Energy Cascade Rate in Compressible Fast and Slow Solar Wind Turbulence

Estimation of the energy cascade rate in the inertial range of solar wind turbulence has been done so far mostly within incompressible magnetohydrodynamics (MHD) theory. Here, we go beyond that approximation to include plasma compressibility using a reduced form of a recently derived exact law for c...

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Bibliographic Details
Published in:The Astrophysical journal 2017-03, Vol.838 (1), p.9
Main Authors: Hadid, L. Z., Sahraoui, F., Galtier, S.
Format: Article
Language:English
Subjects:
ANISOTROPY
APPROXIMATIONS
Astrophysics
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
COMPARATIVE EVALUATIONS
COMPRESSIBILITY
Computational fluid dynamics
Energy
FLUCTUATIONS
FORECASTING
MACH NUMBER
Magnetohydrodynamic turbulence
MAGNETOHYDRODYNAMICS
magnetohydrodynamics (MHD)
Physics
PLASMA
Plasma Physics
plasmas
Power law
SOLAR WIND
Solar wind turbulence
SPACE VEHICLES
Spacecraft
TURBULENCE
WASTE HEAT UTILIZATION
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Summary:Estimation of the energy cascade rate in the inertial range of solar wind turbulence has been done so far mostly within incompressible magnetohydrodynamics (MHD) theory. Here, we go beyond that approximation to include plasma compressibility using a reduced form of a recently derived exact law for compressible, isothermal MHD turbulence. Using in situ data from the THEMIS/ARTEMIS spacecraft in the fast and slow solar wind, we investigate in detail the role of the compressible fluctuations in modifying the energy cascade rate with respect to the prediction of the incompressible MHD model. In particular, we found that the energy cascade rate (1) is amplified particularly in the slow solar wind; (2) exhibits weaker fluctuations in spatial scales, which leads to a broader inertial range than the previous reported ones; (3) has a power-law scaling with the turbulent Mach number; (4) has a lower level of spatial anisotropy. Other features of solar wind turbulence are discussed along with their comparison with previous studies that used incompressible or heuristic (nonexact) compressible MHD models.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/aa603f