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

Abstract

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.

Authors:

Verniero, J.  L.; Howes, G.  G.

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Publication Date:

2018-01-30

Research Org.:

Univ. of Iowa, Iowa City, IA (United States)

Sponsoring Org.:

USDOE Office of Science (SC)

OSTI Identifier:

1538934

DOE Contract Number:  

SC0014599

Resource Type:

Journal Article

Journal Name:

Journal of Plasma Physics

Additional Journal Information:

Journal Volume: 84; Journal Issue: 1; Journal ID: ISSN 0022-3778

Publisher:

Cambridge University Press

Country of Publication:

United States

Language:

English

Subject:

Physics