한국우주과학회지

1121

지구자기구의 극초저주파수 파에 대한 RING CURRENT의 효과

김관혁
韓國宇宙科學會誌 = Journal of astronomy & space sciences
11, n.1
pp.93-106
1994
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지구자기구의 자기유체파에 대한 혼합의 성질을 연구하기 위해 3차원 box model을 개발하였다. 이 모델에서 축대칭 ring current의 효과를 자기유체파동방정식에 압력의 변화로 가정함으로써 조사하였다. 압축성 파는 축대칭 ring current에 의하여 noise가 발생되지만 자기력선 공명현상에는 어떠한 영향도 미치지 않는다느 사실을 발견하였다. 그러므로 압력 변화에 의한 ring current가 존재하는 지역에서 global 공동(cavity) mode 와 같이 불연속적인 주파수가 나타나지 않는 위성실험결과를 설명할 수 있었다. 또한 횡파의 연속적인 주파수 띠는 ring current가 지구의 이중극자축에 비대칭이 되어질 때 까지 영향을 받지 않음을 밝혔으며 따라서 실험결과에서 횡파에 의한 스펙트럼이 압축성파에 비해 매우 자주 관측됨을 확인할 수 있었다. 추가로 본 연구에서 압력의 변화를 가정하지 않은 이전의 box model이나 dipole model 에서 얻은 파 혼합현상의 결과가 유효함을 보였다.

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1122

H<TEX>$\bate$</TEX>CCD 측광의 정확도

김철희
韓國宇宙科學會誌 = Journal of astronomy & space sciences
11, n.2
pp.208-231
1994
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We have undertaken CCD observations of fie이 standard stars with H<TEX>$\beta$</TEX> photometric system to investigate the reliability of H<TEX>$\beta$</TEX> CCD photometry. Flat fielding with dome flat and sky flat for H<TEX>$\beta$</TEX>w and H<TEX>$\beta$</TEX>n filter was compared with that of B filter in UBV system and, from these, we have not found any difference. It was confirmed that there is a good linear relationship between our H<TEX>$\beta$</TEX> values observed with 2.3m reflector and standard values. However, H<TEX>$\beta$</TEX> values observed with 60cm reflector at Sobaeksan Astronomy Observatory showed very poor relationship. To investigate the accuracy of H<TEX>$\beta$</TEX> CCD photometry for fainter objects, open cluster NGC2437 was observed and reduced with DoPHOT, and the results were compared with those for photoelectric photometry of Stetson(1981).

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1123

THEORY AND SIMULATION OF BROADBAND ELECTROSTATIC NOISE IN THE MAGNETOTAIL

Kim, S.Y.
韓國宇宙科學會誌 = Journal of astronomy & space sciences
11, n.2
pp.250-272
1994
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Various plasma instabilities driven by the ion beams have been proposed in order to explain the broadband electrostatic noise (BEN) in the earth's geomagnetic tail. Ion acoustic, ion-ion two stream, and electron acoustic instabilities have been proposed. Here we consider a theoretical investigation of the generation of BEN by cold streaming ion beams in the earth's magnetotail. Linear theory analysis and particle simulation studies for the plasma sheet, which consists of warm electrons and ions as well as cold streaming ion beams, have been done. Both beam-ion acoustic and ion-ion two stream instabilities easily occur when the beam and warm electron temperature ratio, <TEX>$T_b/T_e$</TEX> is small enough. The numerical simulation results confirm the existence of broadband electrostatic noise whose frequency is ranged from <TEX>$\omega$</TEX>=0 to <TEX>$\omega$</TEX<TEX>$\omega_{pe}$</TEX>.

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1124

DETERMINING 3-D MOTION OF RIGID OBJECTS USING LINE CORRESPONDENCES

Kim, Won-Kyu
韓國宇宙科學會誌 = Journal of astronomy & space sciences
11, n.2
pp.273-280
1994
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A linear method for determining three-dimensional motion of a rigid object is presented. In this method, two three-dimensional line correspondences are used. By using three-dimensional information of the features and observing that the rotation is unique regardless of the translation vector, the two components of motion parameters (rotation and translation) are computed separately. Also in this paper, the solution is given without a scale factor which is necessary in other methods that use only the two-dimensional projective constraints.

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1125

UV ENERGY DISTRIBUTION OF AZ CASSIOPEIAE

Kang, Young-Woon
韓國宇宙科學會誌 = Journal of astronomy & space sciences
11, n.1
pp.31-40
1994
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The IUE low dispersion spectra of AZ Cas have been analyzed for line identifications and energy distribution in ultraviolet region. Highly ionized atoms, SiIV and CIV are identified. We could infer a temperature range of the B star between 15,000K and 20,000K. The energy density distribution shows a hump between IUE short wavelength and long wavelength regions. Photometric and spectroscopic elements were revised based on the Florkowisk photeelectric observations and collected radial velocities. The temperature of both stars were reduced as 16,000K and 3,800K. The radii of both stars are <TEX>$10 R_{\odot}\;and\;320R_{\odot}$</TEX>. The eccentricity and longitude of periastron are 0.61 and <TEX>$10.5^{\circ}$</TEX>, respectively.

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1126

UBV PHOTOMETRY AT THE OUTSIDE ECLIPSE PHASE OF AZ CASSIOPEIAE

Nha, Il-Seong
韓國宇宙科學會誌 = Journal of astronomy & space sciences
11, n.1
pp.21-30
1994
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VV Cep-type long period spectroscopic-eclipsing binary AZ Cas has been observed for five years, 1985 Oct~1990 Feb, UBV at the Ilsan Station of Yonsei University Observatory. A total of 431 observations (U=129, B=142 and V=160) are made for 86 nights. Instrumental differential UBV and B-V light curves made with these observations cover phases nearly a half of one period. There is no appreciable light variation in V but in other two passbands a gradual decrease of the brightness is clearly noticed. The loss of light in B resulted in a reddening in <TEX>$\Delta(B-V)$</TEX> by + 0.06 at phases between 0.4~0.5 as compared with that of at phase ~0.1. This intrinsic reddening arouses a question why at the orbital phase of the transit of a hot star in front of a cool M supergiant the heating of the facing hemisphere of M supergiant by the strong radiation from the B stat is absent. With regard to this unusual situation we propose a hypothesis that a large amount of gas stream of low temperature ejected from the surface of M supergiant component towards the B star dominates the brightness of B star and the reflection effect.

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1127

CCD를 이용한 변광성의 측광관측

정장해
韓國宇宙科學會誌 = Journal of astronomy & space sciences
11, n.2
pp.185-195
1994
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우리는 충북대학교가 보유하고 었는 <TEX>$1024\times1024$</TEX> pixel의 CCD 카메라를 이용하여 식변광성 U Cep를 1993년 1월 11-12일에 측광관측하였다. 이날 얻은 총 62개의 관측점을 가지고 제1극심 부근의 광도곡선을 완성하여 JD Hel 2448999.7274의 극심 시각을 결정하였다. 한편 1993년 10월 21-22일에 미국 네브라스카 대학의 Behlen 천문대에서 변광성 GW Cep와 V700 Cyg를 CCD 측광관측하여 총 168개의 관측점을 만들었다. 이들 자료를 가지고 광도곡선들을 완성하였고, GW Cep의 광도극심 시각 JD Hel 2449282.8485와 V700 Cyg의 광도극심 시각 JD Hel 2449282.7979을 각각 결정하였다. Behlen천문대의 CCD 관측방법과 충북대의 관측방법의 장단점을 비교하고 충북대 관측 방법의 개선을 위해 노출후 램에 기억되어 있는 CCD화상으로부터 직접 필요한 부분의 밝기만을 측정하고 이를 저장하는 방식의 개념을 제시하였다.

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1128

우리별 인공위성의 지상 촬영 장치에 쓰여진 렌즈의 MTF 측정

류광선
韓國宇宙科學會誌 = Journal of astronomy & space sciences
11, n.2
pp.320-326
1994
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한국과학기술원 인공위성 연구센터에서는 1992년 8월과 1993년 9월에 마이크로 위성인 우리별 1호와 2호를 발사, 운용중이다. 두 위성 모두에는 지표면을 촬영하기 위한 CCD 카메라가 실려있다. 이들 카메라에 쓰여진 렌즈(촛점거리: 50mm)를 평가하기 위해 MTF(Modulation Transfer Function) 측정을 하였다. 실험을 위해 표준과학연구소의 MTF 측정장치를 사용하였으며, f-number와 field angle을 변화시켜 가면서 측정하였다. 측정 결과로부터 f-number가 4.0 보다 작을때, 점광원으로부터 나온 빛이 CCD 칩의 한 화소(pixel) 안으로 들어 간다는 사실을 알 수 있었으며, field angle을 변화시켜가면서 tangential MTF와 sagital MTF를 측정한 결과, field angle이 증가함에 따라 MTF 값이 떨어짐을 알 수 있었다.

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1129

CHEMICAL COMPOSITION OF DUST GRAINS IN NOVAE

Suh, Kyung-Won
韓國宇宙科學會誌 = Journal of astronomy & space sciences
11, n.2
pp.165-174
1994
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We have investigated the chemical composition of dust grains in novae by computing the model spectra for the novae that showed temporary infrared developments shortly after their optical explosions. We find that a simple spherical dust shell models with hot blackbody central sources fit observations fairly well. Optical properties of dust grains deduced from modeling of AGB stars have been used for present calculations. We find that amorphous carbon grains appear to be the major infrared re-emission sources for the carbon-rich nova shells, and the silicate grains for the oxygen-rich nova shells.

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1130

MAGNETOSPHERIC STRUCTURE OF THE INTERMEDIATE POLAR

Kim, Yong-Gi
韓國宇宙科學會誌 = Journal of astronomy & space sciences
11, n.1
pp.1-12
1994
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The structure of the magnetic funnel element in the intermediate polar is considered in terms of an important site for the X-ray absorption and the reemission of the X-ray as the optical light. In this paper the column density and the optical depth vary with the filling factor, which is introduced to characterize the structure of matter in the magnetic funnel element. The results of the energy dependence of the X-ray spectrum and the modulation depth of the X-ray light curve are discussed.

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