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Electron Kinetic Property of a Magnetized Dual-Frequency Capacitively-Coupled Plasma
김대호,류창모,이성희,이재구 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.1
Spatially-resolved electron-energy-distribution functions (EEDFs) of a magnetized dual-frequency (60 and 2 MHz) capacitive discharge are numerically investigated by using a one-dimensional particle-in-cell/Monte Carlo collision simulation. It is shown that the electron kinetic property over the entire energy range changes from a nonlocal to a local regime, as the magnetic eld increases. This transition results from a reduction in the electron diusion in coordinate space and an enhancement of the electron diffusion in energy space due to an increase in the magnetic field. In an asymmetric discharge, it is found that the electron kinetic property near the 2 MHz electrode, which has a smaller electrode with an external capacitor, is more localized than that near the 60 MHz electrode.
Simulation study on the nonlinear evolution of EMIC instability
라기철,류창모,Rha, Kicheol,Ryu, Chang-Mo,Yoon, Peter H. 한국천문학회 2012 天文學會報 Vol.37 No.2
Charged particle energization is an outstanding problem in space physics. This paper investigates the nonlinear dynamics of Alfve'n-cyclotron waves accompanying particle heating processes and the drift Alfv'en-cyclotron (or EMIC) instability associated with a current disruption event on 29 January 2008 observed with THEMIS satellite by means of a particle-in-cell simulation. The simulation shows that the drift Alfv'en-cyclotron instabilities are excited in two regimes, a relatively low frequency mode propagating in a quasi-perpendicular direction while the second high-frequency branch propagating in a predominantly parallel propagation direction, which is consistent with observation as well as earlier theories. It is shown that parametric decay processes lead to an inverse cascade of Alfv'en-cyclotron waves and the generation of ion-acoustic waves by decay instability. It is also shown that the nonlinear decay processes are accompanied by small perpendicular heating and parallel cooling of the protons, and a pronounced parallel heating of the electrons.
Simulation Study of Plasma Emission in Beam-Plasma Interactions
Tongnyeol Rhee,Minho Woo,류창모 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.1
A two-dimensional electromagnetic particle-in-cell simulation of the beam-plasma interaction process is carried out to study the electromagnetic radiation at the plasma frequency and its second harmonic. In the simulation, a homogeneous plasma background with a periodic boundary condition is assumed. Electromagnetic radiation at the plasma frequency and its higher harmonics are widely believed to be responsible for solar type-II and type-III radio bursts. Traditional theory based upon weak turbulence of three-wave and nonlinear wave-particle interaction processes predicts radiation emission primarily at the fundamental and second harmonic of the plasma frequency. Electrostatic modes and electromagnetic radiation corresponding to this expectation at the fundamental and the second harmonics plasma frequencies are found. The radiation patterns of the fundamental and second harmonic electromagnetic modes are examined in detail.
Study of Nonlinear Electron Beam-Plasma Interaction Based on the Generalized Weak Turbulence Theory
Sumin Yi,Peter H. Yoon,류창모 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.1
Harmonic Langmuir waves and multiple harmonic plasma emission are interesting nonlinear phenomena that take place during the electron beam-plasma interaction process. It is difficult to explain these nonlinear phenomena within the framework of the customary weak turbulence theory, so we put forth a theoretical explanation in the framework of the "generalized" weak turbulence theory. On the basis on the wave kinetic equation governing the interaction of a transverse electromagnetic (EM) wave with nonlinear harmonic Langmuir waves, it is found that an EM wave with a frequency in the vicinity of higher harmonics of the plasma frequency is amplified as a result of a nonlinear wave-wave interaction between the EM and the harmonic Langmuir waves. The dependency of the EM emission at higher harmonics on the angle defined with respect to the beam's propagation direction is numerically examined by modeling the harmonic Langmuir wave spectrum.