• Korean journal of applied entomology
• /
• v.16 no.3 s.32
• /
• pp.171-179
• /
• 1977

Since the outbreak of the brown planthopper (Nilaparvata lugens) in 1915 caused tremendous losses in rice production, one of the more effective method of prevention of such a disaster could be the establishment of longterm forecasting system, In 1916 the author indicated there was a correlation between sunspot activities and brown planthopper and the white back planthopper outbreaks. However, the examples seem to be too small size to state a definite correlation. The purpose of the present study IS to revi~w the history of the brown planthopper outbreaks, and to establish a more effective forcasting system. The present forcasting methods are based on light trap catches of adults which already migrate into this country from mainland China. The regular cycle of 11.2 years of sunspot activity began in 1710, and was continued to present. To gather more records of brown planthopper, the author checked 'Joseon Wangjo Silrok' and analized the so-called 'Hwang' 'Hwang-chung' and 'Chung' which have multiple meanings, together with 'Samguk Sagi' 'Goryo Sa' and 'Munheon Bigo.' The results obtained by the about from review of these old literature citations revealed that ten species of insect and unknown species were involved: i. e., pine moth (Dendrolimus spectabilis), army worm (Mythimna separata), brown planthopper (Nilarvata lugens), white-back planthopper (Sogatella furcifera), migratory locust (Locutsa migratoria), rice stem borer (Chilo suppressalis,), mole cricket (Gryllotalpa africana), rice-plant weevil (Echinocnemus squameus), cut worm (Euxoa segetum), and mulberry pyralid Margaronia pyloalis) The suspected incidence of planthopper in old records expressed by 'Hwang' or 'Chung' revealed a total or 25 out of 37 in 'Samguk sagi,' 21 out of 49 in 'Goryo sa,' 9 of 73 in 'Wanjo-silrog,' and none of 8 in 'Munheon bigo' were planthoppers. Therefore, a total of 36 out of 167 records of insect incidence in the old literature can be possibly attributed to planthoppers. The brown planthopper and white-back planthopper migrate together to Korea every year from mainland China, However, the number of each species are differ by year. In 1975 outbreak the brown planthopper was dominant; and the white-back planthopper prevailed in 1946 and 1977 outbreaks, During the course of this study, the author was able to add a new record of outbreak of planthop per. In 1916 the white-back planthopper outbreak caused serious losses in Chungcheong-namdo and Jeonla-namdo, with losses estimated as high as 160 and 190 thousand seok (23.2 and 27.5 thousand M/T), in Naju and Secheon county, respectively. Since 1912, major outbreaks of brown planthopper or white-back planthopper have been recored 5 times. These occurrences coincide and well matched the period of minimum number of sunspots, With these authenticated records of planthoppers, the author believes there is a close correlation between brown planthopper and white-back planthopper outbreaks in Korea and sunspot activities. Therefore, in years of low number of sunspots, we should watch for and expect outbreaks of these. insects. At this time, it will be necessary to provide all possible prevention measures.

• The Bulletin of The Korean Astronomical Society
• /
• v.40 no.1
• /
• pp.84.2-84.2
• /
• 2015

There are probabilistic forecast models for solar flare occurrence, which can be evaluated by various skill scores (e.g. accuracy, critical success index, heidek skill score, true skill score). Since these skill scores assume that two types of forecast errors (i.e. false alarm and miss) are equal or constant, which does not take into account different situations of users, they may be unrealistic. In this study, we make an evaluation of a probabilistic flare forecast model (Lee et al. 2012) which use sunspot groups and its area changes as a proxy of flux emergence. We calculate daily solar flare probabilities from 1996 to 2014 using this model. Overall frequencies are 61.08% (C), 22.83% (M), and 5.44% (X). The maximum probabilities computed by the model are 99.9% (C), 89.39% (M), and 25.45% (X), respectively. The skill scores are computed through contingency tables as a function of forecast probability, which corresponds to the maximum skill score depending on flare class and type of a skill score. For the critical success index widely used, the probability threshold values for contingency tables are 25% (C), 20% (M), and 4% (X). We use a value score with cost/loss ratio, relative importance between the two types of forecast errors. We find that the forecast model has an effective range of cost/loss ratio for each class flare: 0.15-0.83(C), 0.11-0.51(M), and 0.04-0.17(X), also depending on a lifetime of satellite. We expect that this study would provide a guideline to determine the probability threshold for space weather forecast.

• The Bulletin of The Korean Astronomical Society
• /
• v.38 no.2
• /
• pp.98-98
• /
• 2013

태양의 활동영역에서 관측할 수 있는 흑점은 주로 흑점군으로 관측되며, 태양폭발현상의 발생을 예보하기 위한 중요한 관측 대상 중 하나이다. 현재 태양 폭발을 예보하는 모델들은 McIntosh 흑점군 분류법을 사용하며 통계적 모델과 기계학습 모델로 나누어진다. 컴퓨터는 흑점군의 형태학적 특성을 연속적인 값으로 계산하지만 흑점군의 형태적 다양성으로 인해 McIntosh 분류법과 일치하지 않는 경우가 있다. 이러한 이유로 컴퓨터가 계산한 흑점군의 형태학적인 특성을 예보에 직접 적용하는 것이 필요하다. 우리는 흑점군을 검출하기 위해 최소신장트리(Minimum spanning tree : MST)를 이용한 계층적 군집화 기법을 수행하였다. 그래프(Graph)이론에서 최소신장트리는 정점(Vertex)과 간선(Edge)으로 구성된 간선의 가중치의 합이 최소인 트리이다. 우리는 모든 흑점을 정점, 그들의 연결을 간선으로 적용하여 최소신장트리를 작성하였다. 또한 최소신장트리를 활용한 계층적 군집화기법은 초기값에 따른 군집화 결과의 차이가 없기 때문에 흑점군 검출에 있어서 가장 적합한 알고리즘이다. 이를 통해 흑점군의 기본적인 형태학적인 특성(개수, 면적, 면적비 등)을 계산하고 최소신장트리를 통해 가장 면적이 큰 흑점을 중심으로 트리의 깊이(Depth)와 차수(Degree)를 계산하였다. 이 방법을 2003년 SOHO/MDI의 태양 가시광 영상에 적용하여 구한 흑점군의 내부 흑점수와 면적은 NOAA에서 산출한 값들과 각각 90%, 99%의 좋은 상관관계를 가졌다. 우리는 이 연구를 통해 흑점군의 형태학적인 특성과 더불어 예보에 직접적으로 활용할 수 있는 방법을 논의하고자 한다.

• Journal of Astronomy and Space Sciences
• /
• v.21 no.4
• /
• pp.315-328
• /
• 2004

In this paper, we present a good example of extreme solar and geomagnetic activities from October to November, 2003. These activities are characterized by very large sunspot groups, X-class solar flares, strong particle events, and huge geomagnetic storms. We discuss ground-based and space-based data in terms of space weather scales. Especially, we present several solar and geomagnetic disturbance data produced in Korea : sunspots, geo-magnetograms, aurora, Ionogram, and Total Electron Content (TEC) map by GPS data. Finally, we introduce some examples of the satellite orbit and communication effects caused by these activities; e.g., the disturbances of the KOMPSAT-1 operational orbit and HF communication.

• Journal of The Korean Astronomical Society
• /
• v.38 no.4
• /
• pp.463-470
• /
• 2005

In this paper, we have made the component-based development of observational software for KASI solar imaging spectrograph (KSIS) that is able to obtain three-dimensional imaging spectrograms by using a scanning mirror in front of the spectrograph slit. Since 2002, the KASI solar spectrograph has been successfully operated to observe solar spectra for a given slit region as well as to inspect the response functions of narrow band filters. To improve its capability, we have developed the KSIS that can perform sequential observations of solar spectra by simultaneously controlling the scanning mirror and the CCD camera via Visual C++. Main task of this paper is to introduce the development of the component-based software for KSIS. Each component of the software is reusable on the level of executable file instead of source code because the software was developed by using CBD (component-based development) methodology. The main advantage of such a component-based software is that key components such as image processing component and display component can be applied to other similar observational software without any modifications. Using this software, we have successfully obtained solar imaging spectra of an active region (AR 10708) including a small sunspot. Finally, we present solar $H{\alpha}$ spectra ($6562.81{\AA}$) that were obtained at an active region and a quiet region in order to confirm the validity of the developed KSIS and its software.

• The Bulletin of The Korean Astronomical Society
• /
• v.38 no.1
• /
• pp.65.1-65.1
• /
• 2013

The 2011 August 09 Flare is one of the largest X-ray flares of Sunspot Cycle 24 to attract a lot of attention for its various activities detected in coronal images. In this study we concern ourselves mostly on information of high energy electrons produced during this flare provided by hard X ray data from the Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) and radio data from the Korean Solar Radio Burst Locator (KSRBL) and Ondrejov. EUV images obtained by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory are used to provide the context of magnetic reconnection. In our results, (1) HXR spectra have a rich spectral morphology. Initially it could be fit by one thermal component (T~30MK) and one single power law nonthermal spectrum, but later a better fit could be made by introducing an additional thermal component (T~55 MK). (2) Time delays between the KSRBL burst and the RHESSI hard X-ray emission were found which are more obvious at low frequencies and insignificant at high frequencies. (3) The HXR source lies in the core of the quadrupolar active region. In our interpretation based on AIA 94 A images, the outer part of the active region erupted to be blown out, leaving the intense hard X-ray emission concentrated in the core. We relate the appearance of the second thermal component to the evolution of the AIA 171 and 94 A images. The time delays of microwave peaks to HXR peaks are interpreted as indicating presence of trapped electrons in larger closed magnetic loops. With these result we conclude that the hard X ray and microwaves are due to impulsive acceleration in the low and high heights and a sigmoidal reconnection scenario.

• The Bulletin of The Korean Astronomical Society
• /
• v.41 no.1
• /
• pp.31.4-32
• /
• 2016

Observing the solar atmosphere with ground-based telescopes in the near-infrared has a number of advantages when compared to classical measurements in visible wavelengths. One of them comes from the magnetic sensitivity of spectral lines, which varies as ${\lambda}_g$, where g is the effective $Land{\acute{e}}$ factor of the transition. This wavelength dependence makes the near-infrared range adequate to study subtle spatial or temporal variations of the magnetic field. Spectral lines, such as the photospheric Fe I $1.5648{\mu}m$ spectral line, with a $Land{\acute{e}}$ factor g=3, have often been used in the past for this type of studies. To study the chromosphere, the Ca II IR triplet and the He I $1.0830{\mu}m$ triplet are the most often observed lines. The latter has the additional advantage that the photospheric Si I $1.0827{\mu}m$ is close enough so that photosphere and chromosphere can be simultaneously recorded with a single detector in a spectrograph. The instrument TIP (Tenerife Infrared Polarimeter) has been continuously operating since 1999 at the 70-cm German VTT of the Observatorio del Teide and has been recently moved to the 1.5-m German GREGOR. During all this time, results have been obtained concerning the nature of the weak photospheric magnetic field of the quiet sun, magneto-acoustic wave propagation, evolution with the cycle of sunspot magnetic fields, photospheric and chromospheric magnetic field in emerging regions, magnetic field in chromospheric structures such as filaments, prominences, flares, and spicules, etc. In this talk, I will review the main results obtained after all these observations and mention the main challenges for the future. With its novel polarization-free design and a complete suite of instruments aimed at simultaneous (imaging and spectroscopic) observations of the solar photosphere and chromosphere, the EST (European Solar Telescope) will represent a major world-wide infrastructure to understand the physical nature of all these phenomena.

• The Bulletin of The Korean Astronomical Society
• /
• v.41 no.1
• /
• pp.80.1-80.1
• /
• 2016

There are probabilistic forecast models for solar flare occurrence, which can be evaluated by various skill scores (e.g. accuracy, critical success index, heidek skill score, and true skill score). Since these skill scores assume that two types of forecast errors (i.e. false alarm and miss) are equal or constant, which does not take into account different situations of users, they may be unrealistic. In this study, we make an evaluation of a probabilistic flare forecast model [Lee et al., 2012] which use sunspot groups and its area changes as a proxy of flux emergence. We calculate daily solar flare probabilities from 2011 to 2014 using this model. The skill scores are computed through contingency tables as a function of forecast probability, which corresponds to the maximum skill score depending on flare class and type of a skill score. We use a value score with cost/loss ratio, relative importance between the two types of forecast errors. The forecast probability (y) is linearly changed with the cost/loss ratio (x) in the form of y=ax+b: a=0.88; b=0 (C), a=1.2; b=-0.05(M), a=1.29; b=-0.02(X). We find that the forecast model has an effective range of cost/loss ratio for each class flare: 0.536-0.853(C), 0.147-0.334(M), and 0.023-0.072(X). We expect that this study would provide a guideline to determine the probability threshold and the cost/loss ratio for space weather forecast.

• The Journal of the Convergence on Culture Technology
• /
• v.6 no.1
• /
• pp.255-261
• /
• 2020

Versatile and innovative interdisciplinary professionals refer to those who can engage in an efficient cooperation with experts in other fields or to those who can themselves put knowledge of different fields together. This article aims to look into Galileo Galilei as an example of historic figure that made remarkable achievements by merging knowledge in multiple fields of study. It also shows that Galileo, who had active exchange with painters during the Renaissance, presented the findings from his telescope observations in the form of drawings and that he used them to build core logics that criticizes the traditional Aristotelian cosmology. Galileo drew the critical logics, hardly achievable from a simple observation report or mathematical demonstration, from his hand drawing. The Galileo case well proposes the goals and direction of how the modern society should nurture its interdisciplinary professionals today.

• Journal of The Korean Astronomical Society
• /
• v.24 no.2
• /
• pp.129-149
• /
• 1991

An attempt has been made to examine the characteristics of acoustic and MHD waves generated in stellar convection zones($4000\;K\;{\leq}\;T_{eff}\;{\leq}\;7000\;K$, $3\;{\leq}\;\log\;g\;{\leq}\;4.5$). With the use of wave generation theories formulated for acoustic waves by Stein (1967), for MHD body waves by Musielak and Rosner (1987, 1988) and for MHD tube waves by Musielak et al.(l989a, 1989b), the energy fluxes are calculated and their dependence on effective temperature, surface gravity and megnetic field strength are analyzed by optimization techniques. In computing magneto-convection models, the effect of magnetic fields on the efficiency of convection has been taking into account by extrapolating it from Yun's sunspot models(1968; 1970). Our study shows that acoustic wave fluxes are dominant in F and G stars, while the MHD waves dominant in K and M stars, and that the MHD wave fluxes vary as $T_{eff}^4{\sim}T_{eff}^7$ in contrast to the acoustic fluxes, as $T_{eff}^{10}$. The gravity dependence, on the other hand, is found to be relatively weak; the acoustic wave fluxes ${\varpropto}\;g^{-0.5}$, the longitudinal tube wave fluxes ${\varpropto}\;g^{0.3}$ and the transverse tube wave fluxes ${\varpropto}\;g^{0.3}$. In the case of the MHD body waves their gravity dependence is found to be nearly negligible. Finally we assesed the computed energy fluxes by comparing them with the observed fluxes $F_{ob}$ of CIV(${\lambda}1549$) lines and soft X-rays for selected main sequence stars. When we scaled the corrected wave fluxes down to $F_{ob}$, it is found that these slopes are almost in line with each other.