scholarly journals Determining the wavelength of Langmuir wave packets at the Earth's bow shock

2011 ◽  
Vol 29 (3) ◽  
pp. 613-617 ◽  
Author(s):  
V. V. Krasnoselskikh ◽  
T. Dudok de Wit ◽  
S. D. Bale
Keyword(s):  
Wave Packets ◽  
Energetic Electron ◽  
Langmuir Wave ◽  
Field Measurements ◽  
Solar Wind Plasma ◽  
Density Fluctuations ◽  
Standard Theory ◽  
Langmuir Waves ◽  
High Frequency Electric Field ◽  
Earth’S Bow Shock

Abstract. The propagation of Langmuir waves in plasmas is known to be sensitive to density fluctuations. Such fluctuations may lead to the coexistence of wave pairs that have almost opposite wave-numbers in the vicinity of their reflection points. Using high frequency electric field measurements from the WIND satellite, we determine for the first time the wavelength of intense Langmuir wave packets that are generated upstream of the Earth's electron foreshock by energetic electron beams. Surprisingly, the wavelength is found to be 2 to 3 times larger than the value expected from standard theory. These values are consistent with the presence of strong inhomogeneities in the solar wind plasma rather than with the effect of weak beam instabilities.

scholarly journals On nonstationarity and rippling of the quasiperpendicular zone of the Earth bow shock: Cluster observations

2008 ◽  
Vol 26 (9) ◽  
pp. 2899-2910 ◽  
Author(s):  
V. V. Lobzin ◽  
V. V. Krasnoselskikh ◽  
K. Musatenko ◽  
T. Dudok de Wit
Keyword(s):  
Electric Field ◽  
Shock Front ◽  
Energetic Electron ◽  
Bow Shock ◽  
Langmuir Waves ◽  
Shock Surface ◽  
High Frequency Electric Field ◽  
Earth’S Bow Shock ◽  
Hidden Periodicities ◽  
Field Fluctuations

Abstract. A new method for remote sensing of the quasiperpendicular part of the bow shock surface is presented. The method is based on analysis of high frequency electric field fluctuations corresponding to Langmuir, upshifted, and downshifted oscillations in the electron foreshock. Langmuir waves usually have maximum intensity at the upstream boundary of this region. All these waves are generated by energetic electrons accelerated by quasiperpendicular zone of the shock front. Nonstationary behavior of the shock, in particular due to rippling, should result in modulation of energetic electron fluxes, thereby giving rise to variations of Langmuir waves intensity. For upshifted and downshifted oscillations, the variations of both intensity and central frequency can be observed. For the present study, WHISPER measurements of electric field spectra obtained aboard Cluster spacecraft are used to choose 48 crossings of the electron foreshock boundary with dominating Langmuir waves and to perform for the first time a statistical analysis of nonstationary behavior of quasiperpendicular zone of the Earth's bow shock. Analysis of hidden periodicities in plasma wave energy reveals shock front nonstationarity in the frequency range 0.33 fBi<f<fBi, where fBi is the proton gyrofrequency upstream of the shock, and shows that the probability to observe such a nonstationarity increases with Mach number. The profiles observed aboard different spacecraft and the dominating frequencies of the periodicities are usually different. Hence nonstationarity and/or rippling seem to be rather irregular both in space and time rather than resembling a quasiregular wave propagating on the shock surface.

scholarly journals Turbulence and Microprocesses in Inhomogeneous Solar Wind Plasmas

Fluids ◽  
2019 ◽  
Vol 4 (2) ◽  
pp. 69 ◽  
Author(s):  
Catherine Krafft ◽  
Alexander S. Volokitin ◽  
Gaëtan Gauthier
Keyword(s):  
Solar Wind ◽  
Energetic Electron ◽  
Langmuir Wave ◽  
Solar Wind Plasma ◽  
Density Fluctuations ◽  
Wave Radiation ◽  
Wave Turbulence ◽  
Small Scale ◽  
The Impact ◽  
The Waves

The random density fluctuations observed in the solar wind plasma crucially influence on the Langmuir wave turbulence generated by energetic electron beams ejected during solar bursts. Those are powerful phenomena consisting of a chain of successive processes leading ultimately to strong electromagnetic emissions. The small-scale processes governing the interactions between the waves, the beams and the inhomogeneous plasmas need to be studied to explain such macroscopic phenomena. Moreover, the complexity induced by the plasma irregularities requires to find new approaches and modelling. Therefore theoretical and numerical tools were built to describe the Langmuir wave turbulence and the beam’s dynamics in inhomogeneous plasmas, in the form of a self-consistent Hamiltonian model including a fluid description for the plasma and a kinetic approach for the beam. On this basis, numerical simulations were performed in order to shed light on the impact of the density fluctuations on the beam dynamics, the electromagnetic wave radiation, the generation of Langmuir wave turbulence, the waves’ coupling and decay phenomena involving Langmuir and low frequency waves, the acceleration of beam electrons, their diffusion mechanisms, the modulation of the Langmuir waveforms and the statistical properties of the radiated fields’ distributions. The paper presents the main results obtained in the form of a review.

Nonlinear Landau damping of large-amplitude Langmuir waves and formation of standing nonlinear waves

1980 ◽  
Vol 23 (3) ◽  
pp. 475-482 ◽  
Author(s):  
V. P. Pavlenko
Keyword(s):  
Thermal Plasma ◽  
Nonlinear Waves ◽  
Wave Packets ◽  
Langmuir Wave ◽  
Landau Damping ◽  
Characteristic Scale ◽  
Langmuir Waves ◽  
Slowing Down ◽  
Mechanism Of Interaction ◽  
Nonlinear Landau Damping

The interaction of nonlinear Langmuir wave packets corresponding to periodic solutions of the nonlinear Schrödinger equation with thermal plasma particles is considered. The mechanism of interaction is nonlinear Landau damping. The wave packets are slowed down owing to interaction but their amplitudes remain essentially unchanged. The characteristic scale lengths of the slowing down are determined.

Solar type III radio burst fine structure from Langmuir wave motion through turbulent plasma

2021 ◽  
Author(s):  
Eduard Kontar ◽  
Hamish Reid
Keyword(s):  
Fine Structure ◽  
Solar Corona ◽  
Interplanetary Space ◽  
Langmuir Wave ◽  
Turbulent Medium ◽  
Density Fluctuations ◽  
Solar Radio Emission ◽  
Langmuir Waves ◽  
Type Iii ◽  
Diagnostic Potential

&lt;div&gt;The Sun frequently accelerates near-relativistic electron beams that travel out through the solar corona and interplanetary space. Interacting with their plasma environment, these beams produce type III radio bursts, the brightest astrophysical radio sources detected by humans. The formation and motion of type III fine frequency structures is a puzzle but is commonly believed to be related to plasma turbulence in the solar corona and solar wind. Combining a theoretical framework with kinetic simulations and high-resolution radio type III observations, we quantitatively show that the fine structures are caused by the moving intense clumps of Langmuir waves in a turbulent medium. Our results show how type III fine structure can be used to remotely analyse the intensity and spectrum of compressive density fluctuations, and can infer ambient temperatures in astrophysical plasma, both significantly expanding the current diagnostic potential of solar radio emission.&lt;/div&gt;&lt;div&gt;&amp;#160;&lt;/div&gt;

scholarly journals Fundamental Electromagnetic Emissions by a Weak Electron Beam in Solar Wind Plasmas with Density Fluctuations

2022 ◽  
Vol 924 (2) ◽  
pp. L24
Author(s):  
C. Krafft ◽  
P. Savoini
Keyword(s):  
Electron Beam ◽  
Electromagnetic Radiation ◽  
Inhomogeneous Plasma ◽  
Langmuir Wave ◽  
Density Fluctuations ◽  
Electromagnetic Energy ◽  
Langmuir Waves ◽  
Harmonic Emission ◽  
Electromagnetic Emissions ◽  
Weak Electron

Abstract The generation of Langmuir wave turbulence by a weak electron beam in a randomly inhomogeneous plasma and its subsequent electromagnetic radiation are studied owing to two-dimensional particle-in-cell simulations in conditions relevant to type III solar radio bursts. The essential impact of random density fluctuations of average levels of a few percents of the background plasma on the characteristics of the electromagnetic radiation at the fundamental plasma frequency ω p is shown. Not only wave nonlinear interactions but also processes of Langmuir waves’ transformations on the density fluctuations contribute to the generation of such emissions. During the beam relaxation, the amount of electromagnetic energy radiated at ω p in a plasma with density fluctuations strongly exceeds that observed when the plasma is homogeneous. The fraction of Langmuir wave energy involved in the generation of electromagnetic emissions at ω p saturates around 10−4, i.e., one order of magnitude above that reached when the plasma is uniform. Moreover, whereas harmonic emission at 2ω p dominates over fundamental emission during the time evolution in a homogeneous plasma, fundamental emission is strongly dominant when the plasma contains density fluctuations, at least during several thousands of plasma periods before being overcome by harmonic emission when the total electromagnetic energy begins to saturate.

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 Large-Scale Structure and Termination of the Heliosphere

1998 ◽  
Vol 11 (2) ◽  
pp. 851-856 ◽  
Author(s):  
W. M. Macek
Keyword(s):  
Solar Wind ◽  
Large Scale ◽  
Second Harmonic ◽  
Source Region ◽  
Langmuir Wave ◽  
Solar Wind Plasma ◽  
Langmuir Waves ◽  
Post Shock ◽  
Wind Intensity

AbstractThe question of the boundaries of the heliosphere is considered. The termination heliospheric shock should exist because the solar wind plasma flowing supersonically away from the Sun must make a transition to a subsonic flow. The heliopause is at the outermost extend of the solar wind. Beyond the heliopause lies the (very local) interstellar wind. Intensity of radio emissions at 2 to 3 kHz detected by the Voyager plasma wave instrument in the outer heliosphere can be explained provided that the electron beams generating Langmuir waves exist in the post-shock plasma due to secondary shocks in the compressed solar wind beyond the termination shock. The field strengths of Langmuir waves required to generate the second harmonic emissions are 50 – 100 μ V m-1. Alternatively, the emissions are generated in the vicinity of the heliopause. The Voyager 1 and 2 are proceeding toward a likely source region for Langmuir wave and these waves may be observed in situ in the near future.

Statistical Analysis of Langmuir Waves Associated with Type III Radio Bursts: II. Simulation and Interpretation of the Wave Energy Distributions

2011 ◽  
Vol 20 (4) ◽  
Author(s):  
M. Maksimović ◽  
S. Vidojević ◽  
A. Zaslavsky
Keyword(s):  
Wave Energy ◽  
Probability Distributions ◽  
Wave Packets ◽  
Low Frequency ◽  
Langmuir Wave ◽  
Type I ◽  
Energy Distributions ◽  
Langmuir Waves ◽  
Pearson Type ◽  
Log Normal

AbstractWe have modeled electrostatic Langmuir waves by an electric field, consisting of superposition of Gaussian wave packets with several probability distributions of amplitudes and with several Poisson distributions of wave packets. The outcome of the model is that the WIND satellite observations, especially in the low frequency domain (the WAVES experiment), do not allow to conclude whether the input wave amplitude distributions are closer to the log-normal than to the Pearson type I or uniform. The average number of wave packets in 1 s is found to be between 0.1 and 50. Therefore, there is a clear need to measure Langmuir wave energy distributions directly at the waveform level, not a posteriori in the spectral domain. This is planned to be implemented on the RPW (Radio and Plasma Wave Analyzer) instrument in the Solar Orbiter mission.

scholarly journals Vlasov simulation of Langmuir wave packets

2007 ◽  
Vol 14 (5) ◽  
pp. 671-679 ◽  
Author(s):  
T. Umeda
Keyword(s):  
Wave Packets ◽  
Langmuir Wave ◽  
Formation Processes ◽  
Ion Distribution ◽  
Langmuir Waves ◽  
One Dimensional ◽  
History Of ◽  
Turbulent Process ◽  
Weak Electron ◽  
Trapping Process

Abstract. Amplitude modulation and packet formation of Langmuir waves are commonly observed during a nonlinear interaction between electron beams and plasmas. In this paper, we briefly review the history of Langmuir wave packets as developed by recent spacecraft observations and computer simulations. New one-dimensional electrostatic Vlasov simulations are performed to study their formation processes. It is found that the formation of Langmuir wave packets involves both an incoherent turbulent process and a coherent nonlinear trapping process. Existence of cold ions does not affect nonlinear processes of the weak-electron-beam instability in which the ion distribution is hardly modified by the excited Langmuir wave packets.

scholarly journals Particle-in-cell simulations of the relaxation of electron beams in inhomogeneous solar wind plasmas

2016 ◽  
Vol 82 (6) ◽  
Author(s):  
Jonathan O. Thurgood ◽  
David Tsiklauri
Keyword(s):  
Solar Wind ◽  
Electron Beam ◽  
Linear Theory ◽  
Langmuir Wave ◽  
High Energy ◽  
Density Fluctuations ◽  
Langmuir Waves ◽  
Particle In Cell ◽  
Hamiltonian Models ◽  
Beam Plasma

Previous theoretical considerations of electron beam relaxation in inhomogeneous plasmas have indicated that the effects of the irregular solar wind may account for the poor agreement of homogeneous modelling with the observations. Quasi-linear theory and Hamiltonian models based on Zakharov’s equations have indicated that when the level of density fluctuations is above a given threshold, density irregularities act to de-resonate the beam–plasma interaction, restricting Langmuir wave growth on the expense of beam energy. This work presents the first fully kinetic particle-in-cell (PIC) simulations of beam relaxation under the influence of density irregularities. We aim to independently determine the influence of background inhomogeneity on the beam–plasma system, and to test theoretical predictions and alternative models using a fully kinetic treatment. We carry out one-dimensional (1-D) PIC simulations of a bump-on-tail unstable electron beam in the presence of increasing levels of background inhomogeneity using the fully electromagnetic, relativistic EPOCH PIC code. We find that in the case of homogeneous background plasma density, Langmuir wave packets are generated at the resonant condition and then quasi-linear relaxation leads to a dynamic increase of wavenumbers generated. No electron acceleration is seen – unlike in the inhomogeneous experiments, all of which produce high-energy electrons. For the inhomogeneous experiments we also observe the generation of backwards-propagating Langmuir waves, which is shown directly to be due to the refraction of the packets off the density gradients. In the case of higher-amplitude density fluctuations, similar features to the weaker cases are found, but also packets can also deviate from the expected dispersion curve in $(k,\unicode[STIX]{x1D714})$-space due to nonlinearity. Our fully kinetic PIC simulations broadly confirm the findings of quasi-linear theory and the Hamiltonian model based on Zakharov’s equations. Strong density fluctuations modify properties of excited Langmuir waves altering their dispersion properties.

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