Nonlinear propagation of whistler wave and turbulent spectrum in reconnection region of magnetopause

Sharma, R. P.; Pathak, Neha; Yadav, Nitin; Sharma, Prachi

doi:10.1063/1.4998475

“…Whistler mode waves have received much attention in reconnection studies. They have been suggested to facilitate the reconnection process (Deng & Matsumoto, ; Drake et al, ; Mandt et al, ), to modulate the reconnection rate (Goldman et al, ), and to accelerate electrons near the magnetopause boundary (Jaynes et al, ; Sharma et al, ). In addition, the standing oblique electrostatic whistler waves near the electron diffusion region edge may cause local dissipation (Burch, Ergun, et al, ).…”

Section: Introductionmentioning

confidence: 99%

Local Excitation of Whistler Mode Waves and Associated Langmuir Waves at Dayside Reconnection Regions

Li

¹

,

Bortnik

²

,

An

³

et al. 2018

Geophysical Research Letters

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In the Earth's dayside reconnection boundary layer, whistler mode waves coincide with magnetic field openings and the formation of the resultant anisotropic electrons. Depending on the energy range of anisotropic electrons, whistlers can grow at frequencies in the upper and/or lower band. Observations show that whistler mode waves modulate Langmuir wave amplitude as they propagate toward the X line. Observations of whistler mode wave phase and Langmuir waves packets, as well as coincident electron measurements, reveal that whistler mode waves can accelerate electrons via Landau resonance at locations where E||is antiparallel to the wave propagation direction. The accelerated electrons produce localized beams, which subsequently drive the periodically modulated Langmuir waves. The close association of those two wave modes reveals the microscale electron dynamics in the exhaust region, and the proposed mechanism could potentially be applied to explain the modulation events observed in planetary magnetospheres and in the solar wind.

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“…There is no single clear physical mechanism which produces the small scale fluctuations leading to plasma heating. It may be due to KAWs or whistler waves, or the interactions between them (Gary & Smith 2009;Salem et al 2012;Boldyrev et al 2013;Chen et al 2013a,b) or interactions of KAWs with ion acoustic or magnetosonic waves (Sharma et al 2017). Therefore, the KAW propagation in the modified background density due to ponderomotive force and Joule heating, as we discussed here, leading to the transverse collapse of magnetic coherent structures may be one of the possible physical processes to explain the heating in coronal loops.…”

Section: Introductionmentioning

confidence: 61%

“…However, the origin of small scale fluctuations is not understood well, which may be due to whistler waves or KAWs, or the interactions between them (Gary & Smith 2009;Salem et al 2012;Boldyrev et al 2013;Chen et al 2013a,b) or interactions of KAWs with ion acoustic and magnetosonic waves. Sharma et al (2017) also studied coronal heating by considering the localization of slow magnetosonic waves due to the background density perturbation. In spite of all these mechanisms, there is still no consensus theory to explain the coronal heating by turbulence.…”

Section: Numerical Simulation and Resultsmentioning

confidence: 99%

Anisotropic turbulence of kinetic Alfvén waves and heating in solar corona

Singh

¹

,

Jatav

²

2019

Res. Astron. Astrophys.

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Understanding solar coronal heating has been one of the unresolved problems in solar physics in spite of the many theories that have been developed to explain it. Past observational studies suggested that kinetic Alfvén waves (KAWs) may be responsible for solar coronal heating by accelerating the charged particles in solar plasma. In this paper, we investigated the transient dynamics of KAWs with modified background density due to ponderomotive force and Joule heating. A numerical simulation based on pseudo-spectral method was applied to study the evolution of KAW magnetic coherent structures and generation of magnetic turbulence. Using different initial conditions in simulations, the dependence of KAW dynamics on the nature of inhomogeneous solar plasma was thoroughly investigated. The saturated magnetic power spectra follow Kolmogorov scaling of k −5/3 in the inertial range, then followed by steep anisotropic scaling in the dissipation range. The KAW has anisotropy of k ∥ ∝ k ⊥ 0.53 , k ∥ ∝ k ⊥ 0.50 , k ∥ ∝ k ⊥ 0.83 and k ∥ ∝ k ⊥ 0.30 depending on the kind of initial conditions of inhomogeneity. The power spectra of magnetic field fluctuations showing the spectral anisotropy in wavenumber space indicate that the nonlinear interactions may be redistributing the energy anisotropically among higher modes of the wavenumber. Therefore, anisotropic turbulence can be considered as one of the candidates responsible for the particle energization and heating of the solar plasmas.

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“…We have also assumed the propagation of 3D whistler wave with the wave vector

\overset{k}{true} = k_{x} \overset{x}{true} + k_{y} \overset{y}{true} + k_{z} \overset{z}{true}

in magnetized plasma with a magnetic field

{\overset{true\to}{B}}_{0} = B_{0 z} \overset{z}{true} + B_{0 y} \overset{y}{true}

. Making use of Electron Magnetohydrodynamics (EMHD) model based on basic equations, viz., Faraday law, generalized Ohm's law, and Ampere's law, we obtain the dynamical equation of whistler wave in the presence of Harris sheet (Sharma et al, )

\begin{matrix} lefttrue \\ \frac{\partial^{2} {\overset{A}{true}}_{z}}{\partial t^{2}} + λ_{e}^{4} \frac{\partial^{6} {\overset{A}{true}}_{z}}{\partial t^{2} \partial x^{4}} + λ_{e}^{4} \frac{\partial^{6} {\overset{A}{true}}_{z}}{\partial t^{2} \partial y^{4}} + λ_{e}^{4} \frac{\partial^{6} {\overset{A}{true}}_{z}}{\partial t^{2} \partial z^{4}} + 2 λ_{e}^{4} \nabla_{⊥}^{2} \frac{\partial^{4} {\overset{A}{true}}_{z}}{\partial t^{2} \partial z^{2}} - 2 λ_{e}^{2} \frac{\partial^{2}}{\partial t^{2}} (\nabla_{⊥}^{2} + \frac{\partial^{2}}{\partial z^{2}}) {\overset{A}{true}}_{z} + \\ λ_{i}^{2} v_{A}^{2} \frac{\partial^{4} {\overset{A}{true}}_{z}}{\partial z^{4}} + \frac{λ_{i}^{2} B_{0 y}^{2}}{4 π n_{0} m_{i}} \nabla_{⊥}^{2} \partial^{2} <...> \end{matrix}

…”

Section: Basic Formulationmentioning

confidence: 99%

Localized Structures and Turbulent Spectra in the Magnetopause

Pathak

¹

,

Uma

²

,

Sharma

³

2019

JGR Space Physics

Self Cite

3

0

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Kinetic Alfvén wave (KAW) and whistler wave play a key role in the framework of turbulence and reconnection. There are lot of observations of these wave in the magnetopause region. The present paper deals with the nonlinear evolution of KAW and a weak whistler wave through the preexisting magnetic reconnection site. For this study the dynamical evolution equations are derived by taking into account the ponderomotive force driven density modification and magnetic field fluctuations due to shear field modeled by the Harris sheet. Furthermore, these equations have been solved numerically as well as semianalytically. For numerical integrations we have used the pseudospectral method and finite difference method and for semianalytically Runge Kutta method. Simulated results have shown the evolution of coherent structures or current sheets, which are capable to energy transfer efficiently. These structures have scale size around ion gyroradius as well as electron inertial length as calculated analytically. At a later time the chaotic structures arise in this reconnection site. This gives the signature of turbulence generation. Therefore, the magnetic power spectrum with scaling is also presented in this manuscript and their relevance with the observed spectrum (calculated from the Cluster data (Chaston,

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Nonlinear propagation of whistler wave and turbulent spectrum in reconnection region of magnetopause

Cited by 8 publications

References 53 publications

Local Excitation of Whistler Mode Waves and Associated Langmuir Waves at Dayside Reconnection Regions

Local Excitation of Whistler Mode Waves and Associated Langmuir Waves at Dayside Reconnection Regions

Anisotropic turbulence of kinetic Alfvén waves and heating in solar corona

Localized Structures and Turbulent Spectra in the Magnetopause

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