Galactic magnetic fields may arise surprisingly fast, driven by collapsing plasma and turbulent flows.
How quickly can a galaxy develop organized magnetic fields that stretch across thousands of light-years? Traditional models suggest this process takes billions of years, yet observations of real galaxies point to much faster timelines.
A study published in Physical Review Letters offers a possible solution to this mismatch. The researchers propose that as plasma clouds collapse during galaxy formation, they can rapidly boost the growth of magnetic fields.
Most visible matter in the universe exists as plasma, a state that responds to forces such as gravity, temperature differences, and rotation. These forces can generate turbulence, and under such conditions, dynamo theory predicts that existing magnetic fields become stronger. This theory remains the main tool scientists use to explain how cosmic magnetic fields originate.
“However, dynamo theory has its limitations,” says Pallavi, an assistant professor at the International Centre for Theoretical Sciences (ICTS) and a co-author of the study. “In particular, it struggles to explain observations of young galaxies with robust magnetic fields across thousands of light-years.”
A New Perspective on Galaxy Formation
The study examines how dynamo processes might behave differently during the early stages of galaxy formation. It focuses on a collapsing cloud of ionized gas, a key step in building galaxies. “When the galaxy is forming, gravity itself can stir the plasma, which can amplify magnetic fields,” says Irshad, a graduate student at ICTS and the study’s lead author.
Using analytical methods, the researchers show that this gravity-driven motion can speed up the development of magnetic fields. Their results suggest that these fields could form much earlier than previously believed.
They link this effect to changes in turbulent motion during collapse. Turbulence creates swirling patterns called eddies, similar to currents in flowing water. The rate at which magnetic fields grow depends on how quickly these eddies rotate, known as the turnover rate.
As the cloud contracts, this turnover rate increases. The team found that this leads to “super exponential” growth in magnetic strength, offering a way to explain the strong magnetic fields seen in young galaxies. Their numerical results also indicate that these fields can become stronger than predictions based on standard dynamo theory.
Mathematical Framework and Limitations
To carry out their analysis, the researchers used a mathematical approach known as “supercomoving coordinates.” In cosmology, this method accounts for the expansion of the universe.
“These coordinates essentially make the equations of a collapsing galaxy the same as a static galaxy, making the calculations very straightforward,” says Irshad. “This works well for a uniformly collapsing spherical system, but we would need to extend this study for more realistic cases.”
Despite these insights, key questions remain. “There’s still much to learn in this ‘zeroth-order question you ask about the timescale’ too,” says Pallavi. Scientists are developing computational models to simulate how structures form in the universe, and this study provides predictions that could help test and refine those models.
Although magnetic forces are usually much weaker than gravity in shaping cosmic structures, the findings suggest that strong, ordered magnetic fields may have emerged earlier than expected. Over time, these fields may have played a subtle but lasting role in guiding the evolution of the universe.
Reference: “Turbulent Dynamos in a Collapsing Cloud” by Muhammed Irshad P., Pallavi Bhat, Kandaswamy Subramanian and Anvar Shukurov, 5 March 2026, Physical Review Letters.
DOI: 10.1103/fp1v-xrr5
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2 Comments
good
We are made of -star stuff- cosmic susceptibility.