• Journal of Astronomy and Space Sciences
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• 제32권1호
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• pp.1-11
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• 2015

Earth's magnetopause separating the fast and often turbulent magnetosheath and the relatively stagnant magnetosphere provides various forms of free energy that generate low-frequency surface waves. The source mechanism of this energy includes current-driven kinetic physical processes such as magnetic reconnection on the dayside magnetopause and flux transfer events drifting along the magnetopause, and velocity shear-driven (Kelvin-Helmholtz instability) or density/pressure gradient-driven (Rayleigh-Taylor instability) magnetohydro-dynamics (MHD) instabilities. The solar wind external perturbations (impulsive transient pressure pulses or quasi-periodic dynamic pressure variations) act as seed fluctuations for the magnetopause waves and trigger ULF pulsations inside the magnetosphere via global modes or mode conversion at the magnetopause. The magnetopause waves thus play an important role in the solar wind-magnetosphere coupling, which is the key to space weather. This paper presents recent findings regarding the generation of surface waves (e.g., Kelvin-Helmholtz waves) at the Earth's magnetopause and analytic and observational studies accountable for the linking of the magnetopause waves and inner magnetospheric ULF pulsations, and the impacts of magnetopause waves on the dynamics of the magnetopause and on the inner magnetosphere.

• 천문학회보
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• 제36권1호
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• pp.33.1-33.1
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• 2011

The plasma sheet of the Earth's magnetosphere is a sheet of hot plasmas in the magnetotail region, dividing the two (northern and southern) lobes of the Earth's magnetic field. It is the key region that is often closely linked to various electromagnetic dynamics in the Earth's magnetosphere-ionosphere system. In particular, it is the region that is most crucial for substorms, which is one of the most dynamic phenomena in the Earth's magnetosphere. The question of substorm triggering remains highly controversial until today, and at the center of the controversy there are several critical physics issues of the plasma sheet. In this talk I will introduce some of the physics issues of the plasma sheet. The specific topics that this talk will cover are (i) the general properties of the plasma sheet, (ii) fast plasma jets and plasma transport problem, (iii) stability/instability problem, and (iv) effects of thin current sheet. I will also present some of our group's recent findings regarding these topics, as obtained by comprehensive analyses of various observational data. The level and content of this talk are designed to be comprehensible to not only space physicists but also the scientists in a related field such as solar and heliospheric physics.

• 우주기술과 응용
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• 제3권1호
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• pp.1-25
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• 2023

In this paper, I briefly introduce recently terminated, current, and future scientific spacecraft missions for in situ and remote-sensing observations of Earth's and other planetary magnetospheres as of February 2023. The spacecraft introduced here are Geotail, Cluster, Time History of Events and Macroscale Interactions during Substorms / Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon's Interaction with the Sun (THEMIS / ARTEMIS), Magnetospheric Multiscale (MMS), Exploration of energization and Radiation in Geospace (ERG), Cusp Plasma Imaging Detector (CuPID), and EQUilibriUm Lunar-Earth point 6U Spacecraft (EQUULEUS) for recently terminated or currently operated missions for Earth's magnetosphere; Lunar Environment Heliospheric X-ray Imager (LEXI), Gateway, Solar wind Magneto-sphere Ionosphere Link Explorer (SMILE), HelioSwarm, Solar-Terrestrial Observer for the Response of the Magnetosphere (STORM), Geostationary Transfer Orbit Satellite (GTOSat), GEOspace X-ray imager (GEO-X), Plasma Observatory, Magnetospheric Constellation (MagCon), self-Adaptive Magnetic reconnection Explorer (AME), and COnstellation of Radiation BElt Survey (CORBES) approved for launch or proposed for future missions for Earth's magnetosphere; BepiColombo for Mercury and Juno for Jupiter for current missions for planetary magnetospheres; Jupiter Icy Moons Explorer (JUICE) and Europa Clipper for Jupiter, Uranus Orbiter and Probe (UOP) for Uranus, and Neptune Odyssey for Neptune approved for launch or proposed for future missions for planetary magnetospheres. I discuss the recent trend and future direction of spacecraft missions as well as remaining challenges in magnetospheric research. I hope this paper will be a handy guide to the current status and trend of magnetospheric missions.

• 천문학회지
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• 제34권4호
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• pp.317-319
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• 2001

The response of the earth's magnetosphere to the variation of the solar wind parameters and Interplanetary magnetic field (IMF) has been stud}ed by using a high-resolution, three-dimension magnetohydrodynamic (MHD) simulation when the WIND data of velocity Vx, plasma density, dynamic pressure, By and Bz every 1 minute were used as input. Large electrojet and magnetic storm which occurred on October 21 and 22 are reproduced in the simulation (fig. 1). We have studied the energy transfer and tail reconnect ion in association with geomagnetic storms.

• 천문학회보
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• 제36권2호
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• pp.100.2-100.2
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• 2011

The dynamical evolution of the Earth's magnetosphere loaded with a transiently enhanced ring current is studied by numerical magnetohydrodynamic (MHD) simulation. Two cases with different values of the primitive ring current are considered. In one case, the initial ring current is strong enough to create a magnetic island in the magnetosphere. The magnetic island readily reconnects with the earth-connected ambient field and is destroyed as the system approaches a steady equilibrium. In the other case, the initial ring current is not so strong, and the initial magnetic field configuration bears no magnetic island, but a wake of bent field lines, which is smoothed out through the relaxing evolution of the magnetosphere. The relaxation time of the magnetosphere is found to be about five to six minutes, over which the ring current is reduced to about a quarter of its initial value. Before reaching a steady state, the magnetosphere is found to undergo an overshooting expansion and a subsequent contraction. Fast and slow magnetosonic waves are identified to play an important role in the relaxation toward equilibrium.

• 천문학회보
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• 제39권1호
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• pp.29-29
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• 2014

A fundamental problem in space physics is to explain the origin of energetic charged particles in space close to the Earth and the significant temporal variations of their flux. The particles are primarily electrons and protons although energetic heavy ions such as O+ are sometimes non-negligible. By "energetic" we mean a rather broad energy range of particles from a few tens of keV to well above MeV. Drastic variations of the particle fluxes (by >3 orders of magnitude) occur over both a short time scale like a few minutes and a long time scale like the 11-year sunspot cycle. In this talk I will focus on relativistic energy electrons (~MeV) trapped within the Earth's magnetosphere. They are a primary element of the space weather since they can cause damage to satellites, so often called "killer electrons". Considering that the source particles in both the solar wind and the ionosphere are relatively cold (~eV), the quasi-permanent existence of these very energetic particles close to the Earth has been a surprise to space physicists for decades. Complex electromagnetic processes such as wave-particle interactions within the magnetosphere are believed to play a major role in generating these killer electrons. While detailed physics remains an active research area, for this lecture I will introduce a synthesized picture of how solar activities are related to wave-particle interaction physics inside the magnetosphere. This can be applied to other astrophysical systems.

• 천문학회보
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• 제32권2호
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• pp.35.1-35.1
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• 2007

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2004년도 한국우주과학회보 제13권2호
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• pp.61-61
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• 2004

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2006년도 한국우주과학회보 제15권2호
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• pp.48-48
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• 2006

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2006년도 한국우주과학회보 제15권2호
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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.