# Siam Physics Congress 2015

May 20 – 22, 2015
Asia/Bangkok timezone
The Centennial Celebration of General Relativity Theory and 80 Years of Thai Physics Graduate

## Magnetic Field Line Random Walk in Isotropic Turbulence at Very High Kubo Number

May 21, 2015, 3:00 PM
15m
White Lotus

### White Lotus

Oral presentation Astronomy, Astrophysics, and Cosmology

### Speaker

Wirin Sonsrettee (Faculty of Engineering and Technology, Panyapiwat Institute of Management, Nonthaburi 11120, Thailand)

### Description

Most of the field line random walk (FLRW) theories proposed in the past were strongly influenced by studies of the limit of weak fluctuations. In this limit, the behavior of the FLRW can be characterized by the Kubo number $R=(b/B_0)(\ell_\parallel/\ell_\perp)$, where $b$ is the root mean squared fluctuation, $\ell_\parallel$ and $\ell_\perp$ are turbulence coherence scales parallel and perpendicular to the mean field $B_0$, respectively. In the case of $R \ll 1$, a quasi-1D limit, all theories and computer simulations agree that the FLRW is quasilinear. In the case of $R \gg 1$, a quasi-2D limit, there are strong trapping effects in which some field lines are trapped in topological structures. Then the Corrsin-based theory is less accurate. To study the FLRW at high $R$, while avoiding the topological effects in the quasi-2D limit at high $R$, we examine different versions of Corrsin-based theory in the limit $R \to \infty$ by taking $B0 \to 0$ for finite $b$ instead of taking $\ell_\parallel/\ell_\perp \to \infty$. Naturally, with $B_0 = 0$, the FLRW is completely isotropic. We test the theory by performing computer simulations of the FLRW. All Corrsin-based theoretical results agree with simulation results for the FLRW at $B_0=0$ ($R=\infty$). We conclude that the applicability of Corrsin-based theories is limited not by high $R$, but by quasi-two-dimensionality.

### Primary author

Wirin Sonsrettee (Faculty of Engineering and Technology, Panyapiwat Institute of Management, Nonthaburi 11120, Thailand)

### Co-authors

Prof. David Ruffolo (Department of Physics, Faculty of Science, Mahidol University, Bangkok 10400, Thailand) Mr Prachanda Subedi (Bartol Research Institute, University of Delaware, Newark, DE 19716) Prof. William Matthaeus (Bartol Research Institute, University of Delaware, Newark, DE 19716) Dr andrew Snodin (Department of Materials and Production Technology Engineering, Faculty of Engineering, King Mongkut’s University of Technology North Bangkok, Bangkok 10800, Thailand) Mr pat wongpan (Department of Physics, University of Otago, Dunedin 9016, New Zealand) Dr piyanate Chuychai (School of Science, Mae Fah Luang University, Chiang Rai 57100, Thailand)

### Presentation materials

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