• Bulletin of the Korean Space Science Society
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• 2008.04a
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• pp.22.4-23
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• 2008

• The Bulletin of The Korean Astronomical Society
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• v.34 no.2
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• pp.28.1-28.1
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• 2009

• International Journal of Aeronautical and Space Sciences
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• v.18 no.1
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• pp.138-143
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• 2017

A performance analysis for a pulsed plasma thruster(PPT) has been conducted to predict the thrust and current change. Two models were implemented - a one-dimensional lumped circuit analysis model and the Teflon ablation model provided by Michael Keidar. The circuit model incorporating resistance and inductance models was adapted to predict the magnitude of the discharge current. Numerical simulations like current discharge rates with different voltages were reasonably well compared with experimental data. The effects of Teflon ablation on thruster characteristics were investigated.

• Journal of Korea Multimedia Society
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• v.19 no.1
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• pp.80-85
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• 2016

It costs high in both memory usage and time consuming to sample the space to compute charge density and calculate electric field on that with large size of plasma data. In real-time and interactive application, accelerating the compute time is critical problem. In this paper, we suggest new method to visualize electric field by using convolution theorem, and the parallel computing to accelerate computing time by using GPGPU. We conduct a simulation that compare running time between the methods with convolution and without convolution. We discussed the method of visualization of multivariate data in three dimensional space using colored volume rendering and surface construction.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.167-170
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• 2005

The mechanism of striation in the coplanar- and matrix-type plasma display panel (PDP) cells has been studied using the particle-in-cell Monte-Carlo Collision (PIC-MCC) model. The striation formation is related to the ionization energy of neutral atoms and the well-like deformation of space potential by space charge distribution. Negative wall charge accumulation by electrons on the MgO surface of the anode region is also one of the key factors for the formation of striation. The clearness of the striation phenomenon in PIC-MCC code in comparison with fluid code can be explained by using nonlocal electron kinetic effect.

• Journal of Astronomy and Space Sciences
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• v.31 no.1
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• pp.73-81
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• 2014

A package of space science instruments, dubbed the Instruments for the Study of Space Storms (ISSS), is proposed for the Next Generation Small Satellite-1 (NEXTSat-1), which is scheduled for launch in May 2016. This paper describes the instrument designs and science missions of the ISSS. The ISSS configuration in NEXTSat-1 is as follows: the space radiation monitoring instruments consist of medium energy particle detector (MEPD) and high energy particle detector (HEPD); the space plasma instruments consist of a Langmuir probe (LP), a retarding potential analyzer (RPA), and an ion drift meter (IDM). The space radiation monitoring instruments (MEPD and HEPD) measure electrons and protons in parallel and perpendicular directions to the geomagnetic field in the sub-auroral region, and they have a minimum time resolution of 50 msec for locating the region of the particle interactions with whistler mode waves and electromagnetic ion cyclotron (EMIC) waves. The MEPD measures electrons and protons with energies of tens of keV to ~400 keV, and the HEPD measures electrons with energies of ~100 keV to > ~1 MeV and protons with energies of ~10 MeV. The space plasma instruments (LP, RPA, and IDM) observe irregularities in the low altitude ionosphere, and the results will be compared with the scintillations of the GPS signals. In particular, the LP is designed to have a sampling rate of 50 Hz in order to detect these small-scale irregularities.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.88.1-88.1
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• 2013

We have investigated vertical motions of plasma in the pores and changes of the motions with height by using high time and spatial resolutions data obtained by the Fast Imaging Solar Spectrograph (FISS) of the 1.6 meter New Solar Telescope (NST). We infer the LOS velocity by applying the bisector method to the wings of CaII 854.2 nm line profile. We find that (1) upflow velocity in the pores decreases with height and turns into downward in the upper chromosphere; (2) 3 min and 5 min oscillations are found from the Doppler velocity in the pore at various wavelengths from the wing (${\pm}2.35{\AA}$) to the core (${\pm}1.25{\AA}$) of the CaII line; and (3) power of high (low) frequency oscillation obtained from the CaII intensity increases (decreases) with height. We discuss the physical implications of our results in view of the connection of LOS plasma flows in a concentrated magnetic flux (pore) between the photosphere and the low chromosphere.

• Bulletin of the Korean Space Science Society
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• 2006.10a
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• pp.52-52
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• 2006

Many spacecraft failures and anomalies have been attributed to energetic electrons in the Earth's magnetosphere. While the dynamics of these electrons have been studied extensively for several decades, the fundamental question of how they are accelerated is not fully resolved. Proposed theories have not been successful in explaining fast high energy increase such as REE (Relativistic electron enhancement). In this presentation, we show observations of energetic electron precipitation measured by the Korean satellite, STSAT-1 which simultaneously detect (100ev - 20 keV) and (170 - 360 keV) energy electrons at the 680 km orbit, when the RES event observed at the geosynchronous orbit on October 13, 2004. STSAT-1 observed intense electron precipitation in both energy ranges occurred in the midnight sector clearly demonstrating that electrons having wide energy band are injected from the plasma sheet. To make the balance between loss and injection, the injected electron flux should be also large. In this situation, the injected electrons can be trapped into the magnetosphere and produce REE, though they have low e-folding energies. We propose this plasma sheet injection might be the primary source of relativistic electron (1 MeV) flux increases.

• Journal of The Korean Astronomical Society
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• v.56 no.2
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• pp.225-229
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• 2023

We investigated an emerging magnetic loop dynamically formed on the Sun, which has the effective footpoint heating source that may play a key role in heating a solar atmosphere with free magnetic energy in it. It is suggested that the heating source could be related to local compression of a plasma in the emerging loop by means of Lorentz force, which converts the magnetic energy to the internal energy of the plasma that is used to reaccelerate a decelerated downflow along the loop, eventually generating the source when the kinetic energy of the downflow is thermalized. By analyzing very high-cadense data obtained from a magnetohydrodynamic simulation, we demonstrate how the local compression is activated to trigger the generation of the heating source. This reveals a characteristic of the emerging loop that experiences a dynamic loop-loop interaction, which causes the local compression and makes the plasma gain the internal energy converted from the magnetic energy in the atmosphere. What determines the characteristic that could distinguish an illuminated emerging loop from a nonilluminated one is discussed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.2
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• pp.90-97
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• 2019

Sparkjet actuator, also known as plasma synthetic jet actuator (PSJA), is an active flow control device that has possibility of controling supersonic flow. This actuator utilizes arc plasma to deposit energy onto the gas inside the cavity to raise temperature and pressure. A change in the state of the fluid inside the cavity generates pressure waves and momentum jet, and they are exhausted through out the orifice exit and disturb external flow field. Since the cavity flow is affected by arc plasma, which is an equilibrium plasma and have generated equilibrium flow, the equilibrium state of air should be considered in order to analyze the flow of sparkjet actuator. In this study, numerical program for equilibrium flow was developed for the use of sparkjet actuator analysis. The developed program was validated by comparing the time - accurate jet front positions with the reference result. Then, impulse characteristics of the actuator in the atmospheric quiescent air were explained.