We study the properties of plasma turbulence at subproton scales using kinetic electromagnetic three-dimensional simulations with nonidentical initial conditions. Particle-in-cell modeling of the Taylor-Green vortex has been performed, starting from three different magnetic field configurations. All simulations expose very similar energy evolution in which the large-scale ion flows and magnetic structures deteriorate and transfer their energy into particle heating. Heating is more intense for electrons, decreasing the initial temperature ratio and leading to temperature equipartition between the two species. A full turbulent cascade, with a well-defined power-law shape at subproton scales, is established within a characteristic turnover time. Spectral indices for magnetic field fluctuations in two simulations are close to α B ≈ 2.9, and are steeper in the remaining case with α B ≈ 3.05. Energy is dissipated by a complex mixture of plasma instabilities and magnetic reconnection and is milder in the latter simulation. The number of magnetic nulls, and the dissipation pattern observed in this case, differ from two others. Spectral indices for the kinetic energy deviate from magnetic spectra by ≈1 in the first simulation, and by ≈0.75 in two other runs. The difference between magnetic and electric slopes confirm the previously observed value of α B - α E ≈ 2.
Properties of Decaying Plasma Turbulence at Subproton Scales
S. Servidio
;PUCCI, FRANCESCO;L. Primavera;
2018-01-01
Abstract
We study the properties of plasma turbulence at subproton scales using kinetic electromagnetic three-dimensional simulations with nonidentical initial conditions. Particle-in-cell modeling of the Taylor-Green vortex has been performed, starting from three different magnetic field configurations. All simulations expose very similar energy evolution in which the large-scale ion flows and magnetic structures deteriorate and transfer their energy into particle heating. Heating is more intense for electrons, decreasing the initial temperature ratio and leading to temperature equipartition between the two species. A full turbulent cascade, with a well-defined power-law shape at subproton scales, is established within a characteristic turnover time. Spectral indices for magnetic field fluctuations in two simulations are close to α B ≈ 2.9, and are steeper in the remaining case with α B ≈ 3.05. Energy is dissipated by a complex mixture of plasma instabilities and magnetic reconnection and is milder in the latter simulation. The number of magnetic nulls, and the dissipation pattern observed in this case, differ from two others. Spectral indices for the kinetic energy deviate from magnetic spectra by ≈1 in the first simulation, and by ≈0.75 in two other runs. The difference between magnetic and electric slopes confirm the previously observed value of α B - α E ≈ 2.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
