The variety of scalar and vector fields in laboratory and nature plasmas is formed by plasma turbulence. Drift-wave fluctuations, driven by density gradients in magnetized plasmas, are known to relax the density gradient while they can generate flows. On the other hand, the sheared flow in the direction of magnetic fields causes Kelvin-Helmholtz type instabilities, which mix particle and momentum. These different types of fluctuations coexist in laboratory and nature, so that the multiple mechanisms for structural formation exist in extremely non-equilibrium plasmas. Here we report the discovery of a new order in plasma turbulence, in which chained structure formation is realized by cross-interaction between inhomogeneities of scalar and vector fields. The concept of cross-ferroic turbulence is developed, and the causal relation in the multiple mechanisms behind structural formation is identified, by measuring the relaxation rate and dissipation power caused by the complex turbulence-driven flux.

A new method is presented for identifying waveforms of fluctuations in turbulent plasmas. The method is based on heartbeat analysis in which the convolution of a waveform is obtained by employing the phase tracking method. Phase tracking is performed by correlating raw time-series data with a template waveform; the template is evaluated through iteration procedure. The method is applied to fluctuations in a PANTA plasma, and the nonlinear waveform and its distribution of periods are obtained. The identification of nonlinear waveforms is an essential task in the study of turbulent plasmas. The waveform, which includes information on higher harmonics (i.e., amplitude as well as phase), is the fundamental information that reflects nonlinearity in plasmas. A standard experimental approach is the convolution (i.e., conditional averaging) of time-series data. This approach has been applied to turbulent plasmas in the LMD-U device, and this has led to identification of large-amplitude solitary wave structures [1]. However, simple convolution within a prescribed period is not always sufficient because the period of oscillations can change over time. Intermittent variations in fluctuation periods, which often occur in turbulent plasmas, require a new method for identifying nonlinear waveforms.In this article, a new method is presented for identifying the waveforms of perturbations in turbulent plasmas. Convolution of a waveform is performed by employing the phase tracking method, which is based on heartbeat analysis [2]. The method is applied to fluctuations in PANTA plasmas [3], and the nonlinear waveform and its distribution of periods are obtained.At this point, we explain the new method. Figure 1 (a) illustrates a time series of observed fluctuations for a floating potential, which was observed in PANTA plasmas [1]. In this case, the perturbation is quasi-periodic, as can be

To study the nonlinear saturation mechanism in turbulent plasmas, we plan to obseve ion temperature gradient (ITG) modes in the Plasma Assembly for Nonlinear Turbulence Analysis (PANTA). Linear growth rates of ITG modes in the linear device are analyzed to determine their excitation conditions using a three-field fluid model to describe the ion motion. Parameter scans of the linear growth rate show the threshold for ITG mode excitation, and the typical plasma parameters of the PANTA are found in the unstable domain.

Meso-scale streamer has a radially elongated structure and is believed to enhance the radial transport. In order to study the control of the streamer, we demonstrated an end plate biasing to the streamer state in the PANTA linear plasma. During the end plate biasing, the electron density profile became more peaked, fluctuation was suppressed, the streamer structure was deconstructed, and the waveform became a periodic solitary state. The radial electric field only induced at around the end plate was found to play an important role for the streamer suppression.

Electron density (n e ) and electron temperature (T e ) measurements were performed via the plasma assembly for nonlinear turbulence analysis (PANTA) using the laser Thomson scattering technique. The second harmonic of Nd:YAG laser (λ = 532 nm) and an intensified charge-coupled device were used as a light source and a detector, respectively. Plasmas in PANTA were generated with Ar gas in a pressure range of 1 -5 mTorr. The range of the applied magnetic field was 600 -1500 G. At the center of the plasma, n e and T e ranged (4 -20) × 10 18 m −3 and 0.8 -3 eV, respectively. Further, n e monotonically increased and T e monotonically decreased with the increasing gas pressure and magnetic field.