Kinetic Plasma Turbulence Generated in a 3D Current Sheet With Magnetic Islands

In this article we aim to investigate the kinetic turbulence in a reconnecting current sheet (RCS) with X- and O-nullpoints and to explore its link to the features of accelerated particles. We carry out simulations of magnetic reconnection in a thin current sheet with 3D magnetic field topology affe...

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Autores principales:	Valentina Zharkova, Qian Xia
Formato:	article
Lenguaje:	EN
Publicado:	Frontiers Media S.A. 2021
Materias:	particle acceleration magnetic reconnection plasma methods: numerical beam instability kinetic turbulence Astronomy QB1-991 Geophysics. Cosmic physics QC801-809
Acceso en línea:	https://doaj.org/article/2d74b1e67c08478ea7d0ad30fcb4031c
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spelling	oai:doaj.org-article:2d74b1e67c08478ea7d0ad30fcb4031c2021-12-01T09:07:10ZKinetic Plasma Turbulence Generated in a 3D Current Sheet With Magnetic Islands2296-987X10.3389/fspas.2021.665998https://doaj.org/article/2d74b1e67c08478ea7d0ad30fcb4031c2021-11-01T00:00:00Zhttps://www.frontiersin.org/articles/10.3389/fspas.2021.665998/fullhttps://doaj.org/toc/2296-987XIn this article we aim to investigate the kinetic turbulence in a reconnecting current sheet (RCS) with X- and O-nullpoints and to explore its link to the features of accelerated particles. We carry out simulations of magnetic reconnection in a thin current sheet with 3D magnetic field topology affected by tearing instability until the formation of two large magnetic islands using particle-in-cell (PIC) approach. The model utilizes a strong guiding field that leads to the separation of the particles of opposite charges, the generation of a strong polarization electric field across the RCS, and suppression of kink instability in the “out-of-plane” direction. The accelerated particles of the same charge entering an RCS from the opposite edges are shown accelerated to different energies forming the “bump-in-tail” velocity distributions that, in turn, can generate plasma turbulence in different locations. The turbulence-generated waves produced by either electron or proton beams can be identified from the energy spectra of electromagnetic field fluctuations in the phase and frequency domains. From the phase space analysis we gather that the kinetic turbulence may be generated by accelerated particle beams, which are later found to evolve into a phase-space hole indicating the beam breakage. This happens at some distance from the particle entrance into an RCS, e.g. about 7di (ion inertial depth) for the electron beam and 12di for the proton beam. In a wavenumber space the spectral index of the power spectrum of the turbulent magnetic field near the ion inertial length is found to be −2.7 that is consistent with other estimations. The collective turbulence power spectra are consistent with the high-frequency fluctuations of perpendicular electric field, or upper hybrid waves, to occur in a vicinity of X-nullpoints, where the Langmuir (LW) can be generated by accelerated electrons with high growth rates, while further from X-nullponts or on the edges of magnetic islands, where electrons become ejected and start moving across the magnetic field lines, Bernstein waves can be generated. The frequency spectra of high- and low-frequency waves are explored in the kinetic turbulence in the parallel and perpendicular directions to the local magnetic field, showing noticeable lower hybrid turbulence occurring between the electron’s gyro- and plasma frequencies seen also in the wavelet spectra. Fluctuation of the perpendicular electric field component of turbulence can be consistent with the oblique whistler waves generated on the ambient density fluctuations by intense electron beams. This study brings attention to a key role of particle acceleration in generation kinetic turbulence inside current sheets.Valentina ZharkovaQian XiaQian XiaFrontiers Media S.A.articleparticle accelerationmagnetic reconnectionplasmamethods: numericalbeam instabilitykinetic turbulenceAstronomyQB1-991Geophysics. Cosmic physicsQC801-809ENFrontiers in Astronomy and Space Sciences, Vol 8 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	particle acceleration magnetic reconnection plasma methods: numerical beam instability kinetic turbulence Astronomy QB1-991 Geophysics. Cosmic physics QC801-809
spellingShingle	particle acceleration magnetic reconnection plasma methods: numerical beam instability kinetic turbulence Astronomy QB1-991 Geophysics. Cosmic physics QC801-809 Valentina Zharkova Qian Xia Qian Xia Kinetic Plasma Turbulence Generated in a 3D Current Sheet With Magnetic Islands
description	In this article we aim to investigate the kinetic turbulence in a reconnecting current sheet (RCS) with X- and O-nullpoints and to explore its link to the features of accelerated particles. We carry out simulations of magnetic reconnection in a thin current sheet with 3D magnetic field topology affected by tearing instability until the formation of two large magnetic islands using particle-in-cell (PIC) approach. The model utilizes a strong guiding field that leads to the separation of the particles of opposite charges, the generation of a strong polarization electric field across the RCS, and suppression of kink instability in the “out-of-plane” direction. The accelerated particles of the same charge entering an RCS from the opposite edges are shown accelerated to different energies forming the “bump-in-tail” velocity distributions that, in turn, can generate plasma turbulence in different locations. The turbulence-generated waves produced by either electron or proton beams can be identified from the energy spectra of electromagnetic field fluctuations in the phase and frequency domains. From the phase space analysis we gather that the kinetic turbulence may be generated by accelerated particle beams, which are later found to evolve into a phase-space hole indicating the beam breakage. This happens at some distance from the particle entrance into an RCS, e.g. about 7di (ion inertial depth) for the electron beam and 12di for the proton beam. In a wavenumber space the spectral index of the power spectrum of the turbulent magnetic field near the ion inertial length is found to be −2.7 that is consistent with other estimations. The collective turbulence power spectra are consistent with the high-frequency fluctuations of perpendicular electric field, or upper hybrid waves, to occur in a vicinity of X-nullpoints, where the Langmuir (LW) can be generated by accelerated electrons with high growth rates, while further from X-nullponts or on the edges of magnetic islands, where electrons become ejected and start moving across the magnetic field lines, Bernstein waves can be generated. The frequency spectra of high- and low-frequency waves are explored in the kinetic turbulence in the parallel and perpendicular directions to the local magnetic field, showing noticeable lower hybrid turbulence occurring between the electron’s gyro- and plasma frequencies seen also in the wavelet spectra. Fluctuation of the perpendicular electric field component of turbulence can be consistent with the oblique whistler waves generated on the ambient density fluctuations by intense electron beams. This study brings attention to a key role of particle acceleration in generation kinetic turbulence inside current sheets.
format	article
author	Valentina Zharkova Qian Xia Qian Xia
author_facet	Valentina Zharkova Qian Xia Qian Xia
author_sort	Valentina Zharkova
title	Kinetic Plasma Turbulence Generated in a 3D Current Sheet With Magnetic Islands
title_short	Kinetic Plasma Turbulence Generated in a 3D Current Sheet With Magnetic Islands
title_full	Kinetic Plasma Turbulence Generated in a 3D Current Sheet With Magnetic Islands
title_fullStr	Kinetic Plasma Turbulence Generated in a 3D Current Sheet With Magnetic Islands
title_full_unstemmed	Kinetic Plasma Turbulence Generated in a 3D Current Sheet With Magnetic Islands
title_sort	kinetic plasma turbulence generated in a 3d current sheet with magnetic islands
publisher	Frontiers Media S.A.
publishDate	2021
url	https://doaj.org/article/2d74b1e67c08478ea7d0ad30fcb4031c
work_keys_str_mv	AT valentinazharkova kineticplasmaturbulencegeneratedina3dcurrentsheetwithmagneticislands AT qianxia kineticplasmaturbulencegeneratedina3dcurrentsheetwithmagneticislands AT qianxia kineticplasmaturbulencegeneratedina3dcurrentsheetwithmagneticislands
_version_	1718405345150238720

Kinetic Plasma Turbulence Generated in a 3D Current Sheet With Magnetic Islands

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