TY - JOUR
T1 - Dual Phase-space Cascades in 3D Hybrid-Vlasov-Maxwell Turbulence
AU - Cerri, S. S.
AU - Kunz, Matthew Walter
AU - Califano, F.
N1 - Funding Information:
The authors thank Lev Arzamasskiy, Yuri Cavecchi, and especially Alex Schekochihin for valuable conversations, as well as the anonymous referee for a prompt and constructive report. S.S.C.and F.C.acknowledge Carlo Cavazzoni (CINECA, Italy) for essential contributions to the parallelization and optimization of the HVM code. The simulation was performed at CINECA (Italy) under the ISCRA initiative (grant HP10BEANCY). S.S.C.and M.W.K.were supported by the National Aeronautics and Space Administration under grant No.NNX16AK09G issued through the Heliophysics Supporting Research Program.
Publisher Copyright:
© 2018. The American Astronomical Society. All rights reserved.
PY - 2018/3/20
Y1 - 2018/3/20
N2 - To explain energy dissipation via turbulence in collisionless, magnetized plasmas, the existence of a dual real- and velocity-space cascade of ion-entropy fluctuations below the ion gyroradius has been proposed. Such a dual cascade, predicted by the gyrokinetic theory, has previously been observed in gyrokinetic simulations of two-dimensional, electrostatic turbulence. For the first time, we show evidence for a dual phase-space cascade of ion-entropy fluctuations in a three-dimensional simulation of hybrid-kinetic, electromagnetic turbulence. Some of the scalings observed in the energy spectra are consistent with a generalized theory for the cascade that accounts for the spectral anisotropy of critically balanced, intermittent, sub-ion-Larmor-scale fluctuations. The observed velocity-space cascade is also anisotropic with respect to the magnetic-field direction, with linear phase mixing along magnetic-field lines proceeding mainly at spatial scales above the ion gyroradius and nonlinear phase mixing across magnetic-field lines proceeding at perpendicular scales below the ion gyroradius. Such phase-space anisotropy could be sought in heliospheric and magnetospheric data of solar-wind turbulence and has far-reaching implications for the dissipation of turbulence in weakly collisional astrophysical plasmas.
AB - To explain energy dissipation via turbulence in collisionless, magnetized plasmas, the existence of a dual real- and velocity-space cascade of ion-entropy fluctuations below the ion gyroradius has been proposed. Such a dual cascade, predicted by the gyrokinetic theory, has previously been observed in gyrokinetic simulations of two-dimensional, electrostatic turbulence. For the first time, we show evidence for a dual phase-space cascade of ion-entropy fluctuations in a three-dimensional simulation of hybrid-kinetic, electromagnetic turbulence. Some of the scalings observed in the energy spectra are consistent with a generalized theory for the cascade that accounts for the spectral anisotropy of critically balanced, intermittent, sub-ion-Larmor-scale fluctuations. The observed velocity-space cascade is also anisotropic with respect to the magnetic-field direction, with linear phase mixing along magnetic-field lines proceeding mainly at spatial scales above the ion gyroradius and nonlinear phase mixing across magnetic-field lines proceeding at perpendicular scales below the ion gyroradius. Such phase-space anisotropy could be sought in heliospheric and magnetospheric data of solar-wind turbulence and has far-reaching implications for the dissipation of turbulence in weakly collisional astrophysical plasmas.
KW - methods: numerical
KW - plasmas
KW - solar wind
KW - turbulence
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U2 - 10.3847/2041-8213/aab557
DO - 10.3847/2041-8213/aab557
M3 - Article
AN - SCOPUS:85044788671
SN - 2041-8205
VL - 856
JO - Astrophysical Journal Letters
JF - Astrophysical Journal Letters
IS - 1
M1 - L13
ER -