scholarly journals Kinetic Simulations of Type II Radio Burst Emission Processes

2010 ◽  
Vol 6 (S274) ◽  
pp. 470-472 ◽  
Author(s):  
Urs Ganse ◽  
Felix Spanier ◽  
Rami Vainio
Keyword(s):  
Electromagnetic Waves ◽  
Plasma Frequency ◽  
Electron Beams ◽  
Langmuir Wave ◽  
Wave Interaction ◽  
Type Ii ◽  
Wave Excitation ◽  
Wave Processes ◽  
Particle In Cell ◽  
Theoretical Predictions

AbstractUsing a fully relativistic, 3D particle in cell code we have studied Langmuir- and electromagnetic wave processes in a CME foreshock plasma with counterstreaming electron beams. Langmuir wave excitation in resonance with the plasma frequency is observed, with timescales in accordance with theoretical predictions. However, no three wave interaction leading to emission of electromagnetic waves were detectable within the timeframe of our simulations.

scholarly journals Particle-in-Cell Simulations of High-Power THz Generator Based on the Collision of Strongly Focused Relativistic Electron Beams in Plasma

Photonics ◽  
2021 ◽  
Vol 8 (6) ◽  
pp. 172
Author(s):  
Vladimir Annenkov ◽  
Evgeny Berendeev ◽  
Evgeniia Volchok ◽  
Igor Timofeev
Keyword(s):  
Electromagnetic Waves ◽  
High Efficiency ◽  
Plasma Frequency ◽  
Electron Beams ◽  
Thz Radiation ◽  
Radiation Mechanisms ◽  
Particle In Cell ◽  
Relativistic Electron Beams ◽  
Nanosecond Pulses ◽  
Stream Instability

Based on particle-in-cell simulations, we propose to generate sub-nanosecond pulses of narrowband terahertz radiation with tens of MW power using unique properties of kiloampere relativistic (2 MeV) electron beams produced by linear induction accelerators. Due to small emittance of such beams, they can be focused into millimeter and sub-millimeter spots comparable in sizes with the wavelength of THz radiation. If such a beam is injected into a plasma, it becomes unstable against the two-stream instability and excites plasma oscillations that can be converted to electromagnetic waves at the plasma frequency and its harmonics. It is shown that several radiation mechanisms with high efficiency of power conversion (∼1%) come into play when the radial size of the beam–plasma system becomes comparable with the wavelength of the emitted waves.

scholarly journals Alfvén wave interaction with inhomogeneous plasmas: acceleration and energy cascade towards small-scales

2004 ◽  
Vol 22 (6) ◽  
pp. 2081-2096 ◽  
Author(s):  
V. Génot ◽  
P. Louarn ◽  
F. Mottez
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Waves ◽  
Wave Interaction ◽  
Skin Depth ◽  
Alfven Wave ◽  
Double Layers ◽  
Larmor Radius ◽  
Density Gradients ◽  
Particle In Cell ◽  
The Magnetic Field

Abstract. Investigating the process of electron acceleration in auroral regions, we present a study of the temporal evolution of the interaction of Alfvén waves (AW) with a plasma inhomogeneous in a direction transverse to the static magnetic field. This type of inhomogeneity is typical of the density cavities extended along the magnetic field in auroral acceleration regions. We use self-consistent Particle In Cell (PIC) simulations which are able to reproduce the full nonlinear evolution of the electromagnetic waves, as well as the trajectories of ions and electrons in phase space. Physical processes are studied down to the ion Larmor radius and electron skin depth scales. We show that the AW propagation on sharp density gradients leads to the formation of a significant parallel (to the magnetic field) electric field (E-field). It results from an electric charge separation generated on the density gradients by the polarization drift associated with the time varying AW E-field. Its amplitude may reach a few percents of the AW E-field. This parallel component accelerates electrons up to keV energies over a distance of a few hundred Debye lengths, and induces the formation of electron beams. These beams trigger electrostatic plasma instabilities which evolve toward the formation of nonlinear electrostatic structures (identified as electron holes and double layers). When the electrostatic turbulence is fully developed we show that it reduces the further wave/particle exchange. This sequence of mechanisms is analyzed with the program WHAMP, to identify the instabilities at work and wavelet analysis techniques are used to characterize the regime of energy conversions (from electromagnetic to electrostatic structures, from large to small length scales). This study elucidates a possible scenario to account for the particle acceleration and the wave dissipation in inhomogeneous plasmas. It would consist of successive phases of acceleration along the magnetic field, the development of an electrostatic turbulence, the thermalization and the heating of the plasma. Space plasma physics (charged particle motion and acceleration; numerical studies).

Multiple-Frequency Measurements of a Flare Continuum Event

1982 ◽  
Vol 4 (4) ◽  
pp. 389-392 ◽  
Author(s):  
R.D. Robinson
Keyword(s):  
Solar Flares ◽  
Electromagnetic Waves ◽  
Plasma Frequency ◽  
Close Association ◽  
Type Ii ◽  
Multiple Frequency ◽  
Langmuir Waves ◽  
Long Duration ◽  
Type Ii Radio Bursts ◽  
The Continuum

A type of metre-wavelength continuum is observed in close association with solar flares and Type II radio bursts. This continuum is stationary in position, often intense, of a long duration (occasionally lasting well over an hour) and highly polarized (Robinson and Smerd 1975; Robinson 1978). It is thought to be produced by the conversion of Langmuir waves to electromagnetic waves near the local plasma frequency. Because of its close association with Type II bursts, the class has been designated as Type II related flare continuum, or FCII. In this paper I examine a particularly clear example of such an event, with emphasis on the relation between the Type II and the start of the continuum.

scholarly journals Electromagnetic emission by subsequent processes L→L'+S and L+L'→T

2010 ◽  
Vol 6 (S274) ◽  
pp. 252-254 ◽  
Author(s):  
Marian Karlický ◽  
Miroslav Bárta
Keyword(s):  
Plasma Frequency ◽  
Langmuir Wave ◽  
Electromagnetic Emission ◽  
Small Region ◽  
Analytical Analysis ◽  
Particle In Cell ◽  
Early Stages

AbstractUsing a 2.5-D electromagnetic particle-in-cell (PIC) model, very early stages of a generation of the electromagnetic emission produced by a monochromatic Langmuir wave are studied. It is found that the electromagnetic emission, which is dominant on the harmonic of the plasma frequency, starts to be generated in a very small region of k-vectors. Later on the k-vectors of this emission are scattered around a ‘circle’ (in our 2-D case), given by the relations for the L+L'→T process. Analytical analysis of two subsequent processes L→L'+S a L+L'→T confirms these results.

scholarly journals Mode Conversion and Reflection of Langmuir Waves in an Inhomogeneous Solar Wind

2001 ◽  
Vol 18 (4) ◽  
pp. 355-360 ◽  
Author(s):  
A. J. Willes ◽  
Iver H. Cairns
Keyword(s):  
Solar Wind ◽  
Electromagnetic Waves ◽  
Plasma Frequency ◽  
Mode Conversion ◽  
Langmuir Wave ◽  
Solar Wind Plasma ◽  
Langmuir Waves ◽  
Transverse Electromagnetic ◽  
Solar Wind Parameters ◽  
Conversion Efficiencies

AbstractBeam-driven Langmuir waves in the solar wind are generated just above the electron plasma frequency, which fluctuates in the inhomogeneous solar wind plasma. Consequently, propagating Langmuir waves encounter regions in which the wave frequency is less than the local plasma frequency, where they can be reflected, mode converted to transverse electromagnetic waves, and trapped in density wells. The aim here is to investigate Langmuir wave reflection and mode conversion at a linear density gradient for typical solar wind parameters. It is shown that higher mode conversion efficiencies are possible than previously calculated, but that mode conversion occurs in a smaller region of parameter space. In addition, the possibility of detecting mode conversion with in situ spacecraft Langmuir wave observations is discussed.

scholarly journals Mildly relativistic magnetized shocks in electron-ion plasmas I. Electromagnetic shock structure

2020 ◽  
Author(s):  
Arianna Ligorini ◽  
Jacek Niemiec ◽  
Oleh Kobzar ◽  
Masanori Iwamoto ◽  
Artem Bohdan ◽  
...  
Keyword(s):  
Electromagnetic Waves ◽  
Large Scale ◽  
Scale Effects ◽  
Mean Field ◽  
Wave Amplification ◽  
Particle In Cell ◽  
Relativistic Shocks ◽  
Theoretical Predictions ◽  
The Mean ◽  
Effective Wave

Abstract Mildly relativistic shocks in magnetized electron-ion plasmas are investigated with 2D kinetic particle-in-cell simulations of unprecedentedly high resolution and large scale for conditions that may be found at internal shocks in blazar cores. Ion-scale effects cause corrugations along the shock surface whose properties somewhat depend on the configuration of the mean perpendicular magnetic field, that is either in or out of the simulation plane. We show that the synchrotron maser instability persists to operate in mildly relativistic shocks in agreement with theoretical predictions and produces coherent emission of upstream-propagating electromagnetic waves. Shock front ripples are excited in both mean-field configurations and they engender effective wave amplification. The interaction of these waves with upstream plasma generates electrostatic wakefields.

scholarly journals On the influence of Langmuir wave spectra on the spectra of electromagnetic waves generated in solar plasma with double plasma frequency

2021 ◽  
Vol 503 (4) ◽  
pp. 5740-5745
Author(s):  
Igor V Kudryavtsev ◽  
T I Kaltman
Keyword(s):  
Electromagnetic Wave ◽  
Electromagnetic Waves ◽  
Plasma Frequency ◽  
Langmuir Wave ◽  
Wave Spectra ◽  
Langmuir Waves ◽  
Solar Plasma ◽  
Transverse Electromagnetic

ABSTRACT In this paper, we consider the spectral dependences of transverse electromagnetic waves generated in solar plasma at the coalescence of Langmuir waves. It is shown that different spectra of Langmuir waves lead to characteristic types of transversal electromagnetic wave spectra, what makes it possible to diagnose the features of the spectra of Langmuir waves generated in solar plasma.

scholarly journals Three-wave Interactions Involving One Whistler

1975 ◽  
Vol 28 (1) ◽  
pp. 101 ◽  
Author(s):  
DB Melrose
Keyword(s):  
Radio Emission ◽  
Solar Corona ◽  
Plasma Frequency ◽  
Resonance Condition ◽  
Langmuir Wave ◽  
Wave Interaction ◽  
Whistler Wave ◽  
The Other ◽  
Wave Interactions ◽  
The Waves

Three-wave interactions in which one of the waves is a whistler and the other two are higher frequency waves are examined. The suggestion by Chiu (1970) and Chin (1972) that radio emission near the fundamental plasma frequency might arise in the solar corona from the coalescence of a whistler wave with a Langmuir wave is shown to be unacceptable because the resonance condition for the three-wave interaction cannot be satisfied.

Solar Second Harmonic Plasma Emission and the Head-on Approximation

1995 ◽  
Vol 12 (2) ◽  
pp. 197-201 ◽  
Author(s):  
A. J. Willes ◽  
P. A. Robinson ◽  
D. B. Melrose
Keyword(s):  
Narrow Band ◽  
Plasma Frequency ◽  
Second Harmonic ◽  
Langmuir Wave ◽  
Radio Bursts ◽  
Type Ii ◽  
Coalescence Process ◽  
Solar Radio Bursts ◽  
Langmuir Waves ◽  
Band Spectra

AbstractThe coalescence of two Langmuir waves, L and L′, produces emission at twice the plasma frequency in type II and type III solar radio bursts. The analysis of the coalescence process is usually simplified by assuming the head-on approximation, where the wavevectors of the coalescing waves satisfy kL′ ≈ −kL, corresponding to the two Langmuir waves meeting head on. However, this is not always a valid approximation, particularly when the peak of the Langmuir spectrum lies at small wavenumbers, for narrow band spectra, and for spectra with broad angular ranges. Realistic Langmuir wave spectra are used to investigate the effects of relaxing the head-on approximation.

scholarly journals A Study of Solar Flare Continuum Events Observed at Metre Wavelengths

1978 ◽  
Vol 31 (6) ◽  
pp. 533 ◽  
Author(s):  
RD Robinson
Keyword(s):  
Solar Flare ◽  
Large Amplitude ◽  
Langmuir Wave ◽  
Theoretical Models ◽  
Coulomb Scattering ◽  
Particle Interactions ◽  
Type Ii ◽  
Wave Processes ◽  
Langmuir Waves ◽  
Type Iv

This paper presents observations and an interpretation of solar flare continuum radiaHon. Two types are distinguished: FCM which often precedes a moving type IV burst, and FCII which often follows a type II burst. Theoretical models are proposed for the two types of flare continuum event. For FCM events, the electrons are assumed to be injected into coronal arches, where they are confined by Coulomb scattering and wave-particle interactions. The radiation is due to either gyrosynchrotron or Langmuir wave processes. For FCII events, the electrons are assumed to be accelerated by large amplitude Alfvenic turbulence, the resultant radiation being caused by the conversion of Langmuir waves to electromagnetic radiation at the fundamental.

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