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Date: Wednesday, October 14, 2026
Time: 09:00 UTC
Speaker: Dr. Frederick Gent
Affiliation: Aalto University / Stockholm University / Nordita
Title: The transitions between small-scale and large-scale dynamos in the interstellar medium
Abstract:
Magnetic fields play a critical role in the structure and evolution of galaxies, contributing equivalent typical energy to each of thermal, kinetic and cosmic ray energies in the interstellar medium (ISM). To acquire such strength, as observed, necessitates galactic dynamos which amplify the field at multiple scales in both time and space. The small-scale (or turbulent) dynamo (SSD) in the ISM acts fast within, at most, a few megayears and at scales smaller than that of the primary drivers of the turbulence (typically supernovae – SNe). Due to the multiphase structure of the ISM, spanning over seven orders of magnitude in temperature and the sporadic nature of SN forcing and heating, the dominant eigenmode of the SSD can shift between phases and over time. Comparison with simulations of numerically forced isothermal SSD and dynamo theory are therefore challenging.
The large-scale (or mean-field) dynamo (LSD) acts at kiloparsec scales and over timescales exceeding a gigayear. The primary driver is galactic shear aligning the turbulent magnetic field to its orbit. Simulations that have successfully modelled galactic LSD with mean-fields of strength and structure consistent with observed magnetic fields, typically have much weaker turbulent fields than observed. The LSD and SSD need to be present to effectively model how the galactic magnetic field arises of correct morphology and relative strength. We discuss our efforts to understand and quantify the actions and interactions of the SSD and LSD.
Date: Wednesday, November 4, 2026
Time: 09:00 UTC
Speaker: Dr. Catherine Hale
Affiliation: University of Edinburgh
Title:
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Date: Wednesday, November 25, 2026
Time: 09:00 UTC
Speaker: Dr. Vijay Mahatma
Affiliation: Cambridge University
Title:
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Date: Wednesday, December 16, 2026
Time: 09:00 UTC
Speaker: Dr. Yik Ki (Jackie) Ma
Affiliation: Max Planck Institute for Radio Astronomy
Title:
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Background image credit: NASA/ESA/CSA/STScI/SARAO; MeerKAT data from Heywood et al. (2022)
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