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434 results on '"Sahraoui, F."'

153. A comparison of wave mode identification techniques

Author

Walker, S.N.F., Sahraoui, F., Balikhin, M.A., Belmont, G., Pincon, J.L., Rezeau, L., Alleyne, H., Cornilleau-Wehrlin, N., André, Mats, Walker, S.N.F., Sahraoui, F., Balikhin, M.A., Belmont, G., Pincon, J.L., Rezeau, L., Alleyne, H., Cornilleau-Wehrlin, N., and André, Mats

Published
2004

185. The Magnetosheath

Author

Lucek, E. A., primary, Constantinescu, D., additional, Goldstein, M. L., additional, Pickett, J., additional, Pinçon, J. L., additional, Sahraoui, F., additional, Treumann, R. A., additional, and Walker, S. N., additional

Published
2005
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186. A comparison of wave mode identification techniques

Author

Walker, S. N., primary, Sahraoui, F., additional, Balikhin, M. A., additional, Belmont, G., additional, Pinçon, J. L., additional, Rezeau, L., additional, Alleyne, H., additional, Cornilleau-Wehrlin, N., additional, and André, M., additional

Published
2004
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190. Electron Scale Solar Wind Turbulence: Cluster Observations and Theoretical Modeling.

Author

Sahraoui, F. and Goldstein, M. L.

Subjects
*SOLAR wind, *TURBULENCE, *ASTRONOMICAL observations, *MAGNETOHYDRODYNAMICS, *SPACE vehicles, *COSMIC magnetic fields, *DATA analysis, *MATHEMATICAL models
Abstract

Turbulence at MagnetoHydroDynamics (MHD) scales of the solar wind has been studied for more than three decades, using data analyzes, theoretical and numerical modeling. However smaller scales have not been explored until very recently. Here, we review recent results on the first observation of cascade and dissipation of the solar wind turbulence at the electron scales. Thanks to the high resolution magnetic and electric field data of the Cluster spacecraft, we computed the spectra of turbulence up to ∼100 Hz (in the spacecraft reference frame) and found two distinct breakpoints in the magnetic spectrum at 0.4 Hz and 35 Hz, which correspond, respectively, to the Doppler-shifted proton and electron gyroscales, ƒρp and ƒρe. Below ƒρp the spectrum follows a Kolmogorov scaling ƒ-1.62, typical of spectra observed at 1 AU. Above ƒρp a second inertial range is formed with a scaling ƒ-2.3 down to ƒρe. Above ƒρe the spectrum has a steeper power law ∼ƒ-4.1 down to the noise level of the instrument. Solving numerically the linear Maxwell-Vlasov equations combined with recent theoretical predictions of the Gyro-Kinetic theory, we show that the present results are fully consistent with a scenario of a quasi-two-dimensional cascade into Kinetic Alfvén modes (KAW). [ABSTRACT FROM AUTHOR]

Published
2011
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195. Topology of Magnetic and Velocity Fields at Kinetic Scales in Incompressible Plasma Turbulence

Author

Zhang, J., Huang, S. Y., Sahraoui, F., Andrés, N., Yuan, Z. G., Jiang, K., Xu, S. B., Wei, Y. Y., Xiong, Q. Y., Wang, Z., Lin, R. T., and Yu, L.

Abstract

The topology of the magnetic and velocity fields at the kinetic scales are investigated in the context of nearly incompressible magnetosheath plasma turbulence. Using the unprecedented high‐resolution data from the Magnetospheric MultiScale mission, the joint probability distribution functions of geometrical invariants characterizing the magnetic and velocity fields gradient tensor at the kinetic scales are computed. The topological features of the magnetic and velocity field gradient tensors and their symmetric component tensors present axisymmetric distribution patterns, indicating that the structure of the plasma turbulence at the kinetic scales are different from those in hydrodynamic and magnetohydrodynamic turbulence. Moreover, a strong correlation between the straining and rotational parts of the magnetic and velocity field gradient tensors was found, which manifests the dominance of sheet‐like structures at the kinetic‐scales dissipation in incompressible plasma turbulence. The terrestrial magnetosheath provides an excellent laboratory to study space plasma turbulence. Thanks to the unprecedented high time resolution data of the Magnetospheric Multiscale mission, the kinetic‐scales structures and dynamic of incompressible magnetosheath plasma turbulence can be investigated. By means of a universal topological classification method in fluid dynamics area, we construct the topological features of both magnetic and velocity field in incompressible plasma turbulence at dissipation scales. Our results show that the distribution of velocity‐field topological structures is different from the other turbulence system, such as hydrodynamic and magnetohydrodynamic turbulence. In addition, we verify that the sheet‐like structures dominate the kinetic‐scales dissipation in the incompressible plasma turbulence. The kinetic‐scales topological features in incompressible magnetosheath plasma turbulence are investigatedDistribution patterns different from hydrodynamic and magnetohydrodynamic turbulence of velocity‐field topological characteristics are identifiedSheet‐like structures dominate dissipation‐scale dynamics in the incompressible plasma turbulence The kinetic‐scales topological features in incompressible magnetosheath plasma turbulence are investigated Distribution patterns different from hydrodynamic and magnetohydrodynamic turbulence of velocity‐field topological characteristics are identified Sheet‐like structures dominate dissipation‐scale dynamics in the incompressible plasma turbulence

Published
2023
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197. A case study of low-frequency waves at the magnetopause

Author

Rezeau, L., primary, Sahraoui, F., additional, d’Humières, E., additional, Belmont, G., additional, Chust, T., additional, Cornilleau-Wehrlin, N., additional, Mellul, L., additional, Alexandrova, O., additional, Lucek, E., additional, Robert, P., additional, Décréau, P., additional, Canu, P., additional, and Dandouras, I., additional

Published
2001
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200. Observations of Kolmogorov Turbulence in Saturn's Magnetosphere.

Author

Xu, S. B., Huang, S. Y., Sahraoui, F., Yuan, Z. G., Wu, H. H., Jiang, K., Zhang, J., and Lin, R. T.

Subjects
*SOLAR wind, *MAGNETOSPHERE, *SATURN (Planet), *TURBULENCE, *PLASMA astrophysics, *ELECTRON density, *PLASMA turbulence, *MAGNETOHYDRODYNAMIC instabilities
Abstract

The Kolmogorov scaling in the inertial range of scales is a distinct characteristic of fully developed turbulence, and studying it offers valuable insights into the evolution of turbulence. In this work, we perform a statistical survey of the power spectra with the Kolmogorov scaling in Saturn's magnetosphere using Cassini measurements. Two cases study show that both magnetic‐field and electron density spectra exhibit f−5/3 at the MHD scales. The statistical analysis reveals a wide‐ranging and abundant presence of Kolmogorov spectra throughout magnetosphere, observed across all local times. Interestingly, the occurrence rate of these Kolmogorov‐like events within Saturn's magnetosphere surpasses that observed in the planetary magnetosheath. The measurements of magnetic compressibility for the Kolmogorov‐like events show the dominance of incompressible Alfvénic turbulence (44.64%) with respect to magnetosonic‐like one (6.94%). In addition, the source and evolution of the turbulent fluctuations are further discussed. Plain Language Summary: Turbulence is ubiquitous in space and astrophysical plasmas, such as the solar wind, planetary magnetospheres, and the interstellar medium. Plasma turbulence has been widely studied in the solar wind and planetary magnetosheaths, but much less in the planetary magnetospheres. In the solar wind, power spectral density of the magnetic field fluctuations generally follows the so‐called Kolmogorov spectrum f−5/3 at the magnetohydrodynamic (MHD) scales, which suggests a fully developed turbulent state. In this study, we have discovered the widespread presence of Kolmogorov spectra in the Saturn's magnetosphere. The spatial distribution and nature of turbulent fluctuation for the Kolmogorov‐like events are also investigated in detail. Key Points: Magnetic field and electron density spectra have Kolmogorov scaling of f−5/3 at MHD scales in Saturn's magnetosphereThe spatial distribution of the Kolmogorov spectra within Saturn's magnetosphere reveals the extensive occurrence of Kolmogorov‐like eventsThe fluctuations for Kolmogorov‐like events are dominated by Alfvénic modes (44.64%) with respect to magnetosonic‐like one (6.94%) [ABSTRACT FROM AUTHOR]

Published
2023
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