• 천문학논총
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• 제30권2호
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• pp.47-51
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• 2015

Ground Level Enhancements (GLEs) in cosmic ray intensity observed during the period of 1997-2012 have been studied with energetic solar features and disturbances in solar wind plasma parameters and it is seen that all the GLEs have been found to be associated with coronal mass ejections, hard X-ray solar flares and solar radio bursts. All the GLEs have also been found to be associated with sudden jumps in solar proton flux of energy of ${\geq}60Mev$. A positive correlation with correlation coefficient of 0.48 has been found between the maximum percentage intensity (Imax%) of Ground Level Enhancements and the peak value of solar proton flux of energy (${\geq}60Mev$). All the Ground Level Enhancements have been found to be associated with jumps in solar wind plasma velocity (JSWV) events. A positive correlation with correlation coefficient of 0.43 has been found between the maximum percentage intensity (Imax %) of Ground Level Enhancements and the peak value of solar wind plasma velocity of associated (JSWV) events. All the Ground Level Enhancements have been found to be associated with jumps in solar wind plasma pressure (JSWP) events. A positive correlation with correlation coefficient of 0.67 has been found between the maximum percentage intensity (Imax %) of Ground Level Enhancements and the peak value of solar wind plasma pressure of associated (JSWP) events and of 0.68 between the maximum percentage intensity (Imax %) of Ground Level Enhancements and the magnitude of the jump in solar wind plasma pressure of associated (JSWP) events.

• 천문학회지
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• 제47권6호
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• pp.209-214
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• 2014

In this study we develop a set of solar proton event (SPE) forecast models with NOAA scales by Multi Layer Perceptron (MLP), one of neural network methods, using GOES solar X-ray flare data from 1976 to 2011. Our MLP models are the first attempt to forecast the SPE scales by the neural network method. The combinations of X-ray flare class, impulsive time, and location are used for input data. For this study we make a number of trials by changing the number of layers and nodes as well as combinations of the input data. To find the best model, we use the summation of F-scores weighted by SPE scales, where F-score is the harmonic mean of PODy (recall) and precision (positive predictive value), in order to minimize both misses and false alarms. We find that the MLP models are much better than the multiple linear regression model and one layer MLP model gives the best result.

• 천문학회보
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• 제35권2호
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• pp.45.2-45.2
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• 2010

We analyzed onset times of the largest six solar proton events during 1997-2006 of solar cycle 23, as observed at 1AU by two satellites of GOES/SEM (Geostationary Operational Environmental Satellites/the Space Environment Monitor) and SOHO/ERNE (Solar and Heliospheric Observatory/the Energetic and Relativistic Nuclei and Electron). We adopted the time shifted method suggested by Leon Kocharov and determined the path length by Sam Krucker's fitting method. We found some problems of those methods and tried to improve those. In this presentation, we will give details of the energy spectra of the 6 SPE events from the ERNE/HED, and onset time comparison among the SPE, flare, type II burst, and CME.

• 천문학회보
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• 제41권1호
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• pp.80.2-81
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• 2016

We investigate the dependence of solar proton events (SPEs) on solar and interplanetary type II bursts associated with solar flares and/or CME-driven shocks. For this we consider NOAA solar proton events from 1997 to 2012 and their associated flare, CME, and type II radio burst data with the following subgroups: metric, decameter-hectometric (DH), and meter-to-kilometric (m-to-km) type II bursts. The primary findings of this study are as follows. First, about half (52%) of the m-to-km type II bursts are associated with SPEs and its occurrence rate is higher than those of DH type II bursts (45%) and metric type II bursts (19%). Second, the SPE occurrence rate strongly depends on flare strength and source longitude, especially for X-class flare associated ones; it is the highest in the central region for metric (46%), DH (54%), and m-to-km (75%) subgroups. Third, the SPE occurrence rate is also dependent on CME linear speed and angular width. The highest rates are found in the m-to-km subgroup associated with CME speed 1500 kms-1: partial halo CME (67%) and halo CME (55%). Fourth, in the relationships between SPE peak fluxes and solar eruption parameters (CME linear speed, flare flux, and longitude), SPE peak flux is mostly dependent on SPE peak flux for all three type II bursts (metric, DH, m-to-km). It is noted that the dependence of SPE peak flux on flare peak flux decreases from metric to m-to-km type II burst.

• 천문학회보
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• 제36권2호
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• pp.90.1-90.1
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• 2011

We are developing empirical space weather (geomagnetic storms, solar proton events, and solar flares) forecast models based on solar information. These models have been set up with the concept of probabilistic forecast using historical events. Major findings can be summarized as follows. First, we present a concept of storm probability map depending on CME parameters (speed and location). Second, we suggested a new geoeffective CME parameter, earthward direction parameter, directly observable from coronagraph observations, and demonstrated its importance in terms of the forecast of geomagnetic storms. Third, the importance of solar magnetic field orientation for storm occurrence was examined. Fourth, the relationship among coronal hole-CIR-storm relationship has been investigated, Fifth, the CIR forecast based on coronal hole information is possible but the storm forecast is challenging. Sixth, a new solar proton event (flux, strength, and rise time) forecast method depending on flare parameters (flare strength, duration, and longitude) as well as CME parameter (speed, angular width, and longitude) has been suggested. Seventh, we are examining the rates and probability of solar flares depending on sunspot McIntosh classification and its area change (as a proxy of flux change). Our results show that flux emergence greatly enhances the flare probability, about two times for flare productive sunspot regions.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2010년도 한국우주과학회보 제19권1호
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• pp.38.3-39
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• 2010

While major solar proton events (SPEs) come from the coronal mass eject (CME)-driven shocks in solar wind, there are many evidences that potentiality of CMEs to generate SPEs depends on its early evolution near the Sun and on different solar activities observed around the CME liftoff time. To decipher origin of SPE release, we have investigated onset time comparison of the SPE with CME, metric type II radio burst, and hard X-ray flare. For this, we select 30 SPEs observed from 1997 to 2006 by using the particle instrument ERNE onboard SOHO, which allows proton flux anisotropy measurement in the energy range ~10 - 50MeV. Onset time of the SPEs is inferred by considering the energy-dependent proton transport time. As results, we found that (1) SPE onset time is comparable to that of type II but later than type III onset time and HXR start time, (2) SPE onset time is mostly later than the peak time of HXR flare, (3) almost half of the SPE onsets occurred after the HXR emission, and (4) there are two groups of CME height at the onset time of SPE; one is the height below 5 Rs (low corona) and the other is above 5Rs (high corona). In this talk, we will present the onset time comparison and discuss about the origin of the SPE onset.

• 한국태양에너지학회 논문집
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• 제34권4호
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• pp.9-16
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• 2014

A proton exchange membrane is a core component in the proton exchange membrane fuel cell because the role of proton exchange membrane(PEM)is supplying proton conductivity to fuel cell, a gas separator, and insulating between an anode and cathode. Among various role of PEM, supplying proton conductivity is the most important and the proton conductivity is strongly related the structural evolution of PEM by hydration. Thus a lot of studies have done by past few decade based on small angle X-ray scattering and wide angle X-ray scattering for understanding morphological structure of the PEM. Resulting from these studies, several morphological models of hydrated PEM are proposed. Current sensing atomic force microscopy (CSAFM) can map morphology and conductance on the membrane simultaneously. It can be the best tool for studying heterogenous structured materials such as PEM. In this study, the hydration of the membrane is examined by using CSAFM. Conductance and morphological images are simultaneously mapped under different relative humidity. The conductance images, which are mapped from different relative humidity, are analyzed by statistical methode for understanding ionic channel variation in PEM.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2011년도 한국우주과학회보 제20권1호
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• pp.28.4-29
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• 2011

Solar Proton Events (SPEs, ${\geq}\;10\;cm^{-1}s^{-1}sr^{-1}$ with >10 MeV) are very important for space weather forecasting. It is well known that they are associated with solar flares and/or CME-driven shocks. Especially, the CME-driven shocks have been observed as solar and interplanetary type II bursts. In this study, we estimated the occurrence probability of SPEs depending on three groups: (1) metric, (2) decameter-hectometric (D-H), and (3) meter-to-kilometric (m-to-km) type II bursts. For this work, we used SPEs and all available type II burst data in 1996-2004. The primary findings of this study are as follows. First, the majority (77%) of the m-to-km type II bursts are associated with SPEs and its probability is noticeably higher than D-H type II bursts probability strongly depend on longitude: eastern (0%), center(45%), and western (33%) for X-class associated metric type II bursts, eastern (15%), center (55%), and western (50%) for X-class associated D-H type II bursts, eastern (17%), center (77%), and western (64%) for X-class associated m-to-km type II bursts. Third, for m-to-km type II bursts, the SPE probability increases with CME speed: 400km/s${\leq}$V <1000km/s (36%), 1000km/s ${\leq}$V<1500km/s (40%), 1500km/s${\leq}$V (66%). Finally, we expect that these results will be used for setting up more reasonable solar proton event forecasting models.

• 열처리공학회지
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• 제32권1호
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• pp.29-35
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• 2019

The remedial junction is found in the network of single walled carbon nanotubes after the irradiation of protons not only for the better mechanical strength but also for the higher property of electrical conductivity. The irradiated proton formed a beam transferred sufficient energy to change the sp2 structure of atomic carbon as much as damage of crystalline formation, however it is shown the cross bonding while recovery of structure. This improved network in 2-D atomic chain of carbon is expected to use in a critical part in space energy harvesting system related with the solar radiation.

• 천문학회지
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• 제36권spc1호
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• pp.55-61
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• 2003

There are at least three effects of the non-thermal particle bombardment on the solar atmosphere: (1) non-thermal ionization and excitation; (2) proton-hydrogen charge exchange; (3) impact line polarization. Due to the non-thermal ionization and excitation effects of electron bombardments in flares, H$\alpha$ line is widely broadened and shows a strong central reversal. Significant enhancements at the line wings of Ly$\alpha$ and Ly$\beta$ are also predicted. In the case of proton bombardment, less strong broadening and no large central reversal are expected. However, due to proton-hydrogen charge exchange, the enhancements at the red wings of Ly$\alpha$ and especially of Ly$\beta$ lines at the early impulsive phase of flares are significant. Electron beam can also in some cases generates visible and UV continuum emission in white-light flares. However, at the onset phase, a negative 'black' flare may appear in several seconds, due to the increase of the $H^-$ opacity. The impact polarization of atomic lines can provide complementary information on the energetic particles, the energy transport and deposit in the solar chromosphere. New results of spectropolarimetric analysis for the major flare on July 23, 2002 are also given in the paper.