Dust Battery: A Novel Mechanism for Seed Magnetic Field Generation in the Early Universe

TL;DR

This paper introduces a new dust battery mechanism that efficiently generates seed magnetic fields in the early universe, surpassing previous methods in effectiveness and scalability, with potential implications for cosmic magnetism.

Contribution

The authors propose a novel dust battery mechanism for seed magnetic field generation, demonstrating its effectiveness at low metallicities and its superiority over existing battery mechanisms.

Findings

Effective at metallicities around 10^{-5} Z_sun

Capable of producing seed fields of microgauss strength

Much more efficient than previous battery mechanisms

Abstract

We propose a novel dust battery mechanism for generating seed magnetic fields in the early universe, in which charged dust grains are radiatively accelerated, inducing strong electric currents that subsequently generate magnetic fields. Our analysis demonstrates that this process is effective even at very low metallicities (approximately $ \sim 10^{-5} Z_\odot$), and capable of producing seed fields with significant amplitudes of $B \sim \rm \mu G$ around luminous sources over timescales of years to Myr and across spatial scales ranging from au to kpc. Crucially, we find that this mechanism is generically $\sim10^8$ times more effective than the radiatively-driven electron battery or Biermann battery in relatively cool gas ($\ll 10^{5}\,$K), including both neutral and ionized gas. Furthermore, our results suggest that, to first order, dissipation effects do not appear to significantly impede this process, and that it can feasibly generate coherent seed fields on macroscopically large ISM scales (much larger than turbulent dissipation scales or electron mean-free-paths in the ISM). These seed fields could then be amplified by subsequent dynamo actions to the observed magnetic fields in galaxies. Additionally, we propose a sub-grid model for integration into cosmological simulations, and the required electric-field expressions for magnetohydrodynamic-particle-in-a-cell (MHD-PIC) simulations that explicitly model dust dynamics. Finally, we explore the broad applicability of this mechanism across different scales and conditions, emphasizing its robustness compared to other known battery mechanisms.