Generation of Seed Magnetic Field around First Stars:Effects of Radiation Force

TL;DR

This study models the generation of seed magnetic fields around the first stars, revealing that realistic unsteady conditions produce much weaker fields than previous steady-state predictions, with implications for early universe magnetism.

Contribution

It introduces an unsteady framework for magnetic field generation around first stars, showing smaller field strengths and highlighting the importance of photoionization over Thomson scattering.

Findings

Magnetic field strength is less than 10^{-19} G around first stars.

Steady assumptions overestimate magnetic field amplitudes.

Photoionization momentum transfer dominates over Thomson scattering.

Abstract

We investigate seed magnetic field generation in the early universe by radiation force of first stars. In the previous study with steady assumption, large amplitudes(10^{-15} G for first stars, 10^{-11}G for QSOs) are predicted. In this study, we formulate this issue in unsteady framework. Then, we consider a specific model of magnetic field generation around a very massive first star. Consequently, 1) we find steady assumption is not valid in realistic situation, and 2) obtain much smaller magnetic field strength than predicted by Langer et al. (2003). In addition, we find momentum transfer process during photoionization is more important than Thomson scattering. The resultant magnetic flux density around the first star is < 10^{-19}G. These seed magnetic field will not affect subsequent star formation in the neighbor of first stars.