Regular Articles

Full Text / References

Non-Stationary Analysis of Plasma Turbulence-Zonal Flow Interactions Using Time-Varying Models

Fumikazu MIWAKEICHI¹⁾, Makoto SASAKI²⁾

1)

Department of Interdisciplinary Statistical Mathematics, The Institute of Statistical Mathematics, Tachikawa 190-8562, Japan

2)

College of Industrial Technology, Nihon University, Narashino 275-8575, Japan

(Received 28 January 2026 / Accepted 27 April 2026 / Published 8 July 2026)

Abstract

Understanding the interaction between plasma turbulence and zonal flow is essential for structure formation and transport regulation in magnetically confined plasmas. Using experimental data from the PANTA linear plasma device, we reduce the high-dimensional dynamics of numerous modes into two variables: turbulence and zonal. We then identify prominent intermittent bursts localized in the zonal-flow component—a phenomenon that, to the best of our knowledge, has not been reported previously. These bursts appear as impulsive, positive-going, low-frequency excursions superimposed on rapid background fluctuations. To address this non-stationarity, we investigate two approaches: a model-driven approach and a data-driven approach. We use a generalized Predator-Prey (P-P) model identified via an adaptive extended Kalman filter to track the evolution of time-varying physical parameters, and we also apply a Time-Varying Coefficient Vector Autoregressive model (TV-VAR) to achieve high-fidelity tracking of the sharp, transient burst dynamics. A distinct reorganization of the directed coupling structure is observed following burst events, including a transition to a regime in which zonal-flow regulation of turbulence becomes transiently dominant. These results indicate that time-varying interaction measures may provide informative features for burst forecasting and offer a basis for understanding regime transitions in transient plasma dynamics.

Copyright (c) 2026 The Japan Society of Plasma Science and Nuclear Fusion Research

Keywords

plasma turbulence, zonal flow, Predator-Prey model, Time-Varying Coefficient Vector Autoregressive (TV-VAR) model

DOI: 10.1585/pfr.21.1401038

Full Text

PDF format ([an error occurred while processing this directive]bytes)

References

• [1] T. Kobayashi et al., Phys. Plasmas 23, 102311 (2016).
• [2] S. Inagaki et al., Sci. Rep. 6, 22189 (2016).
• [3] T. Kobayashi et al., Plasma Fusion Res. 12, 1401019 (2017).
• [4] F. Miwakeichi and M. Sasaki, Phys. Plasmas 31, 082307 (2024).
• [5] S. Benkadda et al., Nucl. Fusion 41, 995 (2001).
• [6] M.A. Malkov et al., Phys. Plasmas 8, 5073 (2001).
• [7] E. Kim et al., Nucl. Fusion 43, 961 (2003).
• [8] Y. Kosuga et al., Phys. Plasmas 29, 122301 (2022).
• [9] P.H. Diamond et al., Plasma Phys. Control. Fusion 47, R35 (2005).
• [10] M. Sasaki et al., Plasma Phys. Control. Fusion 67, 095011 (2025).
• [11] J.C. Huang et al., Nucl. Fusion 66, 036010 (2026).
• [12] X. Jiang and G. Kitagawa, Signal Process. 33, 315 (1993).
• [13] T. Yamada et al., Rev. Sci. Instrum. 78, 123501 (2007).
• [14] R.K. Mehra, IEEE Trans. Autom. Control 17, 693 (1972).
• [15] H. Akaike, IEEE Trans. Autom. Control 19, 716 (1974).