• Journal of Astronomy and Space Sciences
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• 제20권1호
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• pp.53-62
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• 2003

SPS(Space Physics Sensor)는 1999년 발사된 다목적 실용 위성 1호(KOMPSAT-I)에 실린 관측 장비로서, 태양 활동 극대기인 2000년 6월부터 2001년 8월까지 지구 이온층에 관한 자료를 지구로 전송하였다. 이 자료 중 때때로 저위도 지역에서 급격한 플라즈마 밀도 증가 현상을 볼 수 있었다. 이러한 현상의 통계적 분포를 살펴본 결과, 지구 자기장이 약한 대서양 지역과 하와이 지역에서 발생 확률이 가장 높으며, 지자기 활동성 지수인 Dst나 태양 활동성을 나타내는 F10.7지수와는 특별한 상관관계가 없다는 사실을 확인할 수 있었다. 밀도 증가 지역 내의 전자 온도 변화는 개별 사건마다 증가, 유지, 또는 감소를 보이고 있으나, 온도가 급격히 감소하는 경우가 지배적이었다.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2009년도 한국우주과학회보 제18권2호
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• pp.38.3-39
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• 2009

Equatorial Plasma Bubble (herafter, EPB) is a common feature in low-latitude F-region during the night time. Since EPB causes significant impacts on the satellite communication and navigation systems, its accurate forecast is highly demanded by the GNSS users. Thus, further understanding of these features and their configuration is a challenging issue in space weather studies. The day-to-day variability of the plasma bubble activity was investigated by analyzing the TIMED/GUVI, ROCSAT-1, DMSP, and CHAMP satellite data. The pre-reversal enhancement (PRE) is known as the most important single parameter for the onset of plasma bubbles but we do not know yet to what extent the day-to-day variability of the bubble activity can be attributed to the PRE. We obtained the magnitude of the PRE from ROCSAT-1 and the occurrence of bubbles in relation to the PRE was investigated by using the coincident observations of EPBs from TIMED/GUVI, DMSP, and CHAMP. By conducting one-to-one comparison of the PRE characteristics with the EPB occurrence we examined the role of the PRE in the onset of EPBs.

• 우주기술과 응용
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• 제2권2호
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• pp.104-120
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• 2022

도요샛(Small Scale magNetospheric and Ionospheric Plasma Experiment, SNIPE)의 과학임무는 전리권 상층부 소규모 플라즈마 구조의 공간적 시간적 변화를 관찰하는 것이다. 이를 위해 4개의 6U 큐브위성(10 kg)이 고도 약 500 km 극궤도로 발사될 예정이며, 상호 위성 간 거리는 편대 비행 알고리즘에 의해 수 10 km에서 수 1,000 km 이상으로 제어된다. 운영 초기에는 4기의 위성이 같은 궤도 평면에 위치하는 종대비행을 하다가 경도상에서 나란히 배치되는 횡대비행으로 전환하여 4기의 서로 다른 지점에서 공간적인 변화를 관측하게 된다. 도요샛에는 입자 검출기, 랑뮈어 탐침, 자력계로 구성된 우주날씨 관측 장비가 각 위성에 탑재된다. 모든 관측기는 10 Hz 이상의 높은 시간 분해능을 가지며 큐브위성에 최적화 설계되었다. 이 외에도 이리디듐 통신 모듈은 지자기 폭풍이 발생할 때 작동 모드를 변경하기 위한 명령을 업로드할 수 있는 기회를 제공한다. 도요샛은 극 지역 플라즈마 밀도 급상승, 필드 정렬 전류, 고에너지 전자의 국소 영역 침투, 적도 및 중위도 플라즈마 거품의 발생 및 시공간적 진화에 대한 관찰을 수행할 예정이며, 이를 통해 태양풍이 우주날씨에 어떠한 영향을 미치는지 탐구하게 된다. 도요샛은 2023년 상반기 러시아 소유즈-2에 의해 카자흐스탄 바이코누르에서 발사될 예정이다.

• Journal of Astronomy and Space Sciences
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• 제5권1호
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• pp.1-8
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• 1988

Electron beam propagation in a fully ionized plasma has been studied using a one-dimensional particle simulation model. We compare the results of electrostatic simulations to those of electromagnetic simulations. The electrostatic results show the essential features of beam-plasma interactions. It is found that the return currents are enhanced by the beam-plasma instability which accelerates ambinet plasmas. The results also show the heating of ambient plasmas and the trapping of plasmas due to the locally generated electric field. The electromagnetic simulations show much the same results as the electrostatic simulations do. The level of the radiation generated by the same non-relativistic beam is slightly higher than the noise level. We discuss the results in context in context of the heating of coronal plasma during solar flares.

• Journal of Astronomy and Space Sciences
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• 제32권1호
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• pp.13-19
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• 2015

Plasma bubbles that occur in the equatorial F-region make up one of the most distinguishing phenomena in the ionosphere. Bubbles represent plasma depletions with respect to the background ionosphere, and are the major source of electron density irregularities in the equatorial F-region. Such bubbles are seen as plasma depletion holes (in situ satellite observations), vertical plumes (radar observations), and emission-depletion bands elongated in the north-south direction (optical observations). However, no technique can observe the whole three-dimensional structure of a bubble. Various aspects of bubbles identified using different techniques indicate that a bubble has a "shell" structure. This paper reviews the development of the concepts of "bubble" and "shell" in this context.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.842-848
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• 2008

In this study, we propose a novel micro-ion engine system. Single plasma source is used for both ion beam source and neutralizing electron source. By changing the electrical connection, either operation can be switched. This micro-ion engine system gives translation motion and attitude control to microspacecraft. The major objective of this study is verification of our concept. Small plasma source of 20 mm diameter was developed. Plasma was sustained by microwave power. Using this plasma source, ion beam extraction and electron emission was successively demonstrated.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2009년도 한국우주과학회보 제18권2호
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• pp.23.1-23.1
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• 2009

Space physics is more than fifty years old and is going through middle age. Looking back and thinking about what has been learned during the past fifty years, one finds that progress was made at the expense of exactness. Past observations have been interpreted using theory with unreal assumptions. Theory and models must be testable, verifiable and consistent with observations. Current theory cannot explain many important observational results that are relevant for understanding how space plasmas work. This talk will examine the current model of space plasma and assess its capabilities. We will then discuss the required level of theory and models that should be developed to advance space physics to the next tier.

• Journal of Astronomy and Space Sciences
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• 제21권3호
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• pp.201-208
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• 2004

In this paper we have examined the effect of dust charge density on nonlinear ion acoustic solitary wave which propagates obliquely with respect to the external magnetic field in a dusty plasma. For the dusty charge density below a critical value, the Sagdeev potential $\Psi1(n)$ has a singular point in the region n < 1, where n is the ion number density divided by its equilibrium number density. If there exists a dust charge density over the critical value, the Sagdeev potential becomes a finite function in the region n < 1, which means that there may exist the rarefactive ion acoustic solitary wave. By expanding the Sagdeev potential in the small amplitude limit up to on4 near n=1, we find the solution of ion acoustic solitary wave. Therefore we suggest that the dust charge density plays an important role in generating the rarefactive solitary wave.

• Journal of Astronomy and Space Sciences
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• 제39권3호
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• pp.117-126
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• 2022

The Ionospheric Anomaly Monitoring by Magnetometer And Plasma-probe (IAMMAP) is one of the scientific instruments for the Compact Advanced Satellite 500-3 (CAS 500-3) which is planned to be launched by Korean Space Launch Vehicle in 2024. The main scientific objective of IAMMAP is to understand the complicated correlation between the equatorial electro-jet (EEJ) and the equatorial ionization anomaly (EIA) which play important roles in the dynamics of the ionospheric plasma in the dayside equator region. IAMMAP consists of an impedance probe (IP) for precise plasma measurement and magnetometers for EEJ current estimation. The designated sun-synchronous orbit along the quasi-meridional plane makes the instrument suitable for studying the EIA and EEJ. The newly-devised IP is expected to obtain the electron density of the ionosphere with unprecedented precision by measuring the upper-hybrid frequency (f_UHR) of the ionospheric plasma, which is not affected by the satellite geometry, the spacecraft potential, or contamination unlike conventional Langmuir probes. A set of temperature-tolerant precision fluxgate magnetometers, called Adaptive In-phase MAGnetometer, is employed also for studying the complicated current system in the ionosphere and magnetosphere, which is particularly related with the EEJ caused by the potential difference along the zonal direction.

• 천문학회보
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• 제40권1호
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• pp.66.3-67
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• 2015

Without scrutinizing reflection, the plasma comprising a coronal loop is usually regarded to reside within a flux rope. This picture seems to have been adopted from laboratory plasma pinches, in which a plasma of high density and pressure is confined in the vicinity of the flux rope axis by magnetic tension and magnetic pressure of the concave inward magnetic field. Such a configuration, in which the plasma pressure gradient and the field line curvature vector are almost parallel, however, is known to be vulnerable to ballooning instabilities (to which belong interchange instabilities as a subset). In coronal loops, however, ideal MHD (magnetohydrodynamic) ballooning instabilities are impeded by a very small field line curvature and the line-tying condition. We, therefore, focus on non-ideal (resistive) effects in this study. The footpoints of coronal loops are constantly under random motions of convective scales, which twist individual loop strands quite randomly. The loop strands with the axial current of the same direction tend to coalesce by magnetic reconnection. In this reconnection process, the plasma in the loop system is redistributed in such a way that a smaller potential energy of the system is attained. We have performed numerical MHD simulations to investigate the plasma redistribution in coalescence of many small flux ropes. Our results clearly show that the redistributed plasma is more accumulated between flux ropes rather than near the magnetic axes of flux ropes. The Joule heating, however, creates a different temperature distribution than the density distribution. Our study may give a hint of which part of magnetic field we are looking to in an observation.