• Title/Summary/Keyword: Solar Astronomy

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Development of DIagnostic Coronagraph Experiment (DICE) for Total Solar Eclipse

  • Choi, Seonghwan;Kim, Jihun;Park, Jongyeob;Jang, Biho;Bong, Suchan;Cho, Kyung-Suk
    • The Bulletin of The Korean Astronomical Society
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    • v.42 no.2
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    • pp.66.3-66.3
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    • 2017
  • Korea Astronomy and Space Science Institute (KASI) is developing a coronagraph in collaboration with National Aeronautics and Space Administration (NASA) which will be installed on the International Space Station (ISS). The coronagraph can measure speed and temperature by using four filters approximately 400 nm and polarization filter in three different angles, differently with older coronagraphs. For the successful mission, it has development and experiment progress in three phases; total solar eclipse experiment in 2017, balloon experiment in 2019, and the ISS installation in 2021. As a first experiment, we developed a coronagraph without an occulter named with Diagnostic Coronagraph Experiment (DICE) for experiment for filter system and imaging sensor. We designed optics with a field of view from 2.5 to 15 solar radii. It has four filters approximately 400 nm and polarizer to measure speed and velocity of the solar corona. For the selection of filter or polarization angle, it has two mechanism parts; filter wheel assembly and a polarizer wheel assembly. Especially we used Core Flight System (CFS) platform which was developed by NASA, when we develop the coronagraph operation software. It provides us stability, reusability, and compatibility.

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Science Goal of the Diagnostic Coronagraph on the International Space Station

  • Bong, Su-Chan;Kim, Yeon-Han;Cho, Kyung-Suk;Lee, Jae-Ok;Seough, Jungjoon;Park, Young-Deuk;Newmark, Jeffrey S.;Gopalswamy, Natchimuthuk;Viall, Nicholeen M.;Antiochos, Spiro;Arge, Charles N.;Yashiro, Seiji;Reginald, Nelson L.;Fineschi, Silvano;Strachan, Leonard
    • The Bulletin of The Korean Astronomical Society
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    • v.43 no.2
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    • pp.47.3-47.3
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    • 2018
  • The Korea Astronomy and Space Science Institute (KASI) plans to develop a coronagraph in collaboration with the National Aeronautics and Space Administration (NASA), to be installed on the International Space Station (ISS). It uses multiple filters to obtain simultaneous measurements of electron density, temperature, and velocity within a single instrument. The primary science goal is to understand the physical conditions in the solar wind acceleration region, and the secondary goal is to enable and validate the next generation of space weather science models. The planned launch in 2022 provides great potential for synergy with other solar space missions such as Solar Orbiter and Parker Solar Probe.

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Construction of Korean Space Weather Prediction Center: Space radiation effect

  • Lee, Jae-Jin;Cho, Kyung-Suk;Hwang, Jung-A;Kwak, Young-Sil;Kim, Khan-Hyuk;Bong, Su-Chan;Kim, Yeon-Han;Park, Young-Deuk;Choi, Seong-Hwan
    • Bulletin of the Korean Space Science Society
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    • 2008.10a
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    • pp.33.3-34
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    • 2008
  • As an activity of building Korean Space Weather Prediction Center (KSWPC), we has studied of radiation effect on the spacecraft components. High energy charged particles trapped by geomagnetic field in the region named Van Allen Belt can move to low altitude along magnetic field and threaten even low altitude spacecraft. Space Radiation can cause equipment failures and on occasions can even destroy operations of satellites in orbit. Sun sensors aboard Science and Technology Satellite (STSAT-1) was designed to detect sun light with silicon solar cells which performance was degraded during satellite operation. In this study, we try to identify which particle contribute to the solar cell degradation with ground based radiation facilities. We measured the short circuit current after bombarding electrons and protons on the solar cells same as STSAT-1 sun sensors. Also we estimated particle flux on the STSAT-1 orbit with analyzing NOAA POES particle data. Our result clearly shows STSAT-1 solar cell degradation was caused by energetic protons which energy is about 700 keV to 1.5 MeV. Our result can be applied to estimate solar cell conditions of other satellites.

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DEVELOPMENT OF 2.8-GHZ SOLAR FLUX RECEIVERS

  • Yun, Youngjoo;Park, Yong-Sun;Kim, Chang-Hee;Lee, Bangwon;Kim, Jung-Hoon;Yoo, Saeho;Lee, Chul-Hwan;Han, Jinwook;Kim, Young Yun
    • Journal of The Korean Astronomical Society
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    • v.47 no.6
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    • pp.201-207
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    • 2014
  • We report the development of solar flux receivers operating at 2.8 GHz to monitor solar radio activity. Radio waves from the sun are amplified, filtered, and then transmitted to a power meter sensor without frequency down-conversion. To measure solar flux, a calibration scheme is designed with a noise source, an ambient load, and a hot load at $100^{\circ}C$. The receiver is attached to a 1.8 m parabolic antenna in Icheon, owned by National Radio Research Agency, and observation is being conducted during day time on a daily basis. We compare the solar fluxes measured for last seven months with solar fluxes obtained by DRAO in Penticton, Canada, and by the Hiraiso solar observatory in Japan, and finally establish equations to convert observed flux to the so-called Penticton flux with an accuracy better than 3.2 sfu.

Do Solar Cycles Share Spectral Properties with Tropical Cyclones that Occur in the Western North Pacific Ocean?

  • Kim, Ki-Beom;Kim, Jung-Hee;Chang, Heon-Young
    • Journal of Astronomy and Space Sciences
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    • v.35 no.3
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    • pp.151-161
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    • 2018
  • Understanding solar influences on extreme weather is important. Insight into the causes of extreme weather events, including the solar-terrestrial connection, would allow better preparation for these events and help minimize the damage caused by disasters that threaten the human population. In this study, we examined category three, four, and five tropical cyclones that occurred in the western North Pacific Ocean from 1977 to 2016. We compared long-term trends in the positions of tropical cyclone occurrence and development with variations of the observed sunspot area, the solar North-South asymmetry, and the southern oscillation index (SOI). We found that tropical cyclones formed, had their maximum intensity, and terminated more northward in latitude and more westward in longitude over the period analyzed; they also became stronger during that period. It was found that tropical cyclones cannot be correlated or anti-correlated with the solar cycle. No evidence showing that properties (including positions of occurrence/development and other characteristics) of tropical cyclones are modulated by solar activity was found, at least not in terms of a spectral analysis using the wavelet transform method.

Association between Solar Variability and Teleconnection Index

  • Kim, Jung-Hee;Chang, Heon-Young
    • Journal of Astronomy and Space Sciences
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    • v.36 no.3
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    • pp.149-157
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    • 2019
  • In this study, we investigate the associations between the solar variability and teleconnection indices, which influence atmospheric circulation and subsequently, the spatial distribution of the global pressure system. A study of the link between the Sun and a large-scale mode of climate variability, which may indirectly affect the Earth's climate and weather, is crucial because the feedbacks of solar variability to an autogenic or internal process should be considered with due care. We have calculated the normalized cross-correlations of the total sunspot area, the total sunspot number, and the solar North-South asymmetry with teleconnection indices. We have found that the Southern Oscillation Index (SOI) index is anti-correlated with both solar activity and the solar North-South asymmetry, with a ~3-year lag. This finding not only agrees with the fact that El $Ni{\tilde{n}}o$ episodes are likely to occur around the solar maximum, but also explains why tropical cyclones occurring in the solar maximum periods and in El $Ni{\tilde{n}}o$ periods appear similar. Conversely, other teleconnection indices, such as the Arctic Oscillation (AO) index, the Antarctic Oscillation (AAO) index, and the Pacific-North American (PNA) index, are weakly or only slightly correlated with solar activity, which emphasizes that response of terrestrial climate and weather to solar variability are local in space. It is also found that correlations between teleconnection indices and solar activity are as good as correlations resulting from the teleconnection indices themselves.

Competition between ICME and crustal magnetic field on the loss of Mars atmosphere

  • Hwang, Junga;Jo, Gyeongbok;Kim, Roksoon;Jang, Soojeong;Cho, Kyungsuk;Lee, Jaejin;Yi, Yu
    • The Bulletin of The Korean Astronomical Society
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    • v.42 no.2
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    • pp.62.3-63
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    • 2017
  • The Mars Atmosphere and Volatile (MAVEN) mission has been providing valuable information on the atmospheric loss of Mars since its launch in November 2013. The Neutral Gass and Ion Mass Spectrometer (NGIMS) onboard MAVEN, was developed to analyze the composition of the Martian upper atmospheric neutrals and ions depending on various space weather conditions. We investigate a variation of upper atmospheric ion densities depending on the interplanetary coronal mass ejections (ICMEs). It is known that the Mars has a very weak global magnetic field, so upper atmosphere of Mars has been strongly affected by the solar activities. Meanwhile, a strong crustal magnetic field exists on local surfaces, so they also have a compensating effect on the upper atmospheric loss outside the Mars. The weak crustal field has an influence up to 200km altitude, but on a strong field region, especially east longitude of $180^{\circ}$ and latitude of $-50^{\circ}$, they have an influence over 1,400km altitude. In this paper, we investigated which is more dominant between the crustal field effect and the ICME effect to the atmospheric loss. At 400km altitude, the ion density over the strong crustal field region did not show a significant variation despite of ICME event. However, over the other areas, the variation associated with ICME event is far more overwhelming.

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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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Construction of Korean Space Weather rediction Center: K-SRBL

  • Bong, Su-Chan;Kim, Yeon-Han;Cho, Kyung-Suk;Choi, Seong-Hwan;Park, Young-Deuk;Gary, Dale E.
    • Bulletin of the Korean Space Science Society
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    • 2008.10a
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    • pp.32.2-32.2
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    • 2008
  • A major solar radio burst can disturb many kinds of radio instruments, including cellular phone, GPS, and radar. Korea Astronomy and Space Science Institute (KASI) is developing Korean Solar Radio Burst Locator (KSRBL) in collaboration with New Jersey Institute of Technology. KSRBL is a single dish radio spectrograph, which records the spectra of microwave (0.5 - 18 GHz) bursts with 1 MHz spectral resolution and 1 s time cadence, and locates their positions on the solar disk within 2 arcmin. Hardware manufacturing is almost completed including 4-channel digitizer/FPGA. The system is currently installed at Owens Valley Radio Observatory (OVRO), and test of the operation is in progress. It will be installed at KASI in 2009. We report current status and test results of KSRBL.

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On the Relation Between the Sun and Climate Change with the Solar North-South Asymmetry (태양의 북-남 비대칭성을 고려한 태양활동과 기후변화와의 관계)

  • Cho, I.H.;Kwak, Y.S.;Cho, K.S.;Choi, H.S.;Chang, H.Y.
    • Journal of Astronomy and Space Sciences
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    • v.26 no.1
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    • pp.25-30
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    • 2009
  • We report the relation between the solar activity and terrestrial climate change with the solar north-south asymmetry. For this purpose, we calculate sliding correlation coefficients between sunspot numbers and earth's mean annual temperature anomalies. Then, we compare the epoch that the sign of correlation changes with the epoch that the sign of the solar north-south asymmetry changes. We obtain that corresponding times are 1907 and 1985, respectively. Further more, these two epoches are well consistent with those of signs of the solar north-south asymmetry changes. We also obtain that the plot between sunspot numbers and temperature anomalies could be classified by 1907 and 1985. We conclude that temperature anomalies are shown to be negatively correlated with sunspot numbers when the southern solar hemisphere is more active: and vice versa.