Theory of turbulent plasma heating by anomalous absorption of magnetosonic waves (original) (raw)
Introduction to Turbulence in Magnetised Plasmas
AIP Conference Proceedings, 2008
The ideas of turbulence of small fluctuations on a background as a statistical phenomenon are outlined. Basic properties such as three-wave interactions and spatial scale cascades are derived from the basic equations. Passive scalar dynamics is treated. The special case of dissipative coupling between the fluid and an otherwise passive scalar, of central relevance to magnetised plasmas, is used as an example.
Heat Transfer and Reconnection Diffusion in Turbulent Magnetized Plasmas
Heat Conduction - Basic Research, 2011
It is well known that magnetic fields constrain motions of charged particles, impeding the diffusion of charged particles perpendicular to magnetic field direction. This modification of transport processes is of vital importance for a wide variety of astrophysical processes including cosmic ray transport, transfer of heavy elements in the interstellar medium, star formation etc. Dealing with these processes one should keep in mind that, in realistic astrophysical conditions, magnetized fluids are turbulent. In this review we single out a particular transport process, namely, heat transfer and consider how it occurs in the presence of the magnetized turbulence. We show that the ability of magnetic field lines to constantly change topology and connectivity is at the heart of the correct description of the 3D magnetic field stochasticity in turbulent fluids. This ability is ensured by fast magnetic reconnection in turbulent fluids and puts forward the concept of reconnection diffusion at the core of the physical picture of heat transfer in astrophysical plasmas. Appealing to reconnection diffusion we describe the ability of plasma to diffuse between different magnetized eddies explaining the advection of the heat by turbulence. Adopting the structure of magnetic field that follows from the modern understanding of MHD turbulence, we also discuss thermal conductivity that arises as electrons stream along stochastic magnetic field lines. We compare the effective heat transport that arise from the two processes and conclude that, in many astrophysicallymotivated cases, eddy advection of heat dominates. Finally, we discuss the concepts of sub and superdiffusion and show that the subdiffusion requires rather restrictive settings. At the same time, accelerated diffusion or superdiffusion of heat perpendicular to the mean magnetic field direction is possible on the scales less than the injection scale of the turbulence.
A spectroscopic investigation of turbulence in magnetized plasmas
Communications in Nonlinear Science and Numerical Simulation, 2003
We present a spectroscopic investigation of turbulence in the Tore-Supra edge plasma, where deuterium spectral lines are found to exhibit a power-law behavior in their wings. Such a feature is not predicted by the equilibrium line broadening theory in the conditions of the edge plasma, where the thermal Stark effect is negligible. Therefore, the possible role of turbulence is investigated along two separate paths. Indeed, both the Stark and the Doppler profiles may differ significantly from the equilibrium profiles.
Turbulent amplification of magnetic field in laser plasma interaction and astrophysical plasmas
Physics of Plasmas, 2017
The investigation of the nonlinear evolution of magnetosonic wave (MSW) in the presence of density fluctuations at the background has been presented in this paper. The propagation of a single beam or counter propagation of beams is assumed to change the background density accordingly. The model equation for MSW has been obtained by considering the effect of modified plasma density in the background, along with the nonlinear ponderomotive force. The equation so found has been numerically solved to study its effect on the localization of MSW. From the results, the localized and filamentary structures of the MSW can be observed. The effect of variation of the amplitude of density perturbation has been studied on the amplification of magnetic field. To get better insight of these structures, a semi-analytical model with paraxial approximation has been studied. The effect of background density fluctuations on the resulting turbulent spectrum has been evaluated. The results show that the ...
Thermally driven magnetic turbulence in the presence of radiation cooling in plasmas
Journal of Plasma Physics, 1993
Instabilities of the flute-like magnetic fluctuations in the presence of radiation cooling in a non-uniform magnetoplasma are investigated. It is shown that magnetic turbulence can cause anomalous cross-field electron energy transport. The relevance of the investigation to magnetic and inertial fusion as well as to astrophysical plasmas is pointed out.
Journal of Geophysical Research, 2008
This paper studies the turbulent cascade of magnetic energy in weakly collisional magnetized plasmas. A cascade model is presented, based on the assumptions of local nonlinear energy transfer in wavenumber space, critical balance between linear propagation and nonlinear interaction times, and the applicability of linear dissipation rates for the nonlinearly turbulent plasma. The model follows the nonlinear cascade of energy from the driving scale in the MHD regime, through the transition at the ion Larmor radius into the kinetic Alfvén wave regime, in which the turbulence is dissipated by kinetic processes. The turbulent fluctuations remain at frequencies below the ion cyclotron frequency due to the strong anisotropy of the turbulent fluctuations, k ≪ k ⊥ (implied by critical balance). In this limit, the turbulence is optimally described by gyrokinetics; it is shown that the gyrokinetic approximation is well satisfied for typical slow solar wind parameters. Wave phase velocity measurements are consistent with a kinetic Alfvén wave cascade and not the onset of ion cyclotron damping. The conditions under which the gyrokinetic cascade reaches the ion cyclotron frequency are established. Cascade model solutions imply that collisionless damping provides a natural explanation for the observed range of spectral indices in the dissipation range of the solar wind. The dissipation range spectrum is predicted to be an exponential fall off; the power-law behavior apparent in observations may be an artifact of limited instrumental sensitivity. The cascade model is motivated by a programme of gyrokinetic simulations of turbulence and particle heating in the solar wind.
Magnetosonic shock waves propagating obliquely in a warm collisional plasma
Physica Scripta, 1991
The relaxed state of a slightly resistive and turbulent magnetized plasma is obtained by invoking the principle of minimum dissipation, which leads to = 3 = 3 = 3 B LB. A solution of this equation is accomplished using the analytic continuation of the Chandrasekhar-Kendall eigenfunctions in the complex domain. The new features of this theory show (i) that a single fluid can relax to an MHD equilibrium which can support a pressure gradient even without a long-term coupling between mechanical flow and magnetic field, and (ii) field reversal in states that are not force free.
Recent results on magnetic plasma turbulence
2013
Magnetic plasma turbulence is observed over a broad range of scales in the solar wind. We discuss the results of high-resolution numerical simulations of magnetohydrodynamic (MHD) turbulence that models plasma motion at large scales and the results of numerical simulations of kinetic-Alfvén turbulence that models plasma motion at small, sub-proton scales. The simulations, with numerical resolutions up to 2048 3 mesh points in the MHD case and 512 3 points in kinetic-Alfvén case and statistics accumulated over 30 to 150 eddy turnover times, constitute, to the best of our knowledge, the largest statistical sample of steadily driven three dimensional MHD and kinetic-Alfvén turbulence to date.
Theory of heating of hot magnetized plasma by Alfven waves. Application for solar corona
The heating of magnetized plasma by propagation of Alfven waves is calculated as a function of the magnetic field spectral density. The results can be applied to evaluate the heating power of the solar corona at known data from satellites' magnetometers. This heating rate can be incorporated in global models for heating of the solar corona and creation of the solar wind. The final formula for the heating power is illustrated with a model spectral density of the magnetic field obtained by analysis of the Voyager 1 mission results. The influence of high frequency dissipative modes is also taken into account and it is concluded that for evaluation of the total coronal heating it is necessary to know the spectral density of the fluctuating component of the magnetic field up to the frequency of electron-proton collisions.