Coventry University researchers recreate extreme planetary and stellar turbulence in lab experiments

Researchers have successfully recreated a long-theorised form of turbulence found deep inside planets and stars, providing new insights into how these distant worlds and our own planet generate heat, movement and magnetic fields.

An international team of scientists including Susanne Horn at Coventry University’s Research Centre for Fluid and Complex Systems, demonstrated, for the first time in a desktop-sized laboratory experiment, a special type of turbulent fluid motion known as diffusivity-free turbulence.

The findings validate decades of theoretical predictions and could help researchers better understand the hidden processes taking place inside Earth, Jupiter, the Sun and other celestial bodies.

The study, also involving academics at the University of California Los Angeles, Princeton Plasma Physics Laboratory, the Helmholtz-Zentrum Dresden-Rossendorf and the University of Colorado Boulder, focused on turbulent rotating convection, the movement of fluid caused by heating from below and cooling from above while the system rotates.

This process occurs naturally in the interiors of planets and stars, where it drives powerful currents and helps create global magnetic fields.

Until now, scientists have struggled to reproduce the most extreme form of this turbulence in a laboratory. Traditional experiments are affected by friction at the boundaries of the vessel, which throttles the energy transfer through the system, making it difficult to obtain the behaviour expected in large natural systems.

To overcome this challenge, the research team used liquid gallium, a metal that remains liquid near room temperature, inside a rotating experimental device. Rather than relying on conventional convection patterns, the researchers exploited a unique style of rotating convection known as oscillatory convection that arises exclusively in so-called low-Prandtl-number fluids, such as ionised hydrogen (plasma) and liquid metals.

The former is found inside stars; the latter is found inside planets and is also accessible in the lab. Oscillatory convection is largely controlled by conditions within the fluid itself and is less influenced by the walls of the container.

The team measured three key indicators of fluid behaviour: heat transfer, flow speed and internal temperature variations. Across all three measurements, the results closely matched long-standing theoretical predictions, while additional computer simulations independently confirmed the findings.

The experiments showed that this elusive “diffusivity-free” regime can exist even in relatively small laboratory systems, opening new opportunities for studying the extreme environments found deep inside planets and stars.

Lead researchers say the work provides important confidence that laboratory experiments can be used to model processes occurring even millions of miles away. By confirming the underlying physics, scientists can more reliably apply laboratory results to understanding planetary interiors, stellar convection and the generation of magnetic fields throughout the universe.

The breakthrough also establishes a new experimental platform for investigating the turbulent flows that shape the evolution of planets and stars, helping bridge the gap between theoretical models and observations of the natural world.

Find out more about Coventry University’s Research Centre for Fluid and Complex Systems.

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This work was published in Physical Review Letters: https://doi.org/10.1103/pc8y-j7g8 and is an Editors’ suggestion.

The academics involved in this paper are Jewel Abbate and Jonathan Aurnou from the University of California, Los Angeles; Yufan Xu from Princeton Plasma Physics Laboratory; Tobias Vogt from the Helmholtz-Zentrum Dresden-Rossendorf; Keith Julien from the University of Colorado Boulder; and Susanne Horn at Coventry University’s Research Centre for Fluid and Complex Systems.