• 천문학회보
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• 제37권2호
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• pp.134.1-134.1
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• 2012

The radiation belt structure can be approximately reproduced by a form of diffusion equation, which takes into account the radial diffusion process as well as those in pitch angle and energy. The solution of the equation depends on several factors including initial and boundary conditions, diffusion coefficients, and plasmapause location. In this paper, we have attempted to determine a set of approximate functions for the energetic electron fluxes near the outer edge of the outer belt in terms of solar wind variable. We used the electron flux data from SST onboard the THEMIS spacecraft and determined its correlation with solar wind conditions in a systematic way. The functions were determined separately for different energy channels from ~30 keV up to 719 keV. Our determination of these functions allows us to predict the radial boundary condition for the electron flux, which can be implemented in a forecast model.

• Journal of Astronomy and Space Sciences
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• 제18권2호
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• pp.109-118
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• 2001

1992년에 발사된 우리별 1호는 고에너지 양성자들이 OBC(On-Board Computer)186의 메모리에 SEU(Single Event Upset)을 일으키는 안쪽 반알렌대(Inner Van Allen Radiation Belt) 를 통과한다. 본 논문에서는 Chi-Square 방법을 이용하여 OBC(On-Board Compute.)186 메모리에서 측정된 SEU 데이터와 NASA/NSSDC의 AP-8 양성자 모델을 비교하여, SEU를 유발하게 되는 문턱 에너지를 추정해 보았다. OBC186위치에서의 양성자 선속을 유도하기 위해서 위성체에 의한 차폐 효과가 고려되었으며 모델의 신뢰성을 높이기 위해 태양 활동이 활발한 기간에 얻어진 데이터들은 제거되었다. 비교 결과 우리별 1호 OBC186 주 메모리의 문턱에너지는 $110{pm}10MeV$로 추정 되었다.

• Journal of Astronomy and Space Sciences
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• 제31권4호
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• pp.303-309
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• 2014

The Earth's outer radiation belt often suffers from drastic changes in the electron fluxes. Since the electrons can be a potential threat to satellites, efforts have long been made to model and predict electron flux variations. In this paper, we describe a prediction model for the outer belt electrons that we have recently developed at Chungbuk National University. The model is based on a one-dimensional radial diffusion equation with observationally determined specifications of a few major ingredients in the following way. First, the boundary condition of the outer edge of the outer belt is specified by empirical functions that we determine using the THEMIS satellite observations of energetic electrons near the boundary. Second, the plasmapause locations are specified by empirical functions that we determine using the electron density data of THEMIS. Third, the model incorporates the local acceleration effect by chorus waves into the one-dimensional radial diffusion equation. We determine this chorus acceleration effect by first obtaining an empirical formula of chorus intensity as a function of drift shell parameter $L^*$, incorporating it as a source term in the one-dimensional diffusion equation, and lastly calibrating the term to best agree with observations of a certain interval. We present a comparison of the model run results with and without the chorus acceleration effect, demonstrating that the chorus effect has been incorporated into the model to a reasonable degree.

• 천문학회보
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• 제38권2호
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• pp.95.2-95.2
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• 2013

The Van Allen Probes were designed to study the Earth's radiation belts on various scales of space and time. The identical two spacecrafts going nearly eccentric orbits lap each other several times over the course of the mission and each probe carries five instrument suites to address the science objectives on the radiation belt. Since Van Allen Probes launched on August 30, 2012, the probes detecte several storm events up to now. To understand the particle acceleration and loss mechanism in the radiation belt, we first focus on the energetic electrons' dynamics detected by ECT (Energetic Particle, Composition, and Thermal Plasma Suite). ECT measures near-Earth space's radiation particles covering the full electron and ion spectra from ~ eV to 10's of MeV with sufficient energy resolution. In this paper, we present the preliminary results of the recent several storm events using electron data from ECT(MagEIS and REPT).

• Journal of Astronomy and Space Sciences
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• 제36권2호
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• pp.45-60
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• 2019

The Earth's outer radiation belt has long received considerable attention mainly because the MeV electron flux in the belt varies often dramatically and at various time scales. It is now widely accepted that the wave-particle interaction is one of the major mechanisms responsible for such flux variations. The wave-particle interaction can accelerate electrons to MeV energies, explaining the observed flux increase events, and can also scatter the electrons' motion into the loss cone, resulting in atmospheric precipitation and thus contributing to flux dropouts. In this paper, we provide a review of the current state of research on relativistic electron scattering and precipitation due to the interaction with electromagnetic ion cyclotron (EMIC) waves in the inner magnetosphere. The review is intended to cover progress made over the last ~15 years in the theory and simulations of various issues, including quasilinear resonance diffusion, nonlinear interactions, nonresonant interactions, effects of finite normal angle on pitch angle scattering, effects due to rising tone emission, and ways to scatter near-equatorial pitch angle electrons. The review concludes with suggestions of a few promising topics for future research.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2000년도 한국우주과학회보 제9권1호
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• pp.17-17
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• 2000

No Abstract, See Full Text

• Journal of Astronomy and Space Sciences
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• 제39권4호
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• pp.145-158
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• 2022

The dynamics of the outer zone radiation belt has received a lot of attention mainly due to the correlation between the occurrence of enhancing relativistic electron flux and spacecraft operation anomalies or even failures (e.g., Baker et al. 1994). Relativistic electron events are often observed during great storms associated with ultra low frequency (ULF) waves. For example, a large buildup of relativistic electrons was observed during the great storm of March 24, 1991 (e.g., Li et al. 1993; Hudson et al. 1995; Mann et al. 2013). However, the dominant processes which accelerate magnetospheric radiation belt electrons to MeV energies are not well understood. In this paper, we present observations of Pc5 ULF waves in the recovery phase of the Bastille day storm of July 16, 2000 and electron and proton flux simultaneously oscillating with the same frequencies as the waves. The mechanism for the observed electron and proton flux modulations is examined using ground-based and satellite observations. During this storm time, multiple packets of discrete frequency Pc5 ULF waves appeared associated with energetic particle flux oscillations. We model the drift paths of electrons and protons to determine if the particles drift through the ULF wave to understand why some particle fluxes are modulated by the ULF waves and others are not. We also analyze the flux oscillations of electrons and protons as a function of energy to determine if the particle modulations are caused by a ULF wave drift resonance or advection of a particle density gradient. We suggest that the energetic electron and proton modulations by Pc5 ULF waves provide further evidence in support of the important role that ULF waves play in outer radiation belt dyanamics during storm times.

• 대한전자공학회논문지SD
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• 제45권3호
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• pp.1-5
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• 2008

본 논문은 고에너지 전자빔을 이용하여 저궤도 인공위성의 실리콘 태양센서의 내방사선 특성 변화를 분석하였다. 일반적으로 저궤도를 선회하는 위성은 반알렌대를 통과하며, 이 안에서 주기적인 운동으로 남극과 북극을 이동하는 하전입자에 의해 전자부품이 쉽게 손상되고 수명이 단축되는 등 악 영향을 받고 있다. 특히 방사선에 의한 SEU (Single Event Upset) 등은 인공위성에 탑재된 반도체 소자의 오동작 유발의 원인이 되고 있다. 본 논문은 한국원자력 연구원의 고에너지 ($300keV{\sim}1MeV$) 전자빔 조사장치를 이용하여 태양전지에 전자빔을 조사하고 이 때 변화되는 각각의 파라미터들에 대한 값을 측정하고자 한다. 이러한 연구는 저궤도 인공위성에서 전력을 생산하기 위해서 사용하는 전력용 태양 전지의 방사능 영향을 이해하는 데도 많은 영향을 줄 수 있을 것으로 기대된다.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.1191-1196
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• 2006

Analysis of drying characteristics has been carried out with one-dimensional model in the dryer using the principle of the refraction of radiation. The dryer is composed of hot water tank, a plastic film conveyer belt, drying material, etc. The model considers the conduction and radiation within the plastic film and drying material. The film is semitransparent to radiation and the drying material is assumed to be semitransparent or opaque to radiation. The results shows that the effect of radiative transfer on the drying rate is relatively large when the thickness of drying material is small and the water temperature is high. When the material is thin, the drying rate by only conduction is also enhanced so that drying time can considerably be reduced.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2003년도 춘계학술발표대회 요약집
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• pp.333.1-333.1
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• 2003