Dissipation and heating in solar wind turbulence: from the macro to the micro and back again

Kiyani, K. H.; Osman, K. T.; Chapman, Sandra C.

doi:10.1098/rsta.2014.0155

Cited by 187 publications

(167 citation statements)

References 47 publications

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“…While viscosity and resistivity are often invoked to model the dissipation in simulations of magnetohydrodynamic (MHD) turbulence, the collisionless nature of many space plasmas means a more complete description of the kinetic scales, where the fluid approximation breaks down, is needed to understand the small scales of plasma turbulence. Understanding how kinetic processes interact with a turbulent environment is currently an active area of research [14] and from a numerical standpoint is made difficult by the computational challenges associated with both obtaining the large scale separations inherent to turbulent flows, and accurately describing the kinetic scales of the plasma.…”

Section: Introductionmentioning

confidence: 99%

Small-scale behavior of Hall magnetohydrodynamic turbulence

Stawarz

Pouquet

2015

Phys. Rev. E

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Decaying Hall magnetohydrodynamic (HMHD) turbulence is studied using three-dimensional (3D) direct numerical simulations with grids up to 768 3 points and two different types of initial conditions. Results are compared to analogous magnetohydrodynamic (MHD) runs and both Laplacian and Laplacian squared dissipative operators are examined. At scales below the ion inertial length, the ratio of magnetic to kinetic energy as a function of wave number transitions to a magnetically dominated state. The transition in behavior is associated with the advection term in the momentum equation becoming subdominant to dissipation. Examination of autocorrelation functions reveals that, while current and vorticity structures are similarly sized in MHD, HMHD current structures are narrower and vorticity structures are wider. The electric field autocorrelation function is significantly narrower in HMHD than in MHD and is similar to the HMHD current autocorrelation function at small separations. HMHD current structures are found to be significantly more intense than in MHD and appear to have an enhanced association with strong alignment between the current and magnetic field, which may be important in collisionless plasmas where field-aligned currents can be unstable. When hyperdiffusivity is used, a longer region consistent with a k −7/3 scaling is present for right polarized fluctuations when compared to Laplacian dissipation runs.

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Section: Introductionmentioning

confidence: 99%

Small-scale behavior of Hall magnetohydrodynamic turbulence

Stawarz

Pouquet

2015

Phys. Rev. E

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“…It is not intended to be a complete review; for general review papers on solar wind observations see, e.g. Alexandrova et al (2013), Bruno & Carbone (2013) and the collection of Kiyani, Osman & Chapman (2015). It also primarily summarises work in which I have been involved, with other results and theoretical background described for context.…”

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confidence: 99%

Recent progress in astrophysical plasma turbulence from solar wind observations

2016

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This paper summarises some of the recent progress that has been made in understanding astrophysical plasma turbulence in the solar wind, from in situ spacecraft observations. At large scales, where the turbulence is predominantly Alfvénic, measurements of critical balance, residual energy and three-dimensional structure are discussed, along with comparison to recent models of strong Alfvénic turbulence. At these scales, a few per cent of the energy is also in compressive fluctuations, and their nature, anisotropy and relation to the Alfvénic component is described. In the small-scale kinetic range, below the ion gyroscale, the turbulence becomes predominantly kinetic Alfvén in nature, and measurements of the spectra, anisotropy and intermittency of this turbulence are discussed with respect to recent cascade models. One of the major remaining questions is how the turbulent energy is dissipated, and some recent work on this question, in addition to future space missions which will help to answer it, are briefly discussed.

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“…Although there is no universal agreement about the best way to quantitatively model the above chain of processes, we note that the idea of a turbulent cascade has been quite successful in predicting the heating rates and intermittency properties of the corona (e.g., van Ballegooijen 1986;Gómez et al 2000;Rappazzo et al 2008;van Ballegooijen et al 2011van Ballegooijen et al , 2014Dahlburg et al 2012;Kiyani et al 2015). In a plasma with a strong magnetic field, MHD turbulence is modulated by Alfvén waves, which propagate in both directions along the field and interact with one another nonlinearly.…”

Section: Coronal Heating From Wave Dissipationmentioning

confidence: 99%

Explaining Inverted-Temperature Loops in the Quiet Solar Corona With Magnetohydrodynamic Wave-Mode Conversion

Schiff

Cranmer

2016

ApJ

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Coronal loops trace out bipolar, arch-like magnetic fields above the Sun's surface. Recent measurements that combine rotational tomography, extreme ultraviolet imaging, and potential-field extrapolation have shown the existence of large loops with inverted temperature profiles; i.e., loops for which the apex temperature is a local minimum, not a maximum. These "down loops" appear to exist primarily in equatorial quiet regions near solar minimum. We simulate both these and the more prevalent large-scale "up loops" by modeling coronal heating as a time-steady superposition of: (1) dissipation of incompressible Alfvén-wave turbulence, and (2) dissipation of compressive waves formed by mode conversion from the initial population of Alfvén waves. We found that when a large percentage (> 99%) of the Alfvén waves undergo this conversion, heating is greatly concentrated at the footpoints and stable "down loops" are created. In some cases we found loops with three maxima that are also gravitationally stable. Models that agree with the tomographic temperature data exhibit higher gas pressures for "down loops" than for "up loops," which is consistent with observations. These models also show a narrow range of Alfvén wave amplitudes: 3 to 6 km s −1 at the coronal base. This is low in comparison to typical observed amplitudes of 20 to 30 km s −1 in bright X-ray loops. However, the large-scale loops we model are believed to comprise a weaker diffuse background that fills much of the volume of the corona. By constraining the physics of loops that underlie quiescent streamers, we hope to better understand the formation of the slow solar wind.

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Dissipation and heating in solar wind turbulence: from the macro to the micro and back again

Cited by 187 publications

References 47 publications

Small-scale behavior of Hall magnetohydrodynamic turbulence

Small-scale behavior of Hall magnetohydrodynamic turbulence

Recent progress in astrophysical plasma turbulence from solar wind observations

Explaining Inverted-Temperature Loops in the Quiet Solar Corona With Magnetohydrodynamic Wave-Mode Conversion

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