Transient Evolution of Nonlinear Localized Coherent Structures of Kinetic Alfvén Waves

Abstract

We present numerical simulations of kinetic Alfvén waves (KAWs) and inertial Alfvén waves (IAWs) applicable to the solar wind, the solar corona, and the auroral regions, respectively, leading to the formation of coherent magnetic structures when the nonlinearity arises from ponderomotive effects and Joule heating. The nonlinear dynamical equation satisfies the modified nonlinear Schrödinger equation. The effect of nonlinear coupling between the main KAW/IAW and the perturbation, producing filamentary structures of the magnetic field, has been studied. Scalings in the spectral index of the power spectrum at different times have been calculated. These filamentary structures can act as a source for particle acceleration by wave -particle interaction because the KAWs/IAWs are mixed modes and Landau damping is possible.

Properties of dispersive Alfvén waves: 3. Hydrodynamics (Very Low, Intermediate, and Low Density Plasmas)

“…Using formulae (5) and expressions for the electric field polarization (13), we obtain for the magnetic field polarization (14) It can be shown from (14) that B y ӷ B x and B z . Hence, the main magnetic field component for DAWs in plasmas of very low, intermediate, and low pressure is B y .…”

“…In fact, there is an extension of the Alfvénic branch to the region of small transverse wave vectors where Alfvén waves possess specific properties. The unique ness of these properties enables one to consider Alfvén waves as one of the most promising sources of the energy transfer and particle heating in space [6,9,17,20] and as a very effective mechanism of charged particle acceleration [5,11,12,14]. It should be noted that Alfvén waves can play an important role in the formation of solar faculae [19] and spicules [18], in the magnetic field reconnection [16], in the formation of flares [4], in cometary tails [7], in the generation of convection cells [13], cavities [3], bubbles [15], etc.…”

Kinetic Alfvén wave turbulence in space plasmas

“…(11) and (12) in the time derivative of Eq. (10), the dynamical equation for nonlinear KAW [26][27][28][29][30][31][32][33] is obtained as…”

“…The approach was in paraxial regime and the scaling laws were found in the inertial range (≈ k −5/3 ). Singh and Sharma studied the spatial [27] and temporal [28] evolution of KAW/inertial Alfvén wave (IAW) with the adiabatic response of the density. They numerically solved the dynamical equation for KAW/IAW and studied the KAW/IAW turbulence via filamentation process.…”

“…The saturated spectra depend on the nonlinear process involved. In these earlier works [26][27][28] ponderomotive force of KAW has been taken into account to set up the nonlinear dynamical equation for KAW termed as MNLS equation. The ponderomotive force plays a very important role in the saturation of the magnetic spectra of KAW.…”