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Langmuir condensation by spontaneous scattering off electrons in two dimensions
Ziebell, L F,Yoon, P H,Gaelzer, R,Pavan, J Published jointly by The Institute of Physics and 2012 Plasma physics and controlled fusion Vol.54 No.5
<P>In a pair of recent papers (Ziebell et al 2008 Phys. Plasmas 15 032303, 2008 Plasma Phys. Control. Fusion 50 085011) it was shown, within the context of weak turbulence theory, that the Langmuir turbulence generated by the bump-in-tail instability does not lead to Langmuir condensation (or accumulation of wave energy and momentum in the long-wavelength regime) in two dimensions. The present analysis finds that it is important to include the spontaneous scattering off Langmuir turbulence of the electrons, which is ignored in the customary literature when compared with a similar process involving ions, in order to recover the condensation of Langmuir waves in two dimensions.</P>
PLASMA EMISSION BY WEAK TURBULENCE PROCESSES
Ziebell, L. F.,Yoon, P. H.,Gaelzer, R.,Pavan, J. IOP Publishing 2014 ASTROPHYSICAL JOURNAL LETTERS - Vol.795 No.2
<P>The plasma emission is the radiation mechanism responsible for solar type II and type III radio bursts. The first theory of plasma emission was put forth in the 1950s, but the rigorous demonstration of the process based upon first principles had been lacking. The present Letter reports the first complete numerical solution of electromagnetic weak turbulence equations. It is shown that the fundamental emission is dominant and unless the beam speed is substantially higher than the electron thermal speed, the harmonic emission is not likely to be generated. The present findings may be useful for validating reduced models and for interpreting particle-in-cell simulations.</P>
PLASMA EMISSION BY NONLINEAR ELECTROMAGNETIC PROCESSES
Ziebell, L. F.,Yoon, P. H.,Petruzzellis, L. T.,Gaelzer, R.,Pavan, J. IOP Publishing 2015 The Astrophysical journal Vol.806 No.2
<P>The plasma emission, or electromagnetic (EM) radiation at the plasma frequency and/or its harmonic(s), is generally accepted as the radiation mechanism responsible for solar type II and III radio bursts. Identification and characterization of these solar radio burst phenomena were done in the 1950s. Despite many decades of theoretical research since then, a rigorous demonstration of the plasma emission process based upon first principles was not available until recently, when, in a recent Letter, Ziebell et al. reported the first complete numerical solution of EM weak turbulence equations; thus, quantitatively analyzing the plasma emission process starting from the initial electron beam and the associated beam-plasma (or Langmuir wave) instability, as well as the subsequent nonlinear conversion of electrostatic Langmuir turbulence into EM radiation. In the present paper, the same problem is revisited in order to elucidate the detailed physical mechanisms that could not be reported in the brief Letter format. Findings from the present paper may be useful for interpreting observations and full-particle numerical simulations.</P>
PLASMA EMISSION BY COUNTER-STREAMING ELECTRON BEAMS
Ziebell, L. F.,Petruzzellis, L. T.,Yoon, P. H.,Gaelzer, R.,Pavan, J. American Astronomical Society 2016 The Astrophysical Journal Vol.818 No.1
<P>The radiation emission mechanism responsible for both type-II and type-III solar radio bursts is commonly accepted as plasma emission. Recently Ganse et al. suggested that type-II radio bursts may be enhanced when the electron foreshock geometry of a coronal mass ejection contains a double hump structure. They reasoned that the counter-streaming electron beams that exist between the double shocks may enhance the nonlinear coalescence interaction, thereby giving rise to more efficient generation of radiation. Ganse et al. employed a particle-in-cell simulation to study such a scenario. The present paper revisits the same problem with EM weak turbulence theory, and show that the fundamental (F) emission is not greatly affected by the presence of counter-streaming beams, but the harmonic (H) emission becomes somewhat more effective when the two beams are present. The present finding is thus complementary to the work by Ganse et al.</P>