Influence of the Nonlinearity Parameter on the Solar Wind Sub-Ion Magnetic Energy Spectrum: Flr–landau Fluid Simulations

Sulem, P. L.; Passot, T.; Laveder, D.; Borgogno, Dario

doi:10.3847/0004-637x/818/1/66

Cited by 33 publications

(34 citation statements)

References 45 publications

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“…These exponents are to be compared with satellite observational data that display slopes steeper than the WWs −11/3 spectrum. Note that other physical effects such as Landau damping Sulem et al 2016)) and intermittency corrections associated with coherent structures, such as current sheets (Boldyrev et al 2013), can also lead to steeper spectra. It should be stressed that both phenomenological arguments and numerical simulations predict a transition at d e , while observational spectra in the terrestrial magnetosheath only display a transition at ρ e (Huang et al 2014), associated with electron demagnetization.…”

Section: Resultsmentioning

confidence: 99%

Electron-scale reduced fluid models with gyroviscous effects

2017

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Reduced fluid models for collisionless plasmas including electron inertia and finite Larmor radius corrections are derived for scales ranging from the ion to the electron gyroradii. Based either on pressure balance or on the incompressibility of the electron fluid, they respectively capture kinetic Alfvén waves (KAWs) or whistler waves (WWs), and can provide suitable tools for reconnection and turbulence studies. Both isothermal regimes and Landau fluid closures permitting anisotropic pressure fluctuations are considered. For small values of the electron beta parameter β e , a perturbative computation of the gyroviscous force valid at scales comparable to the electron inertial length is performed at order O(β e ), which requires second-order contributions in a scale expansion. Comparisons with kinetic theory are performed in the linear regime. The spectrum of transverse magnetic fluctuations for strong and weak turbulence energy cascades is also phenomenologically predicted for both types of waves. In the case of moderate ion to electron temperature ratio, a new regime of KAW turbulence at scales smaller than the electron inertial length is obtained, where the magnetic energy spectrum decays like k −13/3 ⊥ , thus faster than the k −11/3 ⊥ spectrum of WW turbulence.

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Section: Resultsmentioning

confidence: 99%

Electron-scale reduced fluid models with gyroviscous effects

2017

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“…In these approaches, we observe a transition near the ion scales with a steepening in the magnetic field power and a simultaneous flattening in the electric field power fluctuations (Matthaeus et al 2008). Steeper spectra, as observed in the solar wind and in magnetospheres, have been often reproduced by the use of both 2D (Franci et al 2015b(Franci et al ,a, 2016b and 3D (see, e.g., Howes et al 2011;Franci et al 2018b) kinetics models, as well as in fluid models that include kinetic dissipative effects like the ion and electron Landau damping (Sulem et al 2016). It has been thus suggested than the steepening of the spectra is strictly correlated to deformations in the particle's velocity distribution function associated, for example, to wave-particle interactions such as instabilities and wave damping, to thermal anisotropies, and/or to non gyrotropic terms in the full pressure tensor (Del Sarto et al 2016;Del Sarto & Pegoraro 2018) that can drive dissipative effects (Yang et al 2017a).…”

Section: Introductionmentioning

confidence: 99%

Can Hall Magnetohydrodynamics Explain Plasma Turbulence at Sub-ion Scales?

Papini

Franci

Landi

et al. 2019

ApJ

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We investigate the properties of plasma turbulence by means of two-dimensional Hallmagnetohydrodynamic (HMHD) and hybrid particle-in-cell (HPIC) numerical simulations. We find that HMHD simulations exhibit spectral properties that are in most cases in agreement with the results of the HPIC simulations and with solar wind observations. The energy spectra of magnetic fluctuations exhibit a double power-law with spectral index −5/3 at MHD scales and −3 at kinetic scales, while for velocity fluctuations the spectral index is −3/2 at MHD scales. The break between the MHD and the kinetic scales occurs at the same scale in both simulations. In the MHD range the slopes of the total energy and residual energy spectra satisfy a fast Alfvén-dynamo balance. The development of a turbulent cascade is concurrently characterized by magnetic reconnection events taking place in thin current sheets that form between large eddies. A statistical analysis reveals that reconnection is qualitatively the same and fast in both the HMHD and HPIC models, characterized by inverse reconnection rates much smaller than the characteristic large-eddy nonlinear time. The agreement extends to other statistical properties, such us the kurtosis of the magnetic field. Moreover, the observation of a direct energy transfer from the large vortices to the small sub-ion scales triggered by magnetic reconnection, further supports the existence of a reconnection-mediated turbulent regime at kinetic scales. We conclude that the Hall-MHD fluid description captures to a large extent the transition of the turbulent cascade between the large MHD scales and the sub-ion scales.

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“…In order to investigate such complex dynamics, several analytical [11-16, 23, 24] and numerical [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] studies have been presented over the last few years. So far numerical studies have been performed mainly within a decaying turbulence framework, while a continuous forcing mechanism permits reaching a 'quasi-steady turbulent regime' over which the statistics of the performed analysis can be improved.…”

Section: Introductionmentioning

confidence: 99%

Reconnection and small-scale fields in 2D-3V hybrid-kinetic driven turbulence simulations

2017

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The understanding of the fundamental properties of turbulence in collisionless plasmas, such as the solar wind, is a frontier problem in plasma physics. In particular, the occurrence of magnetic reconnection in turbulent plasmas and its interplay with a fully-developed turbulent state is still a matter of great debate. Here we investigate the properties of small-scale electromagnetic fluctuations and the role of fast magnetic reconnection in the development of a quasi-steady turbulent state by means of 2D-3V high-resolution Vlasov-Maxwell simulations. At the largest scales turbulence is fed by external random forcing. We show that large-scale turbulent motions establish a -5 3 spectrum at < k d 1 i and, at the same time, feed the formation of current sheets where magnetic reconnection occurs. As a result coherent magnetic structures are generated which, together with the rise of the associated small-scale non-ideal electric field, mediate the transition between the inertial and the subproton-scale spectrum. A mechanism that boosts the magnetic reconnection process is identified, making the generation of coherent structures rapid enough to be competitive with wave mode interactions and leading to the formation of a fully-developed turbulent spectrum across the so-called ion break.

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Influence of the Nonlinearity Parameter on the Solar Wind Sub-Ion Magnetic Energy Spectrum: Flr–landau Fluid Simulations

Cited by 33 publications

References 45 publications

Electron-scale reduced fluid models with gyroviscous effects

Electron-scale reduced fluid models with gyroviscous effects

Can Hall Magnetohydrodynamics Explain Plasma Turbulence at Sub-ion Scales?

Reconnection and small-scale fields in 2D-3V hybrid-kinetic driven turbulence simulations

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