Alfvén wave collisions, the fundamental building block of plasma turbulence. II. Numerical solution

Nielson, Kevin; Howes, G. G.; Dorland, W.

doi:10.1063/1.4812807

Cited by 40 publications

(67 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Various explanations for why r A <1 have been advanced, including local in k ‐space dynamo action [ Pouquet et al , ; Grappin et al , ], small‐scale reconnection, with current sheets more intense than the nearby vorticity coherent structures [ Matthaeus and Lamkin , ], and a perturbation theory approach that indicates two counterpropagating Alfvén waves drive a k z =0 purely magnetic structure [ Howes and Nielson , ; Nielson et al , ]. For the case of solar wind fluctuations, Yokoi [] has shown that an approximately distance‐independent value of r A ≈1/2 emerges as a consequence of balance between the dominant terms in a (time steady) transport equation for the energy difference, E v − E b (equivalent to r A ).…”

Section: Resultsmentioning

confidence: 99%

Variance anisotropy in compressible 3‐D MHD

et al. 2016

View full text Add to dashboard Cite

We employ spectral method numerical simulations to examine the dynamical development of anisotropy of the variance, or polarization, of the magnetic and velocity field in compressible magnetohydrodynamic (MHD) turbulence. Both variance anisotropy and spectral anisotropy emerge under influence of a large‐scale mean magnetic field B0; these are distinct effects, although sometimes related. Here we examine the appearance of variance parallel to B0, when starting from a highly anisotropic state. The discussion is based on a turbulence theoretic approach rather than a wave perspective. We find that parallel variance emerges over several characteristic nonlinear times, often attaining a quasi‐steady level that depends on plasma beta. Consistency with solar wind observations seems to occur when the initial state is dominated by quasi‐two‐dimensional fluctuations.

show abstract

Section: Resultsmentioning

confidence: 99%

Variance anisotropy in compressible 3‐D MHD

et al. 2016

View full text Add to dashboard Cite

show abstract

“…In the Large Plasma Device (LAPD ) at UCLA, 9 experiments have been conducted to understand the nonlinear evolution of Alfvén wave collisions 115 -the nonlinear interactions among counterpropagating Alfvén waves, proposed as the fundamental mechanism mediating turbulent energy transfer to small scales in early studies of MHD turbulence. 116,117 Asymptotic analytical solutions for the evolution of Alfvén wave collisions in the weakly nonlinear limit 115 have been confirmed numerically with gyrokinetic numerical simulations in the MHD regime 118 and verified experimentally in the laboratory, 119-123 establishing Alfvén wave collisions as the fundamental building block of astrophysical plasma turbulence. The success of this experimental investigation of Alfvén wave collisions has laid the foundation for subsequent advances in our theoretical understanding of how current sheets arise self-consistently in plasma turbulence, 70,124 the role played by resonant wave-particle interactions in the dissipation of these current sheets, 72 and how collisions between localized Alfvén wavepackets in the strongly nonlinear limit mediate the turbulent cascade of energy to small scales.…”

Section: A Plasma Turbulencementioning

confidence: 85%

Laboratory space physics: Investigating the physics of space plasmas in the laboratory

Howes

2018

Physics of Plasmas

View full text Add to dashboard Cite

Laboratory experiments provide a valuable complement to explore the fundamental physics of space plasmas without the limitations inherent to spacecraft measurements. Specifically, experiments overcome the restriction that spacecraft measurements are made at only one (or a few) points in space, enable greater control of the plasma conditions and applied perturbations, can be reproducible, and are orders of magnitude less expensive than launching spacecraft. Here I highlight key open questions about the physics of space plasmas and identify the aspects of these problems that can potentially be tackled in laboratory experiments. Several past successes in laboratory space physics provide concrete examples of how complementary experiments can contribute to our understanding of physical processes at play in the solar corona, solar wind, planetary magnetospheres, and outer boundary of the heliosphere. I present developments on the horizon of laboratory space physics, identifying velocity space as a key new frontier, highlighting new and enhanced experimental facilities, and showcasing anticipated developments to produce improved diagnostics and innovative analysis methods. A strategy for future laboratory space physics investigations will be outlined, with explicit connections to specific fundamental plasma phenomena of interest.

show abstract

“…The amplitude of the initial wavepackets is parameterized by the nonlinearity parameter (Goldreich & Sridhar 1995), defined by taking the ratio of the magnitudes of the linear to the nonlinear terms in the incompressible MHD equations Nielson et al 2013). In terms of Elsasser variables, defined by z ± = u±δB/ 4π(n 0i m i + n 0e m e ), the nonlinearity parameter is defined by χ ± ≡ |z ∓ · ∇z ± |/|v A · ∇z ± |, where χ ± characterizes the strength of the nonlinear distortion of the z ± Alfvén wave by the counterpropagating z ∓ Alfvén wave.…”

Section: Simulationmentioning

confidence: 99%

The Alfvénic nature of energy transfer mediation in localized, strongly nonlinear Alfvén wavepacket collisions

Verniero

Howes

2018

J. Plasma Phys.

View full text Add to dashboard Cite

In space and astrophysical plasmas, violent events or instabilities inject energy into turbulent motions at large scales. Nonlinear interactions among the turbulent fluctuations drive a cascade of energy to small perpendicular scales at which the energy is ultimately converted into plasma heat. Previous work with the incompressible magnetohydrodynamic (MHD) equations has shown that this turbulent energy cascade is driven by the nonlinear interaction between counterpropagating Alfvén waves -also known as Alfvén wave collisions. Direct numerical simulations of weakly collisional plasma turbulence enables deeper insight into the nature of the nonlinear interactions underlying the turbulent cascade of energy. In this paper, we directly compare four cases: both periodic and localized Alfvén wave collisions in the weakly and strongly nonlinear limits. Our results reveal that in the more realistic case of localized Alfvén wave collisions (rather than the periodic case), all nonlinearly generated fluctuations are Alfvén waves, which mediates nonlinear energy transfer to smaller perpendicular scales.

show abstract

Alfvén wave collisions, the fundamental building block of plasma turbulence. II. Numerical solution

Cited by 40 publications

References 19 publications

Variance anisotropy in compressible 3‐D MHD

Variance anisotropy in compressible 3‐D MHD

Laboratory space physics: Investigating the physics of space plasmas in the laboratory

The Alfvénic nature of energy transfer mediation in localized, strongly nonlinear Alfvén wavepacket collisions

Contact Info

Product

Resources

About