Temporal and spatial turbulent spectra of MHD plasma and an observation of variance anisotropy

Journal Article · Fri Aug 01 04:00:00 EDT 2014 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/790/2/126· OSTI ID:22365488

Schaffner, D. A.; Brown, M. R. ^[1]; Lukin, V. S. ^[2]

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1. Swarthmore College, Swarthmore, PA (United States)
2. Space Science Division, Naval Research Laboratory, Washington, DC (United States)

The nature of magnetohydrodynamic (MHD) turbulence is analyzed through both temporal and spatial magnetic fluctuation spectra. A magnetically turbulent plasma is produced in the MHD wind tunnel configuration of the Swarthmore Spheromak Experiment. The power of magnetic fluctuations is projected into directions perpendicular and parallel to a local mean field; the ratio of these quantities shows the presence of variance anisotropy which varies as a function of frequency. Comparisons among magnetic, velocity, and density spectra are also made, demonstrating that the energy of the turbulence observed is primarily seeded by magnetic fields created during plasma production. Direct spatial spectra are constructed using multi-channel diagnostics and are used to compare to frequency spectra converted to spatial scales using the Taylor hypothesis. Evidence for the observation of dissipation due to ion inertial length scale physics is also discussed, as well as the role laboratory experiments can play in understanding turbulence typically studied in space settings such as the solar wind. Finally, all turbulence results are shown to compare fairly well to a Hall-MHD simulation of the experiment.

• OSTI ID: 22365488
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 790; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ANISOTROPY
DATA ANALYSIS
DENSITY
FLUCTUATIONS
FREQUENCY DEPENDENCE
HYPOTHESIS
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
MEAN-FIELD THEORY
PLASMA PRODUCTION
SIMULATION
SOLAR WIND
SPACE
SPECTRA
SPHEROMAK DEVICES
TURBULENCE