Magnetogenesis from Rotating Cosmic String Loops

TL;DR

This paper proposes a mechanism where rotating cosmic string loops induce plasma vortices that generate magnetic fields, which can be amplified to explain observed galactic magnetic fields.

Contribution

It introduces a novel process involving cosmic string loops for primordial magnetic field generation, incorporating detailed string network and loop dynamics modeling.

Findings

Generated magnetic fields are sufficient to explain galactic magnetic fields.

Magnetic fields are coherent and strong enough at decoupling for dynamo amplification.

The mechanism aligns with observed galactic magnetic field strengths.

Abstract

We present a mechanism to create vortices in a plasma via gravitational dragging behind rotating cosmic string loops. The vortical motions create magnetic fields by means of the Harrison-Rees mechanism; the fields are further enhanced through galactic collapse and dynamo amplification. Employing the Velocity dependent One Scale model (VOS) for the string network and incorporating loop dynamics, we compute the magnetic fields generated around the time of decoupling: these are just strong and coherent enough to account for presently observed magnetic fields in spiral galaxies if efficient dynamos with $\Gamma_{dy}^{-1}\approx 0.3$ Gyr are present.