• Title/Summary/Keyword: solar observation

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Distributions of temperature and salinity in relation to ebb, turn of tide and flood of the Bottol Bada in July, 2004 (2004년 7월 봇돌바다의 썰물, 전류 및 밀물시 수온과 염분 분포)

  • Choi Yong-Kyu;Cho Eun-Seob;Lee Yong-Hwa;Lee Young-Sik
    • Journal of Environmental Science International
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    • v.14 no.2
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    • pp.167-175
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    • 2005
  • Based on the observation on 20, 23 and 26 July 2004, the distributions of temperature, salinity and stratification was investigated in relation to ebb, turn of tide and flood. The results are as follows: I) The high temperature and low saline water with $23.5\~24.0^{\circ}C\;and\;32.4\~33.0psu$ existed at Naro Island. 2) The cold surface water below $21.0^{\circ}C\;and\;33.0\~33.4psu$ appeared in the area near Gae Island and Geumo Island. 3) The cold and saline water, below $24.0^{\circ}C$ at the surface and $17.0^{\circ}C$ near the bottom, $32.8\~33.8psu$ at the surface and $33.8\~34.0psu$ near the bottom, existed in Sori Island. These waters were more saline compared to the South Sea Coastal Water with about 31.8psu. This suggests that the oceanic saline water intruded into the Bottol Bada through the area near Sori Island. The stratification appeared during all the observation periods due to a high solar radiation of $22MJ/m^2$, and a weak wind speed of 2.9m/s on the average while the mean speed of wind in July is around 3.9 m/s. It qualitatively suggested that the stratification was maintained during the observation periods because of a high solar radiation, a weak wind speed and intrusion of saline oceanic water.

Observation and Analysis of the Long and Short Wave Radiation According to Different Altitudes and Locations in Daegu During Summer (대구지역의 고도와 위치에 따른 하절기 장·단파복사 관측과 해석)

  • Choi, Dong-Ho;Lee, Bu-Yong;Oh, Ho-Yeop
    • Journal of the Korean Solar Energy Society
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    • v.32 no.4
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    • pp.71-81
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    • 2012
  • This study for the understanding of the radiation environment according to the altitude in urban area in the summer observes the long and short wave radiation environment at the 4 urban areas with different height and the 1 suburban area. The results of this study are as follows. (1) When the altitude was high, the more short wave radiation was observed. (2) As the altitude was high, the temperature of atmosphere got lower. And because of that the downward long wave radiation was also lower. This general trend was confirmed through the study. (3) Through the observation of long wave radiation, the upper atmosphere of suburban area had the atmosphere characteristic which the temperature was rising and decreasing faster. Therefore, the difference radiation characteristics between the urban and suburban area were confirmed. (4) The result of the ratio of short wave radiation to long wave radiation(short wave radiation/long wave radiation) according to the altitude and location, the value was increased when the distance was far from the artificiality structure or a heat source, and the urban effect became smaller. Thus, it is expected that the ratio will be an evaluation index for evaluating urbanization effect.

DEEP-South: Round-the-Clock Physical Characterization and Survey of Small Solar System Bodies in the Southern Sky

  • Moon, Hong-Kyu;Kim, Myung-Jin;Roh, Dong-Goo;Park, Jintae;Yim, Hong-Suh;Choi, Young-Jun;Bae, Young-Ho;Lee, Hee-Jae;Oh, Young-Seok
    • The Bulletin of The Korean Astronomical Society
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    • v.41 no.1
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    • pp.54.2-54.2
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    • 2016
  • Korea Microlensing Telescope Network (KMTNet) is the first optical survey system of its kind in a way that three KMTNet observatories are longitudinally well-separated, and thus have the benefit of 24-hour continuous monitoring of the southern sky. The wide-field and round-the-clock operation capabilities of this network facility are ideal for survey and the physical characterization of small Solar System bodies. We obtain their orbits, absolute magnitudes (H), three dimensional shape models, spin periods and spin states, activity levels based on the time-series broadband photometry. Their approximate surface mineralogy is also identified using colors and band slopes. The automated observation scheduler, the data pipeline, the dedicated computing facility, related research activity and the team members are collectively called 'DEEP-South' (DEep Ecliptic Patrol of Southern sky). DEEP-South observation is being made during the off-season for exoplanet search, yet part of the telescope time is shared in the period between when the Galactic bulge rises early in the morning and sets early in the evening. We present here the observation mode, strategy, software, test runs, early results, and the future plan of DEEP-South.

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An Analysis of Observational Environments for Solar Radiation Stations of Korea Meteorological Administration using the Digital Elevation Model and Solar Radiation Model (수치표고모델과 태양복사모델을 이용한 기상청 일사 관측소 관측환경 분석)

  • Jee, Joon-Bum;Zo, Il-Sung;Kim, Bu-Yo;Lee, Kyu-Tae
    • Journal of the Korean earth science society
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    • v.40 no.2
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    • pp.119-134
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    • 2019
  • In order to analyze the observational environment of solar radiation stations operated by the Korea Meteorological Administration (KMA), we used the digital elevation model (DEM) and the solar radiation model to calculate a topographical shading, sky view factor (SVF) and solar radiation by surrounding terrain. The sky line and SVF were calculated using high resolution DEM around 25 km of the solar stations. We analyzed the topographic effect by analyzing overlapped solar map with sky line. Particularly, Incheon station has low SVF whereas Cheongsong and Chupungryong station have high SVF. In order to validation the contribution of topographic effect, the solar radiation calculated using GWNU solar radiation model according to the sky line and SVF under the same meteorological conditions. As a result, direct, diffuse and global solar radiation were decreased by 12.0, 5.6, and 4.7% compared to plane surface on Cheongsong station. The 6 stations were decreased amount of mean daily solar radiation to the annual solar radiation. Among 42 stations, eight stations were analyzed as the urgent transfer stations or moving equipment quickly and more than half of stations (24) were required to review the observational environment. Since the DEM data do not include artifacts and vegetation around the station, the stations need a detail survey of observational environment.

TOWARD A NEXT GENERATION SOLAR CORONAGRAPH: DEVELOPMENT OF A COMPACT DIAGNOSTIC CORONAGRAPH FOR THE ISS

  • Cho, K.S.;Bong, S.C.;Choi, S.;Yang, H.;Kim, J.;Baek, J.H.;Park, J.;Lim, E.K.;Kim, R.S.;Kim, S.;Kim, Y.H.;Park, Y.D.;Clarke, S.W.;Davila, J.M.;Gopalswamy, N.;Nakariakov, V.M.;Li, B.;Pinto, R.F.
    • Journal of The Korean Astronomical Society
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    • v.50 no.5
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    • pp.139-149
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    • 2017
  • The Korea Astronomy and Space Science Institute plans to develop a coronagraph in collaboration with National Aeronautics and Space Administration (NASA) and to install it on the International Space Station (ISS). The coronagraph is an externally occulted one-stage coronagraph with a field of view from 3 to 15 solar radii. The observation wavelength is approximately 400 nm, where strong Fraunhofer absorption lines from the photosphere experience thermal broadening and Doppler shift through scattering by coronal electrons. Photometric filter observations around this band enable the estimation of 2D electron temperature and electron velocity distribution in the corona. Together with a high time cadence (<12 min) of corona images used to determine the geometric and kinematic parameters of coronal mass ejections, the coronagraph will yield the spatial distribution of electron density by measuring the polarized brightness. For the purpose of technical demonstration, we intend to observe the total solar eclipse in August 2017 with the filter system and to perform a stratospheric balloon experiment in 2019 with the engineering model of the coronagraph. The coronagraph is planned to be installed on the ISS in 2021 for addressing a number of questions (e.g., coronal heating and solar wind acceleration) that are both fundamental and practically important in the physics of the solar corona and of the heliosphere.

PARALLEL IMAGE RECONSTRUCTION FOR NEW VACUUM SOLAR TELESCOPE

  • Li, Xue-Bao;Wang, Feng;Xiang, Yong Yuan;Zheng, Yan Fang;Liu, Ying Bo;Deng, Hui;Ji, Kai Fan
    • Journal of The Korean Astronomical Society
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    • v.47 no.2
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    • pp.43-47
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    • 2014
  • Many advanced ground-based solar telescopes improve the spatial resolution of observation images using an adaptive optics (AO) system. As any AO correction remains only partial, it is necessary to use post-processing image reconstruction techniques such as speckle masking or shift-and-add (SAA) to reconstruct a high-spatial-resolution image from atmospherically degraded solar images. In the New Vacuum Solar Telescope (NVST), the spatial resolution in solar images is improved by frame selection and SAA. In order to overcome the burden of massive speckle data processing, we investigate the possibility of using the speckle reconstruction program in a real-time application at the telescope site. The code has been written in the C programming language and optimized for parallel processing in a multi-processor environment. We analyze the scalability of the code to identify possible bottlenecks, and we conclude that the presented code is capable of being run in real-time reconstruction applications at NVST and future large aperture solar telescopes if care is taken that the multi-processor environment has low latencies between the computation nodes.

Observation of an Ellerman bomb and its associated surge with the 1.6 meter New Solar Telescope at Big Bear Solar Observatory

  • Yang, Heesu;Chae, Jongchul;Park, Hyungmin;Maurya, Ram Ajor;Cho, Kyuhyun;Kim, Yeon-Han;Cho, Il-Hyun;Lim, Eun-Kyung
    • The Bulletin of The Korean Astronomical Society
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    • v.37 no.2
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    • pp.111.2-111.2
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    • 2012
  • We observed an Ellerman bomb(EB) and its associated surge using the Fast Imaging Solar Spectrograph(FISS) and the broadband TiO filter of the 1.6 meter New Solar Telescope at Big Bear Solar Observatory. As is well-known, the EB appears as a feature that is very bright at the far wings of the H alpha line. The lambdameter method applied to these wings indicates that the EB is blue-shifted up to 6km/s in velocity. In the photospheric level below the EB, we see rapidly growing "granule-like" feature. The transverse velocity of the dark lane at the edge of the "granule" increased with time as reached a peak of 6km/s, at the time of the EB's occurrence. The surge was seen in absorption and varied rapidly both in the H alpha and the Ca II 8542 line. It originated from the Ellerman bomb, and was impulsively accelerated to 20km/s toward us(blueshift). Then the velocity of the surge gradually changed from blueshift of 20km/s to redshift of 40km/s. By adopting the cloud model, we estimated the temperature of the surge material at about 27000K and the non-thermal velocity at about 10km/s. Our results shed light on the conventional idea that an EB results from the magnetic reconnection of an emerging flux tube and pre-existing field line.

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Evaluation of UM-LDAPS Prediction Model for Solar Irradiance by using Ground Observation at Fine Temporal Resolution (고해상도 일사량 관측 자료를 이용한 UM-LDAPS 예보 모형 성능평가)

  • Kim, Chang Ki;Kim, Hyun-Goo;Kang, Yong-Heack;Kim, Jin-Young
    • Journal of the Korean Solar Energy Society
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    • v.40 no.5
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    • pp.13-22
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    • 2020
  • Day ahead forecast is necessary for the electricity market to stabilize the electricity penetration. Numerical weather prediction is usually employed to produce the solar irradiance as well as electric power forecast for longer than 12 hours forecast horizon. Korea Meteorological Administration operates the UM-LDAPS model to produce the 36 hours forecast of hourly total irradiance 4 times a day. This study interpolates the hourly total irradiance into 15 minute instantaneous irradiance and then compare them with observed solar irradiance at four ground stations at 1 minute resolution. Numerical weather prediction model employed here was produced at 00 UTC or 18 UTC from January to December, 2018. To compare the statistical model for the forecast horizon less than 3 hours, smart persistent model is used as a reference model. Relative root mean square error of 15 minute instantaneous irradiance are averaged over all ground stations as being 18.4% and 19.6% initialized at 18 and 00 UTC, respectively. Numerical weather prediction is better than smart persistent model at 1 hour after simulation began.

Martian Bow Shock and Magnetic Pile-Up Barrier Formation Due to the Exosphere Ion Mass-Loading

  • Kim, Eo-Jin;Sohn, Jong-Dae;Yi, Yu;Ogino, Tatsuki;Lee, Joo-Hee;Park, Jae-Woo;Song, Young-Joo
    • Journal of Astronomy and Space Sciences
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    • v.28 no.1
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    • pp.17-26
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    • 2011
  • Bow shock, formed by the interaction between the solar wind and a planet, is generated in different patterns depending on the conditions of the planet. In the case of the earth, its own strong magnetic field plays a critical role in determining the position of the bow shock. However, in the case of Mars of which has very a small intrinsic magnetic field, the bow shock is formed by the direct interaction between the solar wind and the Martian ionosphere. It is known that the position of the Martian bow shock is affected by the mass loading-effect by which the supersonic solar wind velocity becomes subsonic as the heavy ions originating from the planet are loaded on the solar wind. We simulated the Martian magnetosphere depending on the changes of the density and velocity of the solar wind by using the three-dimensional magnetohydrodynamic model built by modifying the comet code that includes the mass loading effect. The Martian exosphere model of was employed as the Martian atmosphere model, and only the photoionization by the solar radiation was considered in the ionization process of the neutral atmosphere. In the simulation result under the normal solar wind conditions, the Martian bow shock position in the subsolar point direction was consistent with the result of the previous studies. The three-dimensional simulation results produced by varying the solar wind density and velocity were all included in the range of the Martian bow shock position observed by Mariner 4, Mars 2, 3, 5, and Phobos 2. Additionally, the simulation result also showed that the change of the solar wind density had a greater effect on the Martian bow shock position than the change of the solar wind velocity. Our result may be useful in analyzing the future observation data by Martian probes.

An Improved Validation Technique for the Temporal Discrepancy when Estimated Solar Surface Insolation Compare with Ground-based Pyranometer: MTSAT-1R Data use (표면도달일사량 검증 시 발생하는 시간 불일치 조정을 통한 정확한 일사량 검증: MTSAT-1R 자료 이용)

  • Yeom, Jong-Min;Han, Kyung-Soo;Lee, Chang-Suk;Kim, Do-Yong
    • Korean Journal of Remote Sensing
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    • v.24 no.6
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    • pp.605-612
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    • 2008
  • In this study, we estimate solar surface insolation (SSI) by using physical methods with MTSAT-1R data. SSI is regarded as crucial parameter when interpreting solar-earth energy system, climate change, and agricultural production predict application. Most of SSI estimation model mainly uses ground based-measurement such as pyranometer to tune the constructed model and to validate retrieved SSI data from optical channels. When compared estimated SSI with pyranometer measurements, there are some systemic differences between those instruments. The pyranometer data observed upward-looking hemispherical solid angle and distributed hourly measurements data which are averaged every 2 minute instantaneous observation. Whereas MTSAT-1R channels data are taken instantaneously images at fixed measurement time over scan area, and are pixel-based observation with a much smaller solid angle view. Those temporal discrepancies result from systemic differences can induce validation error. In this study, we adjust hour when estimate SSI to improve the retrieved accurate SSI.