The Primordial Origin Model of Magnetic Fields in Spiral Galaxies

TL;DR

This paper presents a model where primordial uniform magnetic fields evolve into complex magnetic configurations in spiral galaxies, influencing galactic structure and activity, supported by MHD simulations.

Contribution

It introduces a primordial-origin model for galactic magnetic fields, demonstrating their evolution into various configurations through MHD simulations and their impact on galaxy features.

Findings

Composite magnetic configurations can form from weak primordial fields.

Different magnetic configurations can coexist within a single galaxy.

Vertical fields can lead to jet formation toward the halo.

Abstract

We propose a primordial-origin model for the composite configurations of global magnetic fields in spiral galaxies. We show that uniform tilted magnetic field wound up into a rotating disk galaxy can evolve into composite magnetic configurations comprising bisymmetric spiral (S=BSS), axisymmetric spiral (A=ASS), plane-reversed spiral (PR), and/or ring (R) fields in the disk, and vertical (V) fields in the center. By MHD simulations we show that these composite galactic fields are indeed created from weak primordial uniform field, and that the different configurations can co-exist in the same galaxy. We show that spiral fields trigger the growth of two-armed gaseous arms. The centrally accumulated vertical fields are twisted and produce jet toward the halo. We find that the more vertical was the initial uniform field, the stronger is the formed magnetic field in the galactic disk.