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.

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 Ion-driven Instabilities in the Inner Heliosphere. I. Statistical Trends

2021 ◽  
Vol 923 (1) ◽  
pp. 116
Author(s):  
Mihailo M. Martinović ◽  
Kristopher G. Klein ◽  
Tereza Ďurovcová ◽  
Benjamin L. Alterman
Keyword(s):  
Solar Wind ◽  
Particle Interaction ◽  
Radial Distance ◽  
Solar Wind Plasma ◽  
Distribution Functions ◽  
Nyquist Criterion ◽  
Velocity Distribution Functions ◽  
Instability Growth ◽  
Statistical Trends ◽  
The Impact

Abstract Instabilities described by linear theory characterize an important form of wave–particle interaction in the solar wind. We diagnose unstable behavior of solar wind plasma between 0.3 and 1 au via the Nyquist criterion, applying it to fits of ∼1.5M proton and α particle Velocity Distribution Functions (VDFs) observed by Helios I and II. The variation of the fraction of unstable intervals with radial distance from the Sun is linear, signaling a gradual decline in the activity of unstable modes. When calculated as functions of the solar wind velocity and Coulomb number, we obtain more extreme, exponential trends in the regions where collisions appear to have a notable influence on the VDF. Instability growth rates demonstrate similar behavior, and significantly decrease with Coulomb number. We find that for a nonnegligible fraction of observations, the proton beam or secondary component might not be detected, due to instrument resolution limitations, and demonstrate that the impact of this issue does not affect the main conclusions of this work.

scholarly journals Energetic particle parallel diffusion in a cascading wave turbulence in the foreshock region

2007 ◽  
Vol 14 (5) ◽  
pp. 587-601 ◽  
Author(s):  
F. Otsuka ◽  
Y. Omura ◽  
O. Verkhoglyadova
Keyword(s):  
Solar Wind ◽  
Pitch Angle ◽  
Homogeneous Model ◽  
Bow Shock ◽  
Isotropic Scattering ◽  
Wave Turbulence ◽  
Small Scale ◽  
Dimensional System ◽  
Inverse Cascade ◽  
Background Magnetic Field

Abstract. We study parallel (field-aligned) diffusion of energetic particles in the upstream of the bow shock with test particle simulations. We assume parallel shock geometry of the bow shock, and that MHD wave turbulence convected by the solar wind toward the shock is purely transverse in one-dimensional system with a constant background magnetic field. We use three turbulence models: a homogeneous turbulence, a regular cascade from a large scale to smaller scales, and an inverse cascade from a small scale to larger scales. For the homogeneous model the particle motions along the average field are Brownian motions due to random and isotropic scattering across 90 degree pitch angle. On the other hand, for the two cascade models particle motion is non-Brownian due to coherent and anisotropic pitch angle scattering for finite time scale. The mean free path λ|| calculated by the ensemble average of these particle motions exhibits dependence on the distance from the shock. It also depends on the parameters such as the thermal velocity of the particles, solar wind flow velocity, and a wave turbulence model. For the inverse cascade model, the dependence of λ|| at the shock on the thermal energy is consistent with the hybrid simulation done by Giacalone (2004), but the spatial dependence of λ|| is inconsistent with it.

scholarly journals The small amplitude of density turbulence in the inner solar wind

2003 ◽  
Vol 10 (1/2) ◽  
pp. 113-120 ◽  
Author(s):  
S. R. Spangler
Keyword(s):  
Solar Wind ◽  
Spatial Scales ◽  
Power Spectra ◽  
Solar Wind Plasma ◽  
Density Fluctuations ◽  
Long Baseline ◽  
Interferometer Phase ◽  
The Mean ◽  
Pass Through ◽  
Rms Amplitude

Abstract. Very Long Baseline Interferometer (VLBI) observations were made of radio sources close to the Sun, whose lines of sight pass through the inner solar wind (impact parameters 16-26 RE). Power spectra were analyzed of the interferometer phase fluctuations due to the solar wind plasma. These power spectra provide information on the level of plasma density fluctuations on spatial scales of roughly one hundred to several thousand kilometers. By specifying an outer scale to the turbulence spectrum, we can estimate the root-mean-square (rms) amplitude of the density fluctuations. The data indicate that the rms fluctuation in density is only about 10% of the mean density. This value is low, and consistent with extrapolated estimates from more distant parts of the solar wind. Physical speculations based on this result are presented.

Non-adiabatic interaction of ions with solar wind discontinuities

2020 ◽  
Author(s):  
Alexander Vinogradov ◽  
Anton Artemyev ◽  
Ivan Vasko ◽  
Alexei Vasiliev ◽  
Anatoly Petrukovich
Keyword(s):  
Solar Wind ◽  
Observational Data ◽  
Solar Wind Plasma ◽  
Theoretical Models ◽  
High Amplitude ◽  
Small Scale ◽  
Ion Scattering ◽  
Ion Temperature ◽  
Wide Range ◽  
Radial Evolution

<p>According to Helios, Ulysses, New Horizons measurements at a wide range of distances from the Sun, radial evolution of solar wind ion temperature significantly deviates from the adiabatic expansion model:  additional heating of the solar wind plasma is required to describe observational data. Solution of the solar wind heating problem is extremely important both for understanding the structure of the heliosphere and for adequately describing the atmospheres of distant stars. Solar wind magnetic field is turbulent and this turbulence is dominated by numerous small-scale high-amplitude coherent structures – such as quasi-1D discontinuities. Modern theoretical models predict that quasi-1D discontinuities can play important role in solar wind heating. We collected the statistics of MMS observations of thin quasi-1D discontinuities in the solar wind to reveal their characteristics. Analyzing observational data, we construct the discontinuity model and use it to consider non-adiabatic interaction of ions with solar wind discontinuities. We mainly focus on discontinuity roles in solar wind ion scattering and thermalization. This presentation shows how discontinuity configuration affects the scattering rates.</p>

scholarly journals Dispersive magnetized waves in the solar wind plasma

2010 ◽  
Vol 77 (3) ◽  
pp. 357-365 ◽  
Author(s):  
B. DASGUPTA ◽  
DASTGEER SHAIKH ◽  
P. K. SHUKLA
Keyword(s):  
Solar Wind ◽  
Dispersion Relation ◽  
Fluid Model ◽  
Phase Speed ◽  
Solar Wind Plasma ◽  
Small Scale ◽  
Linear Dispersion ◽  
Length Scales ◽  
Linear Dispersion Relation ◽  
Two Fluid Model

AbstractWe derive a generalized linear dispersion relation of waves in a strongly magnetized, compressible, homogeneous and isotropic quasi-neutral plasma. Starting from a two-fluid model, describing distinguishable electron and ion fluids, we obtain a six-order linear dispersion relation of magnetized waves that contains effects due to electron and ion inertia, finite plasma beta and angular dependence of phase speed. We investigate propagation characteristics of these magnetized waves in a regime where scale lengths are comparable with electron and ion inertial length scales. This regime corresponds essentially to the solar wind plasma, where length scales, comparable with ion cyclotron frequency, lead to dispersive effects. These scales in conjunction with linear waves present a great deal of challenges in understanding the high-frequency, small-scale dynamics of turbulent fluctuations in the solar wind plasma.

scholarly journals The spectrum of small-scale density fluctuations in the solar wind

1978 ◽  
Vol 185 (2) ◽  
pp. 207-226 ◽  
Author(s):  
A. C. S. Readhead ◽  
M. C. Kemp ◽  
A. Hewish
Keyword(s):  
Solar Wind ◽  
Density Fluctuations ◽  
Small Scale

scholarly journals Sonification of Astronomical Data

2011 ◽  
Vol 7 (S285) ◽  
pp. 133-136 ◽  
Author(s):  
Wanda L. Diaz-Merced ◽  
Robert M. Candey ◽  
Nancy Brickhouse ◽  
Matthew Schneps ◽  
John C. Mannone ◽  
...  
Keyword(s):  
Solar Wind ◽  
Time Series Data ◽  
Solar Wind Plasma ◽  
Series Data ◽  
Astronomical Data ◽  
X Ray ◽  
The Earth ◽  
Polar Type ◽  
Mass Ejection ◽  
The Impact

AbstractThis document presents Java-based software called xSonify that uses a sonification technique (the adaptation of sound to convey information) to promote discovery in astronomical data. The prototype is designed to analyze two-dimensional data, such as time-series data. We demonstrate the utility of the sonification technique with examples applied to X-ray astronomy and solar data. We have identified frequencies in the Chandra X-Ray observations of EX Hya, a cataclysmic variable of the intermediate polar type. In another example we study the impact of a major solar flare, with its associated coronal mass ejection (CME), on the solar wind plasma (in particular the solar wind between the Sun and the Earth), and the Earth's magnetosphere.

scholarly journals Turbulent spectra in the solar wind plasma

2009 ◽  
Vol 76 (2) ◽  
pp. 183-191 ◽  
Author(s):  
DASTGEER SHAIKH ◽  
G. P. ZANK
Keyword(s):  
Solar Wind ◽  
Three Dimensional ◽  
Solar Wind Plasma ◽  
Density Fluctuations ◽  
Magnetized Plasma ◽  
Density Spectrum ◽  
Turbulent Spectrum ◽  
Extended Length ◽  
Turbulent Spectra ◽  
Magnetohydrodynamic Fluid

AbstractObservations of interstellar scintillations at radio wavelengths reveal a Kolmogorov-like scaling of the electron density spectrum with a spectral slope of −5/3 over six decades in wavenumber space. A similar turbulent density spectrum in the solar wind plasma has been reported. The energy transfer process in the magnetized solar wind plasma over such extended length scales remains an unresolved paradox of modern turbulence theories, raising the especially intriguing question of how a compressible magnetized solar wind exhibits a turbulent spectrum that is a characteristic of an incompressible hydrodynamic fluid. To address these questions, we have undertaken three-dimensional time-dependent numerical simulations of a compressible magnetohydrodynamic fluid describing super-Alfvénic, supersonic and strongly magnetized plasma. It is shown that the observed Kolmogorov-like (−5/3) spectrum can develop in the solar wind plasma by supersonic plasma motions that dissipate into highly subsonic motion that passively convect density fluctuations.

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