Small Scale Processes in the Solar Wind

Greco, A.; Valentini, F.; Servidio, S.

doi:10.5772/36547

Cited by 4 publications

(7 citation statements)

References 76 publications

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“…The properties of stationary and homogeneous kinetic turbulence leading to localized magnetic reconnection were numerically investigated using hybrid-PIC (Particle-in-Cell), gyrokinetic or Vlasov codes simulations [49][50][51][52][53][54][55][56][57][58]. These investigations showed that ion-scale CSs, where magnetic reconnection can take place, can form from decaying or driven turbulence, leading to heating, temperature anisotropies and dissipation.…”

Section: Introductionmentioning

confidence: 99%

Kinetic turbulence in fast three-dimensional collisionless guide-field magnetic reconnection

Muñoz

Büchner

2018

Phys. Rev. E

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Although turbulence has been conjectured to be important for magnetic reconnection, still very little is known about its role in collisionless plasmas. Previous attempts to quantify the effect of turbulence on reconnection usually prescribed Alfvénic or other low-frequency fluctuations or investigated collisionless kinetic effects in just two-dimensional configurations and antiparallel magnetic fields. In view of this, we analyzed the kinetic turbulence self-generated by three-dimensional guidefield reconnection through force-free current sheets in frequency and wavenumber spaces, utilizing 3D particle-in-cell code numerical simulations. Our investigations reveal reconnection rates and kinetic turbulence with features similar to those obtained by current in-situ spacecraft observations of MMS as well as in the laboratory reconnection experiments MRX, VTF and Vineta-II. In particular we found that the kinetic turbulence developing in the course of 3D guide-field reconnection exhibits a broadband power-law spectrum extending beyond the lower-hybrid frequency and up to the electron frequencies. In the frequency space the spectral index of the turbulence appeared to be close to -2.8 at the reconnection X-line. In the wavenumber space it also becomes -2.8 as soon as the normalized reconnection rate reaches 0.1. The broadband kinetic turbulence is mainly due to current-streaming and electron-flow-shear instabilities excited in the sufficiently thin current sheets of kinetic reconnection. The growth of the kinetic turbulence corresponds to high reconnection rates which exceed those of fast laminar, non-turbulent reconnection.

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Section: Introductionmentioning

confidence: 99%

Kinetic turbulence in fast three-dimensional collisionless guide-field magnetic reconnection

Muñoz

Büchner

2018

Phys. Rev. E

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“…Indeed, strong fluctuations are found near the same extreme regions of the β p , R p -plane where the instability growth rates are large, causing the plasma to remain (marginally) unstable to temperature-anisotropy instabilities [11,17,18]. Similarly, computations of sheardriven turbulence [19] have shown that local instabilities can sporadically arise due to kinetic effects that are inevitably found near current sheets and vortices [20,21]. From these studies, it is evident that regions contributing to strong intermittency are also regions of strong kinetic activity, and furthermore these are often juxtaposed.…”

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confidence: 99%

“…Some authors adopt the interpretation that the ion-driven microinstabilities may "feed" strong fluctuations [11] in regions of instability, materially impacting the plasma dynamics. A different point of view is that turbulence-cascade generated localized inhomogeneities, i.e, coherent structures such as current sheets [12,13], drive the temperatureanisotropies to extreme values, setting the stage for linear instabilities that might occur in regions of strong nonlinear effects.…”

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confidence: 99%

“…Turbulence, on the other hand, is an intrinsically nonlinear process. Thin current sheets, and other coherent structures generated by the energy cascade, are sites of extreme temperature anisotropy [20] and therefore, the high growth rates due to the microinstabilities also reside in the same vicinity. It is therefore not a priori obvious whether the presence of intermittency and coherent structures favors or disfavors instabilities in comparison with nonlinear effects.…”

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confidence: 99%

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Interplay of Turbulence and Proton-Microinstability Growth in Space Plasmas

Bandyopadhyay¹,

Qudsi²,

Matthaeus³

et al. 2020

Preprint

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Both kinetic instabilities and strong turbulence have potential to impact the behavior of space plasmas. To assess effects of these two processes we compare results from a 3 dimensional particle-incell (PIC) simulation of collisionless plasma turbulence against observations by the MMS spacecraft in the terrestrial magnetosheath and by the Wind spacecraft in the solar wind. The simulation develops coherent structures and anisotropic ion velocity distributions that can drive micro-instabilities. Temperature-anisotropy driven instability growth rates are compared with inverse nonlinear turbulence time scales. Large growth rates occur near coherent structures; nevertheless linear growth rates are, on average, substantially less than the corresponding nonlinear rates. This result casts some doubt on the usual basis for employing linear instability theory, and raises questions as to why the linear theory appears to work in limiting plasma excursions in anisotropy and plasma beta.

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“…However, additional magnetic field fluctuations generated in the vicinity of the z = 0 (where B x = 0) plane by plasma flows from the reconnection region [15] can significantly change the particle trajectories. Moreover, CSs can be formed within turbulent plasma flows, where magnetic field fluctuations are intrinsic property of CSs [16,17]. In this paper, we describe particle motion in a turbulent CS.…”

Section: Introductionmentioning

confidence: 99%

Charged particle dynamics in turbulent current sheets

et al. 2016

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We study dynamics of charged particle in current sheets with magnetic fluctuations. We use the adiabatic theory to describe the nonperturbed charged particle motion and show that magnetic field fluctuations destroy the adiabatic invariant. We demonstrate that the evolution of particle adiabatic invariant's distribution is described by a diffusion equation and derive analytical estimates of the rate of adiabatic invariant's diffusion. This rate is proportional to power density of magnetic field fluctuations. We compare analytical estimates with numerical simulations. We show that adiabatic invariant diffusion results in transient particles trapping in the current sheet. For magnetic field fluctuation amplitude few times larger than a normal magnetic field component, more than 50% of transient particles become trapped. We discuss the possible consequences of destruction of adiabaticity of the charged particle motion on the state of the current sheets.

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Small Scale Processes in the Solar Wind

Cited by 4 publications

References 76 publications

Kinetic turbulence in fast three-dimensional collisionless guide-field magnetic reconnection

Kinetic turbulence in fast three-dimensional collisionless guide-field magnetic reconnection

Interplay of Turbulence and Proton-Microinstability Growth in Space Plasmas

Charged particle dynamics in turbulent current sheets

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