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von Kármán-Howarth equation for three-dimensional two-fluid plasmas
N Andrés1,2, P D Mininni2,3, P Dmitruk2,3
1Instituto de Astronomía y Física del Espacio, CONICET-UBA, Ciudad Universitaria, 1428 Buenos Aires, Argentina.
Physical Review. E
|July 15, 2016
Summary
Researchers derived the plasma four-fifths law for turbulent dynamics. This exact law predicts scaling for third-order correlations, aiding solar wind measurements.
Area of Science:
- Plasma physics
- Turbulence theory
- Fluid dynamics
Background:
- The von Kármán-Howarth equation is fundamental in describing turbulence.
- Understanding turbulent dynamics in plasmas is crucial for astrophysical phenomena.
- Previous studies focused on hydrodynamic turbulence, with less on plasma specifics.
Purpose of the Study:
- To derive the von Kármán-Howarth equation for a three-dimensional incompressible two-fluid plasma.
- To obtain the plasma equivalent of the hydrodynamic "four-fifths" law.
- To provide a tool for analyzing in situ solar wind data.
Main Methods:
- Derivation of the von Kármán-Howarth equation for a two-fluid plasma.
- Analysis in the long-time limit and for very large Reynolds numbers.
- Expression of the four-fifths law in terms of third-order structure functions.
Main Results:
- An exact plasma equivalent of the hydrodynamic "four-fifths" law was obtained.
- This law predicts the scaling of third-order two-point correlation functions.
- A simplified expression for the four-fifths law was derived for empirical comparison.
Conclusions:
- The derived "four-fifths" law imposes a strong constraint on plasma turbulent dynamics.
- The findings offer a new method for analyzing solar wind turbulence.
- This work bridges theoretical plasma turbulence with observational data.
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