Abstract
The properties of supersonic, compressible plasma turbulence determine the behavior of many terrestrial and astrophysical systems. In the interstellar medium and molecular clouds, compressible turbulence plays a vital role in star formation and the evolution of our galaxy. Observations of the density and velocity power spectra in the Orion B and Perseus molecular clouds show large deviations from those predicted for incompressible turbulence. Hydrodynamic simulations attribute this to the high Mach number in the interstellar medium (ISM), although the exact details of this dependence are not well understood. Here we investigate experimentally the statistical behavior of boundary-free supersonic turbulence created by the collision of two laser-driven high-velocity turbulent plasma jets. The Mach number dependence of the slopes of the density and velocity power spectra agree with astrophysical observations, and supports the notion that the turbulence transitions from being Kolmogorov-like at low Mach number to being more Burgers-like at higher Mach numbers.
Highlights
The properties of supersonic, compressible plasma turbulence determine the behavior of many terrestrial and astrophysical systems
Attempts to characterize the statistical behavior of supersonic turbulence have far comprised theoretical predictions[11,12,13,14], astrophysical observations[15,16,17], and hydrodynamic simulations[8,18,19,20]
We provide a detailed characterization of the bulk properties of compressible turbulence in a super-Alfvénic plasma based on laboratory experiments performed with high-power lasers
Summary
The properties of supersonic, compressible plasma turbulence determine the behavior of many terrestrial and astrophysical systems. Observations of the density and velocity power spectra in the Orion B and Perseus molecular clouds show large deviations from those predicted for incompressible turbulence. Hydrodynamic simulations attribute this to the high Mach number in the interstellar medium (ISM), the exact details of this dependence are not well understood. We investigate experimentally the statistical behavior of boundary-free supersonic turbulence created by the collision of two laser-driven high-velocity turbulent plasma jets. We provide a detailed characterization of the bulk properties of compressible turbulence in a super-Alfvénic plasma based on laboratory experiments performed with high-power lasers. The outerscale motions are made more chaotic by letting the jets pass through two offset grids before the collision, driving turbulence at a scale-length of roughly twice the grid spacing, or 2 mm
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