Pns dynamo: Theory and observations

TL;DR

This paper reviews the turbulent mean-field dynamo mechanism in protoneutron stars, estimating magnetic field strengths during early evolution, and explores how initial rotation affects the resulting magnetic fields.

Contribution

It provides a theoretical estimate of magnetic field strengths generated by mean-field dynamo action in protoneutron stars with different initial rotation rates.

Findings

Strong magnetic fields (>3×10^{13} G) can be generated if initial rotation is rapid.

Moderate rotation leads to standard dipole fields with stronger small-scale surface fields.

Slow rotation results in no global magnetic field due to ineffective dynamo operation.

Abstract

We briefly review the turbulent mean-field dynamo action in protoneutron stars that are subject to convective and neutron finger instabilities during the early evolutionary phase. By solving the mean-field induction equation with the simplest model of $\alpha$-quenching we estimate the strength of the generated magnetic field. If the initial period of the protoneutron star is short, then the generated large-scale field is very strong ($> 3 \times 10^{13}$G) and exceeds the small-scale field at the neutron star surface, while if the rotation is moderate, then the pulsars are formed with more or less standard dipole fields ($< 3 \times 10^{13}$G) but with surface small-scale magnetic fields stronger than the dipole field. If rotation is very slow, then the mean-field dynamo does not operate, and the neutron star has no global field.