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Variation of Floating Potential in the Topside Ionosphere Observed by STSAT-1
Junhyun Lee,Ensang Lee,Jaejin Lee,Khan-Hyuk Kim,Jongho Seon,Dong-Hun Lee,Ho Jin,Eung-Hyun Kim,Hyun-Jin Jeon,Seong-Bin Lim,Taeyoun Kim,Jaewoong Jang,Kyung-Duk Jang,Kwangsun Ryu 한국우주과학회 2014 Journal of Astronomy and Space Sciences Vol.31 No.4
In this study, we investigated the effect of space plasmas on the floating potential variation of a low-altitude, polar-orbiting satellite using the Langmuir Probe (LP) measurement onboard the STSAT-1 spacecraft. We focused on small potential drops, for which the estimation of plasma density and temperature from LP is available. The floating potential varied according to the variations of plasma density and temperature, similar to the previously reported observations. Most of the potential drops occurred around the nightside auroral region. However, unlike the previous studies where large potential drops were observed with the precipitation of auroral electrons, the potential drops occurred before or after the precipitation of auroral electrons. Statistical analysis shows that the potential drops have good correlation with the temperature increase of cold electrons, which suggests the small potential drops be mainly controlled by the cold ionospheric plasmas.
Variation of Floating Potential in the Topside Ionosphere Observed by STSAT-1
Lee, Junhyun,Lee, Ensang,Lee, Jaejin,Kim, Khan-Hyuk,Seon, Jongho,Lee, Dong-Hun,Jin, Ho,Kim, Eung-Hyun,Jeon, Hyun-Jin,Lim, Seong-Bin,Kim, Taeyoun,Jang, Jaewoong,Jang, Kyung-Duk,Ryu, Kwangsun The Korean Space Science Society 2014 Journal of Astronomy and Space Sciences Vol.31 No.4
In this study, we investigated the effect of space plasmas on the floating potential variation of a low-altitude, polar-orbiting satellite using the Langmuir Probe (LP) measurement onboard the STSAT-1 spacecraft. We focused on small potential drops, for which the estimation of plasma density and temperature from LP is available. The floating potential varied according to the variations of plasma density and temperature, similar to the previously reported observations. Most of the potential drops occurred around the nightside auroral region. However, unlike the previous studies where large potential drops were observed with the precipitation of auroral electrons, the potential drops occurred before or after the precipitation of auroral electrons. Statistical analysis shows that the potential drops have good correlation with the temperature increase of cold electrons, which suggests the small potential drops be mainly controlled by the cold ionospheric plasmas.
Simulation and Quasi-Linear Theory of Whistler Anisotropy Instability
Lee, Sang-Yun,Lee, Ensang,Seough, Jungjoon,Lee, Jung-gi,Hwang, Junga,Lee, Jae-Jin,Cho, Kyung-Suk,Yoon, Peter H. American Geophysical Union 2018 Journal of geophysical research. Space physics Vol.123 No.5
<P>The whistler anisotropy (or electromagnetic electron cyclotron) instability may be operative in many geomagnetic and heliospherical environments, including the radiation belt, solar wind, and the solar corona. The present investigation carries out a comparative analysis between the two-dimensional particle-in-cell simulation of weakly growing whistler anisotropy instability and the velocity moment-based two-dimensional quasi-linear theory under the assumption of bi-Maxwellian electron distribution function. It is shown that the simplified quasi-linear theory provides a qualitative agreement with the more rigorous particle-in-cell simulation, but some discrepancies are also found. Possible causes for the differences in either method are discussed, and future improvements on the theory are suggested. Potential applicability of the present finding in the context of the space and astrophysics is discussed.</P>
Development and Test of 2.5-Dimensional Electromagnetic PIC Simulation Code
Sang-Yun Lee,Ensang Lee,Khan-Hyuk Kim,Jongho Seon,Dong-Hun Lee,Kwang-Sun Ryu 한국우주과학회 2015 Journal of Astronomy and Space Sciences Vol.32 No.1
We have developed a 2.5-dimensional electromagnetic particle simulation code using the particle-in-cell (PIC) method to investigate electromagnetic phenomena that occur in space plasmas. Our code is based on the leap-frog method and the centered difference method for integration and differentiation of the governing equations. We adopted the relativistic Buneman-Boris method to solve the Lorentz force equation and the Esirkepov method to calculate the current density while maintaining charge conservation. Using the developed code, we performed test simulations for electron two-stream instability and electron temperature anisotropy induced instability with the same initial parameters as used in previously reported studies. The test simulation results are almost identical with those of the previous papers.
Development and Test of 2.5-Dimensional Electromagnetic PIC Simulation Code
Lee, Sang-Yun,Lee, Ensang,Kim, Khan-Hyuk,Seon, Jongho,Lee, Dong-Hun,Ryu, Kwang-Sun The Korean Space Science Society 2015 Journal of Astronomy and Space Sciences Vol.32 No.1
We have developed a 2.5-dimensional electromagnetic particle simulation code using the particle-in-cell (PIC) method to investigate electromagnetic phenomena that occur in space plasmas. Our code is based on the leap-frog method and the centered difference method for integration and differentiation of the governing equations. We adopted the relativistic Buneman-Boris method to solve the Lorentz force equation and the Esirkepov method to calculate the current density while maintaining charge conservation. Using the developed code, we performed test simulations for electron two-stream instability and electron temperature anisotropy induced instability with the same initial parameters as used in previously reported studies. The test simulation results are almost identical with those of the previous papers.