Inhomogeneous whistler turbulence in space plasmas

Abstract

A non‐linear two‐dimensional fluid model of whistler turbulence is developed that non‐linearly couples wave magnetic field with electron density perturbations. This coupling leads essentially to finite compressibility effects in whistler turbulence model. Interestingly it is found from our simulations that despite strong compressibility effects, the density fluctuations couple only weakly to the wave magnetic field fluctuations. In a characteristic regime where large‐scale whistlers are predominant, the weakly coupled density fluctuations do not modify inertial range energy cascade processes. Consequently, the turbulent energy is dominated by the large‐scale (compared to electron inertial length) eddies and it follows a Kolmogorov‐like k−7/3 spectrum, where k is a characteristic wavenumber. The weak coupling of the density fluctuations is explained on the basis of a whistler wave parameter that quantifies the contribution of density perturbations in the wave magnetic field.

Study of kinetic Alfvén wave and whistler wave spectra and their implication in solar wind plasma

“…For example, Shaikh [2009] describes that a magnetic spectrum of whistler turbulence has a scaling of ( k −7/3 ) at relatively large scales. Shaikh [2010] further shows that the spectral index of magnetic spectrum is weakly coupled with the density fluctuations. But in the present work, whistler magnetic field spectrum has been studied when whistler fluctuations are coupled with the density fluctuations created by KAW.…”

Nonlinear effects associated with kinetic Alfvén wave

“…However, the physical mechanisms responsible for the turbulence dissipation are still an open question, and understanding these dissipative mechanisms is an active area of research. One of the views is to interpret the spectral steepening as the evidence of kinetic Alfvén waves [ Leamon et al, ; Bale et al, ; Howes et al ., , ; Schekochihin et al, ; Howes and Quataert, ; Sahraoui et al, ; Salem et al, ] or whistler waves [ Biskamp et al, ; Li et al, ; Stawicki et al, ; Krishan and Mahajan, ; Galtier, ; Gary and Smith, ; Podesta, ; Saito et al, ; Shaikh, ] at ion kinetic scales, and an alternate view may be the presence of current sheets and Alfvén vortices at these scales which have been observed in magnetosphere and ionosphere [ Chmyrev et al, ; Volwerk et al, ; Sundkvist et al, ; Alexandrova et al, ]. Other possibilities may include ion cyclotron [ Goldstein et al, ; Leamon et al, ; Gary , ; He et al, ] and ion Bernstein waves [ Howes , ; Sahraoui et al, ].…”

Nonlinear interaction of 3D kinetic Alfvén wave and whistler wave in solar wind plasmas

“…The two leading hypotheses so as to describe the fluctuations contributing to the k-part of the turbulent spectra observed in the solar wind are that these fluctuations have the characteristics of kinetic Alfven waves [Howes and Quattaert, 2010;Leamon et al, 1998;Bale et al, 2005;Sahraoui et al, 2009] or of whistler waves [Stawicki et al, 2001;Krishan and Mahajan 2004;Galtier, 2006;Gary and Smith, 2009;Podesta et al, 2010;Saito et al, 2010;Shaikh, 2010]. It has been demonstrated by Gary et al [2008] that whistler turbulence may be responsible for the steep power law spectra, called as dispersion range.…”

“…The parametric decay of whistler wave into another whistler wave and a kinetic Alfven wave has been studied emphasizing the importance of this decay process in magnetosphere [Chen, 1977]. The stimulated Brillouin scattering of the whistler waves off the kinetic Alfven waves in plasmas has been investigated by Sharma et al [1986]. They have obtained explicit expressions for the growth rate and threshold power for this parametric process.…”