Dependence of Kinetic Plasma Turbulence on Plasma β

Parashar, T. N.; Matthaeus, W. H.; Shay, M. A.

doi:10.3847/2041-8213/aadb8b

Cited by 53 publications

(27 citation statements)

References 53 publications

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“…For a given quantity Y (e.g., a component of the magnetic field, bulk velocity field) and a separation length l, the increment, ∆Y , the difference between two points separated by l, has generally a non-Gaussian distribution. This non-Gaussianity is well characterized by the excess kurtosis (flatness) that is close to zero on large scales (compatible with a Gaussian statistics) but it increases as l de-creases in the inertial ranges; behavior of the kurtosis in the sub-ion range is not well known, some results indicate that it further increases (e.g., Alexandrova et al 2008;Franci et al 2015) but some observations and numerical simulations indicate that the kurtosis saturates and even decreases in the sub-ion range (e.g., Wu et al 2013;Parashar et al 2018). The non-Gaussian statistics with extreme values is often associated with localized/coherent structures that appear to be important for the particle energization (Matthaeus et al 2015); these energization/dissipation processes could be responsible for the decrease of the kurtosis.…”

Section: Introductionmentioning

confidence: 93%

Turbulence versus Fire-hose Instabilities: 3D Hybrid Expanding Box Simulations

Hellinger

Matteini

Landi

et al. 2019

ApJ

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The relationship between a decaying plasma turbulence and proton fire hose instabilities in a slowly expanding plasma is investigated using three-dimensional (3-D) hybrid expanding box simulations. We impose an initial ambient magnetic field along the radial direction, and we start with an isotropic spectrum of large-scale, linearly-polarized, random-phase Alfvénic fluctuations with zero cross-helicity. A turbulent cascade rapidly develops and leads to a weak proton heating that is not sufficient to overcome the expansion-driven perpendicular cooling. The plasma system eventually drives the parallel and oblique fire hose instabilities that generate quasi-monochromatic wave packets that reduce the proton temperature anisotropy. The fire hose wave activity has a low amplitude with wave vectors quasi-parallel/oblique with respect to the ambient magnetic field outside of the region dominated by the turbulent cascade and is discernible in one-dimensional power spectra taken only in the direction quasi-parallel/oblique with respect to the ambient magnetic field; at quasi-perpendicular angles the wave activity is hidden by the turbulent background. These waves are partly reabsorbed by protons and partly couple to and participate in the turbulent cascade. Their presence reduces kurtosis, a measure of intermittency, and the Shannon entropy but increases the Jensen-Shannon complexity of magnetic fluctuations; these changes are weak and anisotropic with respect to the ambient magnetic field and it's not clear if they can be used to indirectly discern the presence of instability-driven waves. arXiv:1908.07760v1 [physics.space-ph]

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Section: Introductionmentioning

confidence: 93%

Turbulence versus Fire-hose Instabilities: 3D Hybrid Expanding Box Simulations

Hellinger

Matteini

Landi

et al. 2019

ApJ

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“…Grošelj et al. 2017; Guo, Sironi & Narayan 2017; Parashar, Matthaeus & Shay 2018; Arzamasskiy et al. 2019; Cerri, Grošelj & Franci 2019; Kawazura et al.…”

Section: Theory Of the Kaufmann And Paterson Non-maxwellianitymentioning

confidence: 99%

Kinetic entropy-based measures of distribution function non-Maxwellianity: theory and simulations

et al. 2020

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We investigate kinetic entropy-based measures of the non-Maxwellianity of distribution functions in plasmas, i.e. entropy-based measures of the departure of a local distribution function from an associated Maxwellian distribution function with the same density, bulk flow and temperature as the local distribution. First, we consider a form previously employed by Kaufmann & Paterson (J. Geophys. Res., vol. 114, 2009, A00D04), assessing its properties and deriving equivalent forms. To provide a quantitative understanding of it, we derive analytical expressions for three common non-Maxwellian plasma distribution functions. We show that there are undesirable features of this non-Maxwellianity measure including that it can diverge in various physical limits and elucidate the reason for the divergence. We then introduce a new kinetic entropy-based non-Maxwellianity measure based on the velocity-space kinetic entropy density, which has a meaningful physical interpretation and does not diverge. We use collisionless particle-in-cell simulations of two-dimensional anti-parallel magnetic reconnection to assess the kinetic entropy-based non-Maxwellianity measures. We show that regions of non-zero non-Maxwellianity are linked to kinetic processes occurring during magnetic reconnection. We also show the simulated non-Maxwellianity agrees reasonably well with predictions for distributions resembling those calculated analytically. These results can be important for applications, as non-Maxwellianity can be used to identify regions of kinetic-scale physics or increased dissipation in plasmas.

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“…Q T (r) is the turbulent heating, which is apportioned between protons and electrons according to the fraction f p that must be determined by kinetic physics considerations. Recent kinetic plasma simulation and theory provide predictions for f p , which increases with turbulence amplitude (Wu et al 2013;Matthaeus et al 2016a;Gary et al 2016) and also depends on the plasma β (Parashar et al 2018;Kawazura et al 2019). Note that the turbulent heating depends on position r.…”

Section: Solar Wind Model and Turbulence Transport Modelmentioning

confidence: 99%

Contextual Predictions forParker Solar Probe. II. Turbulence Properties and Taylor Hypothesis

Chhiber

Usmanov

Matthaeus

et al. 2019

ApJS

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The Parker Solar Probe (PSP ) primary mission extends seven years and consists of 24 orbits of the Sun with descending perihelia culminating in a closest approach of ∼ 9.8 R . In the course of these orbits PSP will pass through widely varying conditions, including anticipated large variations of turbulence properties such as energy density, correlation scales and cross helicities. Here we employ global magnetohydrodynamics simulations with self-consistent turbulence transport and heating to preview likely conditions that will be encountered by PSP, by assuming suitable boundary conditions at the coronal base. The code evolves large-scale parameters -such as velocity, magnetic field, and temperature -as well as turbulent energy density, cross helicity, and correlation scale. These computed quantities provide the basis for evaluating additional useful parameters that are derivable from the primary model outputs. Here we illustrate one such possibility in which computed turbulence and large-scale parameters are used to evaluate the accuracy of the Taylor "frozen-in" hypothesis along the PSP trajectory. Apart from the immediate purpose of anticipating turbulence conditions that PSP will encounter, as experience is gained in comparisons of observations with simulated data, this approach will be increasingly useful for planning and interpretation of subsequent observations.

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Dependence of Kinetic Plasma Turbulence on Plasma β

Cited by 53 publications

References 53 publications

Turbulence versus Fire-hose Instabilities: 3D Hybrid Expanding Box Simulations

Turbulence versus Fire-hose Instabilities: 3D Hybrid Expanding Box Simulations

Kinetic entropy-based measures of distribution function non-Maxwellianity: theory and simulations

Contextual Predictions forParker Solar Probe. II. Turbulence Properties and Taylor Hypothesis

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