High-resolution hybrid simulations of kinetic plasma turbulence at proton scales
File(s)Franci_al_ApJ2015.pdf (2.28 MB)
Published version
Author(s)
Franci, L
Landi, S
Matteini, L
Verdini, A
Hellinger, P
Type
Journal Article
Abstract
We investigate properties of plasma turbulence from magnetohydrodynamic (MHD) to sub-ion scales by means of
two-dimensional, high-resolution hybrid particle-in-cell simulations. We impose an initial ambient magnetic
field perpendicular to the simulation box, and we add a spectrum of large-scale magnetic and kinetic
fluctuations with energy equipartition and vanishing correlation. Once the turbulence is fully developed, we
observe an MHD inertial range, where the spectra of the perpendicular magnetic field and the perpendicular proton
bulk velocity fluctuations exhibit power-law scaling with spectral indices of -5 3 and -3 2, respectively. This
behavior is extended over a full decade in wavevectors and is very stable in time. A transition is observed around
proton scales. At sub-ion scales, both spectra steepen, with the former still following a power law with a spectral
index of ~-3. A-2.8 slope is observed in the density and parallel magnetic fluctuations, highlighting the presence
of compressive effects at kinetic scales. The spectrum of the perpendicular electric fluctuations follows that of the
proton bulk velocity at MHD scales, and flattens at small scales. All these features, which we carefully tested
against variations of many parameters, are in good agreement with solar wind observations. The turbulent cascade
leads to on overall proton energization with similar heating rates in the parallel and perpendicular directions. While
the parallel proton heating is found to be independent on the resistivity, the number of particles per cell, and the
resolution employed, the perpendicular proton temperature strongly depends on these parameters.
two-dimensional, high-resolution hybrid particle-in-cell simulations. We impose an initial ambient magnetic
field perpendicular to the simulation box, and we add a spectrum of large-scale magnetic and kinetic
fluctuations with energy equipartition and vanishing correlation. Once the turbulence is fully developed, we
observe an MHD inertial range, where the spectra of the perpendicular magnetic field and the perpendicular proton
bulk velocity fluctuations exhibit power-law scaling with spectral indices of -5 3 and -3 2, respectively. This
behavior is extended over a full decade in wavevectors and is very stable in time. A transition is observed around
proton scales. At sub-ion scales, both spectra steepen, with the former still following a power law with a spectral
index of ~-3. A-2.8 slope is observed in the density and parallel magnetic fluctuations, highlighting the presence
of compressive effects at kinetic scales. The spectrum of the perpendicular electric fluctuations follows that of the
proton bulk velocity at MHD scales, and flattens at small scales. All these features, which we carefully tested
against variations of many parameters, are in good agreement with solar wind observations. The turbulent cascade
leads to on overall proton energization with similar heating rates in the parallel and perpendicular directions. While
the parallel proton heating is found to be independent on the resistivity, the number of particles per cell, and the
resolution employed, the perpendicular proton temperature strongly depends on these parameters.
Date Issued
2015-10-06
Date Acceptance
2015-09-01
Citation
Astrophysical Journal, 2015, 812 (1)
ISSN
1538-4357
Publisher
American Astronomical Society
Journal / Book Title
Astrophysical Journal
Volume
812
Issue
1
Copyright Statement
© 2015. The American Astronomical Society. All rights reserved
Sponsor
Science and Technology Facilities Council (STFC)
Science and Technology Facilities Council [2006-2012]
Grant Number
ST/K001051/1
ST/K001051/1
Subjects
Science & Technology
Physical Sciences
Astronomy & Astrophysics
plasmas
solar wind
turbulence
SOLAR-WIND TURBULENCE
ELECTRON MAGNETOHYDRODYNAMIC TURBULENCE
TEMPERATURE ANISOTROPY
DISSIPATION RANGE
ENERGY CASCADE
MAGNETIC FLUCTUATIONS
ALFVENIC TURBULENCE
CURRENT SHEETS
1 AU
ION
Publication Status
Published
Article Number
ARTN 21