Abstract: Magnetic dynamos are a ubiquitous mechanism for growing, maintaining and structuring magnetic fields across many scales in the Universe. Small-scale dynamos, which most likely operate in almost all astrophysical plasma media, power and maintain the turbulent components of the magnetic field. These components then provide a reservoir of magnetic energy for large-scale dynamos, which, for example, build coherent, large-scale fields in accretion discs and spiral galaxies. In this talk, drawing on hundreds of numerical dynamo simulations across different plasma regimes, I will present a chronology of the different phases that a magnetic field undergoes when coupled to turbulence through the turbulent dynamo. I will focus on the differences between incompressible and compressible kinematic dynamos, with the latter remaining largely unexplored theoretically or numerically. I will argue that the kinematic dynamos we see in global simulations are artificially slow by orders of magnitude, whether in simulations of galaxies or merging neutron stars. I will also highlight some of our latest work on unravelling the more astrophysically relevant stages: dynamo back reaction and the fully nonlinear dynamo.

Faculty Host: Assistant Professor Muni Zhou

Zoom Link: https://dartmouth.zoom.us/j/99960465228