the plasma generation mechanism.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2010년도 한국우주과학회보 제19권1호
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• pp.30.3-31
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• 2010

We performed a comprehensive comparison between GPS Global Ionosphere Map (GIM) and TOPEX/Jason (T-J) TEC data for the periods of 1998~2009 in order to assess the performance of GIM over the global ocean where the GPS ground stations are very sparse. Using the GIM model constructed by CODE at University of Bern, the GIM TEC values were obtained along the T-J satellite orbit at the locations and times of the measurements and then binned into various geophysical conditions for direct comparison with the T-J TECs. On the whole, the GIM model was able to reproduce the spatial and temporal variations of the global ionosphere as well as the seasonal variations. However, the GIM model was not accurate enough to represent the well-known ionospheric structures such as the equatorial anomaly, the Weddell Sea Anomaly, and the longitudinal wave structure. Furthermore, there seems to be a fundamental limitation of the model showing the unexpected negative differences (i.e., GPS < T-J) in the northern high latitude and the southern middle and high latitude regions. The positive relative differences (i.e., GIM > T-J) at night represent the plasmaspheric contribution to GPS TEC, which is maximized, reaching up to 100% of the corresponding T-J TEC values in the early morning sector. In particular, the relative differences decreased with increasing solar activity and this may indicate that the plasmaspheric contribution to the maintenance of the nighttime ionosphere does not increase with solar activity, which is different from what we normally anticipate. Among these results, the plasmaspheric contribution to the ionospheric GPS TEC will be presented in this talk and the rest of it will presented in the companion paper (poster presentation).

• 융합보안논문지
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• 제18권2호
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• pp.77-88
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• 2018

본 연구의 목적은 기상조절기술의 군사적 활용방안을 연구하고, 한반도 환경 및 기술수준 등을 고려하여 연구의 우선순위를 과학적인 기법으로 도출하는데 있다. 이를 위해 각 기술들을 군사적으로 이용할 경우 장점과 단점을 살펴보고, 전문가 집단을 구성하여 델파이 기법을 통해 우선순위 평가를 위한 지표를 도출하였으며, 분석적계층분석 기법을 통해 평가지표의 가중치와 각 평가지표 내에서의 기술들의 가중치를 유도하여 최종적인 연구 우선순위를 정하였다. 분석결과 전리층 변조 기술이 무기체계로서의 효과성과 한반도 환경에서의 적합성 측면에서 가장 큰 우선순위가 있는 것으로 나타났다. 현재 북한의 전자전 및 미사일 위협 등을 고려할 때 전리층 변조 기술은 기상전의 일부로써 우선적인 확보가 필요하며, 통일 이후의 잠재적 주변국 위협에 대응하기 위해서는 전리층 변조뿐만 아니라 군사 과학기술 선진국들과의 기술적 격차가 있는 인공강우(설), 낙뢰유도, 안개 소산 기술도 민간기술의 적극적인 활용(Spin-On)을 통해 기반을 구축해야 할 시기이다.

• Journal of Astronomy and Space Sciences
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• 제39권3호
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• pp.117-126
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• 2022

The Ionospheric Anomaly Monitoring by Magnetometer And Plasma-probe (IAMMAP) is one of the scientific instruments for the Compact Advanced Satellite 500-3 (CAS 500-3) which is planned to be launched by Korean Space Launch Vehicle in 2024. The main scientific objective of IAMMAP is to understand the complicated correlation between the equatorial electro-jet (EEJ) and the equatorial ionization anomaly (EIA) which play important roles in the dynamics of the ionospheric plasma in the dayside equator region. IAMMAP consists of an impedance probe (IP) for precise plasma measurement and magnetometers for EEJ current estimation. The designated sun-synchronous orbit along the quasi-meridional plane makes the instrument suitable for studying the EIA and EEJ. The newly-devised IP is expected to obtain the electron density of the ionosphere with unprecedented precision by measuring the upper-hybrid frequency (f_UHR) of the ionospheric plasma, which is not affected by the satellite geometry, the spacecraft potential, or contamination unlike conventional Langmuir probes. A set of temperature-tolerant precision fluxgate magnetometers, called Adaptive In-phase MAGnetometer, is employed also for studying the complicated current system in the ionosphere and magnetosphere, which is particularly related with the EEJ caused by the potential difference along the zonal direction.