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Lookup NU author(s): Professor Anvar ShukurovORCiD
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© 2026 American Physical Society.The amplification of magnetic fields is crucial for understanding the observed magnetization of stars and galaxies. Turbulent dynamo is the primary mechanism responsible for that but the understanding of its action in a collapsing environment is still rudimentary and relies on limited numerical experiments. We develop an analytical framework and perform numerical simulations to investigate the behavior of small-scale and large-scale dynamos in a collapsing turbulent cloud. This approach is also applicable to expanding environments and facilitates the application of standard dynamo theory to evolving systems. Using a supercomoving formulation of the magnetohydrodynamic equations, we demonstrate that dynamo action in a collapsing background leads to a superexponential growth of magnetic fields in time, significantly faster than the exponential growth seen in stationary turbulence. The enhancement is mainly due to the increasing eddy turnover rate during the collapse, which boosts the instantaneous growth rate of the dynamo. We also show that the scaling of final saturated magnetic field strength with density robustly exceeds the expectation from considerations of pure flux-freezing. Apart from establishing a formal framework for studying magnetic field evolution in collapsing (or expanding) turbulent plasmas, these findings suggest that during star and galaxy formation magnetic fields can become dynamically relevant much earlier than previously thought.
Author(s): Irshad P M, Bhat P, Subramanian K, Shukurov A
Publication type: Article
Publication status: Published
Journal: Physical Review Letters
Year: 2026
Volume: 136
Issue: 9
Print publication date: 06/03/2026
Online publication date: 05/03/2026
Acceptance date: 13/01/2026
ISSN (print): 0031-9007
ISSN (electronic): 1079-7114
Publisher: American Physical Society
URL: https://doi.org/10.1103/fp1v-xrr5
DOI: 10.1103/fp1v-xrr5
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