2,863 research outputs found
Evidence of Critical Balance in Kinetic Alfven Wave Turbulence Simulations
A numerical simulation of kinetic plasma turbulence is performed to assess
the applicability of critical balance to kinetic, dissipation scale turbulence.
The analysis is performed in the frequency domain to obviate complications
inherent in performing a local analysis of turbulence. A theoretical model of
dissipation scale critical balance is constructed and compared to simulation
results, and excellent agreement is found. This result constitutes the first
evidence of critical balance in a kinetic turbulence simulation and provides
evidence of an anisotropic turbulence cascade extending into the dissipation
range. We also perform an Eulerian frequency analysis of the simulation data
and compare it to the results of a previous study of magnetohydrodynamic
turbulence simulations.Comment: 10 pages, 9 figures, accepted for publication in Physics of Plasma
Gyrokinetic Simulations of Solar Wind Turbulence from Ion to Electron Scales
The first three-dimensional, nonlinear gyrokinetic simulation of plasma
turbulence resolving scales from the ion to electron gyroradius with a
realistic mass ratio is presented, where all damping is provided by resolved
physical mechanisms. The resulting energy spectra are quantitatively consistent
with a magnetic power spectrum scaling of as observed in \emph{in
situ} spacecraft measurements of the "dissipation range" of solar wind
turbulence. Despite the strongly nonlinear nature of the turbulence, the linear
kinetic \Alfven wave mode quantitatively describes the polarization of the
turbulent fluctuations. The collisional ion heating is measured at
sub-ion-Larmor radius scales, which provides the first evidence of the ion
entropy cascade in an electromagnetic turbulence simulation.Comment: 4 pages, 2 figures, submitted to Phys. Rev. Let
Environmental sustainability: A case of policy implementation failure?
© 2017 by the author. For a generation, governments around the world have been committed to sustainable development as a policy goal. This has been supported by an array of new policies ranging from international agreements, to national strategies, environmental laws at many levels of government, regional programs, and local plans. Despite these efforts, decades of scientific monitoring indicate that the world is no closer to environmental sustainability and in many respects the situation is getting worse. This paper argues that a significant contributing factor to this situation is policy implementation failure. A systematic review of the literature reveals that the failure to achieve the intended outcomes of environmental policies is due to economic, political and communication factors. Conflict between the objectives of environmental policies and those focused on economic development, a lack of incentives to implement environmental policies, and a failure to communicate objectives to key stakeholders are all key factors that contribute to the inability to attain environmental sustainability
The order parameter of the chiral Potts model
An outstanding problem in statistical mechanics is the order parameter of the
chiral Potts model. An elegant conjecture for this was made in 1983. It has
since been successfully tested against series expansions, but as far as the
author is aware there is as yet no proof of the conjecture. Here we show that
if one makes a certain analyticity assumption similar to that used to derive
the free energy, then one can indeed verify the conjecture. The method is based
on the ``broken rapidity line'' approach pioneered by Jimbo, Miwa and
Nakayashiki.Comment: 29 pages, 7 figures. Citations made more explicit and some typos
correcte
Kinetic Turbulence
The weak collisionality typical of turbulence in many diffuse astrophysical
plasmas invalidates an MHD description of the turbulent dynamics, motivating
the development of a more comprehensive theory of kinetic turbulence. In
particular, a kinetic approach is essential for the investigation of the
physical mechanisms responsible for the dissipation of astrophysical turbulence
and the resulting heating of the plasma. This chapter reviews the limitations
of MHD turbulence theory and explains how kinetic considerations may be
incorporated to obtain a kinetic theory for astrophysical plasma turbulence.
Key questions about the nature of kinetic turbulence that drive current
research efforts are identified. A comprehensive model of the kinetic turbulent
cascade is presented, with a detailed discussion of each component of the model
and a review of supporting and conflicting theoretical, numerical, and
observational evidence.Comment: 31 pages, 3 figures, 99 references, Chapter 6 in A. Lazarian et al.
(eds.), Magnetic Fields in Diffuse Media, Astrophysics and Space Science
Library 407, Springer-Verlag Berlin Heidelberg (2015
- …