Spectral properties of electromagnetic turbulence in plasmas

D. Shaikh, P.K. Shukla

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

We report on the nonlinear turbulent processes associated with electromagnetic waves in plasmas. We focus on low-frequency (in comparison with the electron gyrofrequency) nonlinearly interacting electron whistlers and nonlinearly interacting Hall-magnetohydrodynamic (H-MHD) fluctuations in a magnetized plasma. Nonlinear whistler mode turbulence study in a magnetized plasma involves incompressible electrons and immobile ions. Two-dimensional turbulent interactions and subsequent energy cascades are critically influenced by the electron whisters that behave distinctly for scales smaller and larger than the electron skin depth. It is found that in whistler mode turbulence there results a dual cascade primarily due to the forward spectral migration of energy that coexists with a backward spectral transfer of mean squared magnetic potential. Finally, inclusion of the ion dynamics, resulting from a two fluid description of the H-MHD plasma, leads to several interesting results that are typically observed in the solar wind plasma. Particularly in the solar wind, the high-time-resolution databases identify a spectral break at the end of the MHD inertial range spectrum that corresponds to a high-frequency regime. In the latter, turbulent cascades cannot be explained by the usual MHD model and a finite frequency effect (in comparison with the ion gyrofrequency) arising from the ion inertia is essentially included to discern the dynamics of the smaller length scales (in comparison with the ion skin depth). This leads to a nonlinear H-MHD model, which is presented in this paper. With the help of our 3-D H-MHD code, we find that the characteristic turbulent interactions in the high-frequency regime evolve typically on kinetic-Alfven time-scales. The turbulent fluctuation associated with kinetic-Alfven interactions are compressive and anisotropic and possess equipartition of the kinetic and magnetic energies.
LanguageEnglish
Pages189-196
Number of pages7
JournalNonlinear Processes in Geophysics
Volume16
Issue number2
DOIs
Publication statusPublished - 12 Mar 2009

Fingerprint

Magnetohydrodynamics
magnetohydrodynamics
Turbulence
turbulence
electromagnetism
Plasmas
plasma
electron
Ions
ion
gyrofrequency
cascades
Electrons
ions
Solar wind
electrons
kinetics
solar wind
skin
Kinetics

Keywords

  • magnetohydrodynamic turbulance
  • electron magnetohydrodynamics
  • magnetic reconnection
  • power spectra
  • dissipation
  • excitation
  • whistlers
  • waves

Cite this

Shaikh, D. ; Shukla, P.K. / Spectral properties of electromagnetic turbulence in plasmas. In: Nonlinear Processes in Geophysics . 2009 ; Vol. 16, No. 2. pp. 189-196.
@article{987c247d626e4fb3999fbcab42385625,
title = "Spectral properties of electromagnetic turbulence in plasmas",
abstract = "We report on the nonlinear turbulent processes associated with electromagnetic waves in plasmas. We focus on low-frequency (in comparison with the electron gyrofrequency) nonlinearly interacting electron whistlers and nonlinearly interacting Hall-magnetohydrodynamic (H-MHD) fluctuations in a magnetized plasma. Nonlinear whistler mode turbulence study in a magnetized plasma involves incompressible electrons and immobile ions. Two-dimensional turbulent interactions and subsequent energy cascades are critically influenced by the electron whisters that behave distinctly for scales smaller and larger than the electron skin depth. It is found that in whistler mode turbulence there results a dual cascade primarily due to the forward spectral migration of energy that coexists with a backward spectral transfer of mean squared magnetic potential. Finally, inclusion of the ion dynamics, resulting from a two fluid description of the H-MHD plasma, leads to several interesting results that are typically observed in the solar wind plasma. Particularly in the solar wind, the high-time-resolution databases identify a spectral break at the end of the MHD inertial range spectrum that corresponds to a high-frequency regime. In the latter, turbulent cascades cannot be explained by the usual MHD model and a finite frequency effect (in comparison with the ion gyrofrequency) arising from the ion inertia is essentially included to discern the dynamics of the smaller length scales (in comparison with the ion skin depth). This leads to a nonlinear H-MHD model, which is presented in this paper. With the help of our 3-D H-MHD code, we find that the characteristic turbulent interactions in the high-frequency regime evolve typically on kinetic-Alfven time-scales. The turbulent fluctuation associated with kinetic-Alfven interactions are compressive and anisotropic and possess equipartition of the kinetic and magnetic energies.",
keywords = "magnetohydrodynamic turbulance, electron magnetohydrodynamics, magnetic reconnection, power spectra, dissipation, excitation, whistlers, waves",
author = "D. Shaikh and P.K. Shukla",
year = "2009",
month = "3",
day = "12",
doi = "10.5194/npg-16-189-2009",
language = "English",
volume = "16",
pages = "189--196",
journal = "Nonlinear Processes in Geophysics",
issn = "1023-5809",
number = "2",

}

Spectral properties of electromagnetic turbulence in plasmas. / Shaikh, D.; Shukla, P.K.

In: Nonlinear Processes in Geophysics , Vol. 16, No. 2, 12.03.2009, p. 189-196.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Spectral properties of electromagnetic turbulence in plasmas

AU - Shaikh, D.

AU - Shukla, P.K.

PY - 2009/3/12

Y1 - 2009/3/12

N2 - We report on the nonlinear turbulent processes associated with electromagnetic waves in plasmas. We focus on low-frequency (in comparison with the electron gyrofrequency) nonlinearly interacting electron whistlers and nonlinearly interacting Hall-magnetohydrodynamic (H-MHD) fluctuations in a magnetized plasma. Nonlinear whistler mode turbulence study in a magnetized plasma involves incompressible electrons and immobile ions. Two-dimensional turbulent interactions and subsequent energy cascades are critically influenced by the electron whisters that behave distinctly for scales smaller and larger than the electron skin depth. It is found that in whistler mode turbulence there results a dual cascade primarily due to the forward spectral migration of energy that coexists with a backward spectral transfer of mean squared magnetic potential. Finally, inclusion of the ion dynamics, resulting from a two fluid description of the H-MHD plasma, leads to several interesting results that are typically observed in the solar wind plasma. Particularly in the solar wind, the high-time-resolution databases identify a spectral break at the end of the MHD inertial range spectrum that corresponds to a high-frequency regime. In the latter, turbulent cascades cannot be explained by the usual MHD model and a finite frequency effect (in comparison with the ion gyrofrequency) arising from the ion inertia is essentially included to discern the dynamics of the smaller length scales (in comparison with the ion skin depth). This leads to a nonlinear H-MHD model, which is presented in this paper. With the help of our 3-D H-MHD code, we find that the characteristic turbulent interactions in the high-frequency regime evolve typically on kinetic-Alfven time-scales. The turbulent fluctuation associated with kinetic-Alfven interactions are compressive and anisotropic and possess equipartition of the kinetic and magnetic energies.

AB - We report on the nonlinear turbulent processes associated with electromagnetic waves in plasmas. We focus on low-frequency (in comparison with the electron gyrofrequency) nonlinearly interacting electron whistlers and nonlinearly interacting Hall-magnetohydrodynamic (H-MHD) fluctuations in a magnetized plasma. Nonlinear whistler mode turbulence study in a magnetized plasma involves incompressible electrons and immobile ions. Two-dimensional turbulent interactions and subsequent energy cascades are critically influenced by the electron whisters that behave distinctly for scales smaller and larger than the electron skin depth. It is found that in whistler mode turbulence there results a dual cascade primarily due to the forward spectral migration of energy that coexists with a backward spectral transfer of mean squared magnetic potential. Finally, inclusion of the ion dynamics, resulting from a two fluid description of the H-MHD plasma, leads to several interesting results that are typically observed in the solar wind plasma. Particularly in the solar wind, the high-time-resolution databases identify a spectral break at the end of the MHD inertial range spectrum that corresponds to a high-frequency regime. In the latter, turbulent cascades cannot be explained by the usual MHD model and a finite frequency effect (in comparison with the ion gyrofrequency) arising from the ion inertia is essentially included to discern the dynamics of the smaller length scales (in comparison with the ion skin depth). This leads to a nonlinear H-MHD model, which is presented in this paper. With the help of our 3-D H-MHD code, we find that the characteristic turbulent interactions in the high-frequency regime evolve typically on kinetic-Alfven time-scales. The turbulent fluctuation associated with kinetic-Alfven interactions are compressive and anisotropic and possess equipartition of the kinetic and magnetic energies.

KW - magnetohydrodynamic turbulance

KW - electron magnetohydrodynamics

KW - magnetic reconnection

KW - power spectra

KW - dissipation

KW - excitation

KW - whistlers

KW - waves

U2 - 10.5194/npg-16-189-2009

DO - 10.5194/npg-16-189-2009

M3 - Article

VL - 16

SP - 189

EP - 196

JO - Nonlinear Processes in Geophysics

T2 - Nonlinear Processes in Geophysics

JF - Nonlinear Processes in Geophysics

SN - 1023-5809

IS - 2

ER -