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Related Experiment Video

Updated: May 11, 2026

A 100 KW Class Applied-field Magnetoplasmadynamic Thruster

A 100 KW Class Applied-field Magnetoplasmadynamic Thruster

Published on: December 22, 2018

Kinetic helicity needed to drive large-scale dynamos.

Simon Candelaresi¹, Axel Brandenburg

¹NORDITA, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-10691 Stockholm, Sweden.

Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics

|May 18, 2013

Summary

This summary is machine-generated.

Large-scale magnetic fields are generated by helical turbulence when the domain is large enough. The magnetic field energy grows linearly with helicity and scale ratio, provided a critical threshold is met.

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Uncoupling Coriolis Force and Rotating Buoyancy Effects on Full-Field Heat Transfer Properties of a Rotating Channel

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Area of Science:

Plasma physics
Astrophysical fluid dynamics
Magnetohydrodynamics

Background:

Large-scale magnetic field generation relies on the alpha effect in helical turbulence.
Turbulence must be helical and the domain large enough for the alpha effect to overcome diffusion.

Purpose of the Study:

Investigate the relationship between turbulence properties and large-scale magnetic field generation.
Clarify the influence of small-scale dynamo action on large-scale dynamo processes.
Examine dynamo action under specific forcing conditions (ABC flow).

Main Methods:

Three-dimensional turbulence simulations.
Analysis of saturated mean magnetic field energy.
Varying normalized helicity and scale ratios.

Main Results:

Mean magnetic field energy scales linearly with the product of normalized helicity and scale ratio above a critical value.
Large-scale dynamo action initiates when normalized helicity exceeds the inverse scale ratio.
Small-scale dynamo action does not impact large-scale dynamo behavior.

Conclusions:

The study quantifies the conditions for effective large-scale dynamo action.
Findings suggest previous minimal helicity estimates may be influenced by small-scale dynamo effects.
Alternative forcing methods (ABC flow) can lead to premature saturation and atypical field behavior.