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Updated: Jun 14, 2026
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An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids
Published on: December 4, 2017
Dynamo onset as a first-order transition: lessons from a shell model for magnetohydrodynamics.
Ganapati Sahoo1, Dhrubaditya Mitra, Rahul Pandit
1Department of Physics, Centre for Condensed Matter Theory, Indian Institute of Science, Bangalore 560012, India. ganapati@physics.iisc.ernet.in
Summary
Dynamo action in magnetohydrodynamic (MHD) turbulence exhibits a nonequilibrium first-order phase transition. This transition, characterized by energy ratios, reveals a fractal dynamo boundary with hysteresis.
Area of Science:
- Plasma Physics
- Astrophysics
- Fluid Dynamics
Background:
- Dynamo theory explains magnetic field generation in conductive fluids.
- Understanding magnetohydrodynamic (MHD) turbulence is crucial for astrophysical phenomena.
- Previous models often simplified the complex interplay of magnetic and kinetic forces.
Purpose of the Study:
- To investigate dynamo action in a shell model of MHD turbulence.
- To explore the effects of varying magnetic Prandtl number (PrM) and magnetic Reynolds number (ReM).
- To characterize dynamo onset as a phase transition and map its stability diagram.
Main Methods:
- Systematic and high-resolution numerical simulations.
- Utilizing a shell model for MHD turbulence.
- Analyzing the ratio of magnetic to kinetic energies as an order parameter.
Main Results:
- Dynamo onset is identified as a nonequilibrium first-order phase transition.
- A stability diagram (nonequilibrium phase diagram) in the (PrM-1,ReM) plane was generated.
- The dynamo boundary exhibits fractal characteristics, with observed hysteresis and nucleation phenomena.
Conclusions:
- The study provides a novel perspective on dynamo onset as a phase transition.
- The fractal nature of the dynamo boundary and associated phenomena offer new avenues for research.
- The findings have implications for understanding magnetic field generation in various astrophysical contexts.
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