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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.
MULTIPLE HARMONIC PLASMA EMISSION
Rhee, Tongnyeol,Ryu, Chang-Mo,Woo, Minho,Kaang, Helen H.,Yi, Sumin,Yoon, Peter H. IOP Publishing 2009 The Astrophysical journal Vol.694 No.1
<P>Electromagnetic radiation at the plasma frequency and/or its second harmonic, the so-called plasma emission, is widely accepted as the fundamental process responsible for solar type II and III radio bursts. There have also been occasional observations of higher-harmonic plasma emissions in the solar-terrestrial environment. This paper presents the first demonstration of multiple harmonic emission by means of two-dimensional electromagnetic particle-in-cell simulation. This finding indicates that under certain circumstances the traditional mechanism of fundamental-harmonic pair emission might also be accompanied by higher-harmonic components. Consequently, the present findings are highly relevant to in situ observations of third- and/or higher-harmonic plasma emission in astrophysical and solar-terrestrial environments.</P>
Radiation Pattern of Plasma Emission in Beam–Plasma Interaction
Rhee, Tongnyeol,Kim, Dae Ho,Ryu, Chang-Mo IEEE 2008 IEEE transactions on plasma science Vol.36 No.4
<P> The physical process of type-III solar radio bursts by an electron beam in a plasma involves electromagnetic radiation at the plasma frequency and its second harmonic. Recently, multiple-harmonic radiation of plasma frequency has drawn renewed interests in electromagnetic radiation in theoretical and numerical studies. The radiation pattern of electromagnetic waves in nonlinear beam–plasma interaction at the plasma frequency and its multiple harmonics is presented, by using a 2-D electromagnetic particle-in-cell simulation. </P>
Self-Consistent Generation of Superthermal Electrons by Beam-Plasma Interaction
Yoon, Peter H.,Rhee, Tongnyeol,Ryu, Chang-Mo American Physical Society 2005 Physical Review Letters Vol.95 No.21
<P>It has been known since the early days of plasma physics research that superthermal electrons are generated during beam-plasma laboratory experiments. Superthermal electrons (the kappa distribution) are also ubiquitously observed in space. To explain such a feature, various particle acceleration mechanisms have been proposed. However, self-consistent acceleration of electrons in the context of plasma kinetic theory has not been demonstrated to date. This Letter reports such a demonstration. It is shown that the collisionality, defined via the 'plasma parameter' g=1/n(lambda(D)(3), plays a pivotal role. It is found that a small but moderately finite value of is necessary for the superthermal tail to be generated, implying that purely collisionless (g=0) Vlasov theory cannot produce a superthermal population.</P>
유창모,M. Kwon,S. G. Lee,Tongnyeol Rhee 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.III
Ion saturation currents of a Hanbit mirror plasma measured by Langmuir probes, which are located at the edge of the plasma, have been analyzed by using the wavelet bispectral method. The bispectral analysis of low-frequency electrostatic turbulence shows a strong bicoherence at very low frequency, which indicates resonant three-wave coupling between the low-frequency modes in the phase space.=
차세대 중형 3호의 Magnetic Cleanliness Algorithm
최정림,이동렬,이승욱,최두영,유광선,Cheong Rim Choi,Tongnyeol Rhee,Seunguk Lee,Dooyoung Choi,Kwangsun Ryu 한국우주과학회 2023 우주기술과 응용 Vol.3 No.3
One of the important ways to improve the performance of magnetometers in satellite exploration is to reduce magnetic noise from satellites. One of the methods to decrease magnetic noise is by extending the satellite boom. However, this approach is often not preferred due to its high cost and operational considerations. Therefore, in many cases, removing interference from the satellite platform in the measured dataset is widely utilized after data acquisition. In this study, we would like to introduce an algorithm for removing magnetic noise observed from magnetometers installed on two solar panels and one main body without a boom.
Kaang, Helen H,Ryu, Chang-Mo,Rha, Kicheol,Rhee, Tongnyeol Published jointly by The Institute of Physics and 2012 Plasma physics and controlled fusion Vol.54 No.5
<P>Parametric instabilities of Alfvén-ion-cyclotron (AIC) waves and the turbulence driven by them are investigated using a particle-in-cell simulation technique. By introducing anisotropic ion temperature, a broad spectrum of AIC wave is excited. In addition to the normal AIC waves, their harmonic modes and upper sideband modes are found. Through the interaction of these Alfvénic waves and longitudinal electrostatic waves, Alfvénic turbulence is developed. Excitation of density and electromagnetic waves and their mode coupling structures are investigated using the ω–k spectrum and bicoherence analysis. It is found that the ion-acoustic wave is excited by the modulational instability, and that the ion density mode with a negative group velocity is excited in the high-k region by the decay instability. In addition, a longitudinal mode whose phase velocity behaves similarly to that of the ion-acoustic mode with a shifted wave number is found. This mode is identified as the second harmonic ion-acoustic wave. The inverse cascade structures of the electromagnetic and density fluctuations exhibit an interesting behavior that the density fluctuation shows a dual spectrum, whereas the electrostatic field E<SUB>x</SUB> shows a single spectrum.</P>
Shinohara, Kouji,Bierwage, Andreas,Suzuki, Yasuhiro,Kim, Junghee,Matsunaga, Go,Honda, Mitsuru,Rhee, Tongnyeol IOP 2018 Nuclear fusion. Fusion nucléaire. &n.Illiga Vol.58 No.8
<P>In order to account for the effect of field perturbations on the transport of fast ions in integrated codes used for the simulation of operational scenarios, it is crucial to develop computationally efficient reduced transport models. Such modeling efforts may greatly benefit from a simple method that determines the width of the island-like structures, which are produced by resonant perturbations in the phase space of the fast ion guiding centers and are known to play a key role for fast ion transport enhancement. In this paper, we present a method for estimating the widths of such ‘orbit islands’ for passing particles in the presence of static magnetic perturbations. The method consists of mapping the boundaries of magnetic islands from magnetic flux space (<img ALIGN='MIDDLE' ALT='' SRC='http://ej.iop.org/images/0029-5515/58/8/082026/nfaab170ieqn001.gif'/>) into the canonical angular momentum space (<img ALIGN='MIDDLE' ALT='' SRC='http://ej.iop.org/images/0029-5515/58/8/082026/nfaab170ieqn002.gif'/>) of the fast ions. As a working example, we consider co-passing neutral beam (NB) ions subject to a resonant magnetic perturbation (RMP) in a KSTAR tokamak plasma. The estimated orbit island width deviates by less than 25% from the value obtained from Poincaré plots of the actual guiding center trajectories, even when the magnetic drifts are large (here, up to 50% of the minor radius). Our analysis also shows that most of the fast ion transport can be attributed to the effect of isolated islands, which means that stochastization of particle trajectories due to resonance overlaps does not play a major role in the case studied here. The island mapping method proposed here eliminates the need to compute and analyze Poincaré maps of particle trajectories, so that computation times can be reduced tremendously by several orders of magnitude. A further speed-up may be achieved by the development of a method for estimating the width of magnetic islands under realistic conditions.</P>