2,410 research outputs found
Multiscale nature of the dissipation range in gyrokinetic simulations of Alfv\'enic turbulence
Nonlinear energy transfer and dissipation in Alfv\'en wave turbulence are
analyzed in the first gyrokinetic simulation spanning all scales from the tail
of the MHD range to the electron gyroradius scale. For typical solar wind
parameters at 1 AU, about 30% of the nonlinear energy transfer close to the
electron gyroradius scale is mediated by modes in the tail of the MHD cascade.
Collisional dissipation occurs across the entire kinetic range
. Both mechanisms thus act on multiple coupled scales,
which have to be retained for a comprehensive picture of the dissipation range
in Alfv\'enic turbulence.Comment: Made several improvements to figures and text suggested by referee
Kinetic Scale Density Fluctuations in the Solar Wind
We motivate the importance of studying kinetic scale turbulence for
understanding the macroscopic properties of the heliosphere, such as the
heating of the solar wind. We then discuss the technique by which kinetic scale
density fluctuations can be measured using the spacecraft potential, including
a calculation of the timescale for the spacecraft potential to react to the
density changes. Finally, we compare the shape of the density spectrum at ion
scales to theoretical predictions based on a cascade model for kinetic
turbulence. We conclude that the shape of the spectrum, including the ion scale
flattening, can be captured by the sum of passive density fluctuations at large
scales and kinetic Alfven wave turbulence at small scales
He Wandered Down The Beaten Path : Song and Chorus
https://digitalcommons.library.umaine.edu/mmb-vp/1560/thumbnail.jp
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
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