Observation of Turbulent Intermittency Scaling with Magnetic Helicity in an MHD Plasma Wind Tunnel

Schaffner, David; Wan, A.; Brown, M. R.

doi:10.1103/physrevlett.112.165001

Cited by 12 publications

(29 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Turbulence never absolutely reflects these symmetries, for example, the flow direction away from the Sun is special in the solar wind. We find that for the SSX plasma wind tunnel, [5][6][7][8] there are extended periods during which the turbulence is approximately stationary, homogeneous, and isotropic. The as yet unproven general ergodic theorem states that time averages are the same as ensemble averages, assuming the fluctuations are stationary (the ergodic theorem has been proven under certain conditions 9 ).…”

Section: Introductionmentioning

confidence: 95%

Magnetohydrodynamic turbulence: Observation and experiment

2015

View full text Add to dashboard Cite

We provide a tutorial on the paradigms and tools of magnetohydrodynamic (MHD) turbulence. The principal paradigm is that of a turbulent cascade from large scales to small, resulting in power law behavior for the frequency power spectrum for magnetic fluctuations E B ðf Þ. We will describe five useful statistical tools for MHD turbulence in the time domain: the temporal autocorrelation function, the frequency power spectrum, the probability distribution function of temporal increments, the temporal structure function, and the permutation entropy. Each of these tools will be illustrated with an example taken from MHD fluctuations in the solar wind. A single dataset from the Wind satellite will be used to illustrate all five temporal statistical tools. V C 2015 AIP Publishing LLC. [http://dx.

show abstract

Section: Introductionmentioning

confidence: 95%

Magnetohydrodynamic turbulence: Observation and experiment

2015

View full text Add to dashboard Cite

show abstract

“…TheḂ fluctuation signals for SSX were recorded by a 16-channel, three-direction, single-loop pickup coil probe array embedded in the midplane of the cylindrical wind tunnel, with a 65-MHz sampling rate and 14-bit dynamic range. By varying the amount of magnetic flux through the core of the gun, referred to here as "stuffing flux," the magnetic helicity of the injected plasma can be finely controlled [19]. Magnetic helicity corresponds to the degree of twistedness in the magnetic field, so varying injected helicity affects the resulting turbulent dynamics of the plasma as it evolves towards a relaxed Taylor state.…”

Section: Introductionmentioning

confidence: 99%

“…The solar wind is highly variable but there are two broad types: fast wind (V > 600 km/s) which is emitted from open coronal field lines and is typically low density (<5 protons/cm 3 ), has few large scale structures and has high amplitude but less developed turbulence, and slow wind, (V < 500 km/s) which is typically found in the ecliptic plane and originates from more complex coronal magnetic topology and is denser and more structured than the fast wind with more evolved but lower amplitude turbulence [26,27]. Here we use multiday long intervals of a fast wind stream (January [14][15][16][17][18][19][20][21]2008) and a slow wind stream (January [24][25][26][27][28][29]2010) with large scale magnetic fluctuations on the order of 10 nT.…”

Section: Introductionmentioning

confidence: 99%

“…The MHD wind tunnel configuration of the Swarthmore Spheromak Experiment (SSX) consists of a plasma gun which injects a spheromak of magnetized plasma into an ∼1-m-long cylindrical copper flux conserver [17]. Probes embedded in the chamber collect data on turbulent fluctuations inḂ as the plasma evolves down the length of the tube, eventually relaxing into a Taylor state [17][18][19][20]. After injection the plasma is completely dynamical, as there is no guide or vacuum field in the body of the chamber.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Permutation entropy and statistical complexity analysis of turbulence in laboratory plasmas and the solar wind

et al. 2015

View full text Add to dashboard Cite

. 2015. Permutation entropy and statistical complexity analysis of turbulence in laboratory plasmas and the solar wind. Phys. Rev. E 91, 023101.PHYSICAL REVIEW E 91, 023101 (2015) Permutation entropy and statistical complexity analysis of turbulence in laboratory plasmas and the solar wind The Bandt-Pompe permutation entropy and the Jensen-Shannon statistical complexity are used to analyze fluctuating time series of three different turbulent plasmas: the magnetohydrodynamic (MHD) turbulence in the plasma wind tunnel of the Swarthmore Spheromak Experiment (SSX), drift-wave turbulence of ion saturation current fluctuations in the edge of the Large Plasma Device (LAPD), and fully developed turbulent magnetic fluctuations of the solar wind taken from the Wind spacecraft. The entropy and complexity values are presented as coordinates on the CH plane for comparison among the different plasma environments and other fluctuation models. The solar wind is found to have the highest permutation entropy and lowest statistical complexity of the three data sets analyzed. Both laboratory data sets have larger values of statistical complexity, suggesting that these systems have fewer degrees of freedom in their fluctuations, with SSX magnetic fluctuations having slightly less complexity than the LAPD edge I sat . The CH plane coordinates are compared to the shape and distribution of a spectral decomposition of the wave forms. These results suggest that fully developed turbulence (solar wind) occupies the lower-right region of the CH plane, and that other plasma systems considered to be turbulent have less permutation entropy and more statistical complexity. This paper presents use of this statistical analysis tool on solar wind plasma, as well as on an MHD turbulent experimental plasma.

show abstract

“…327 Such magnetic relaxation of a spheromak plasma injected into a larger plasma volume also generates vigorous plasma turbulence, an approach exploited in the Swarthmore Spheromak Experiment (SSX ) wind tunnel to study MHD turbulence. 31,32,131,132 Magnetic self-organization also underlies the development of collimated astrophysical jets, where laboratory experiments have been used to generate and explore the evolution of magnetized plasma jets both at Caltech 310,326 and at the University of Washington. 328 Laser plasmas at the ELFIE laser facility at Ecole Polytechnique in France have also been used to produce scaled experiments of a collimated plasma outflow relevant to the physics of young stellar objects.…”

Section: F Self-organizationmentioning

confidence: 99%

Laboratory space physics: Investigating the physics of space plasmas in the laboratory

Howes

2018

Physics of Plasmas

View full text Add to dashboard Cite

Laboratory experiments provide a valuable complement to explore the fundamental physics of space plasmas without the limitations inherent to spacecraft measurements. Specifically, experiments overcome the restriction that spacecraft measurements are made at only one (or a few) points in space, enable greater control of the plasma conditions and applied perturbations, can be reproducible, and are orders of magnitude less expensive than launching spacecraft. Here I highlight key open questions about the physics of space plasmas and identify the aspects of these problems that can potentially be tackled in laboratory experiments. Several past successes in laboratory space physics provide concrete examples of how complementary experiments can contribute to our understanding of physical processes at play in the solar corona, solar wind, planetary magnetospheres, and outer boundary of the heliosphere. I present developments on the horizon of laboratory space physics, identifying velocity space as a key new frontier, highlighting new and enhanced experimental facilities, and showcasing anticipated developments to produce improved diagnostics and innovative analysis methods. A strategy for future laboratory space physics investigations will be outlined, with explicit connections to specific fundamental plasma phenomena of interest.

show abstract

Observation of Turbulent Intermittency Scaling with Magnetic Helicity in an MHD Plasma Wind Tunnel

Cited by 12 publications

References 34 publications

Magnetohydrodynamic turbulence: Observation and experiment

Magnetohydrodynamic turbulence: Observation and experiment

Permutation entropy and statistical complexity analysis of turbulence in laboratory plasmas and the solar wind

Laboratory space physics: Investigating the physics of space plasmas in the laboratory

Contact Info

Product

Resources

About