Seed magnetic fields in turbulent small-scale dynamos

TL;DR

This study investigates how different seed magnetic field configurations influence small-scale dynamo action in turbulent astrophysical environments, finding that the dynamo's outcome is largely independent of seed field details and that initial seed information is lost.

Contribution

The paper demonstrates through simulations that seed field structure and strength do not affect the final magnetic fields generated by the small-scale dynamo, revealing the dynamo's insensitivity to initial conditions.

Findings

Magnetic field strength and properties are independent of seed field details.

Small-scale magnetic fields can be generated by tangling of large-scale fields even without dynamo action.

Memory of the seed field is lost in non-linear dynamo evolution.

Abstract

Magnetic fields in galaxies and galaxy clusters are amplified from a very weak seed value to the observed $\mu{\rm G}$ strengths by the turbulent dynamo. The seed magnetic field can be of primordial or astrophysical origin. The strength and structure of the seed field, on the galaxy or galaxy cluster scale, can be very different, depending on the seed-field generation mechanism. The seed field first encounters the small-scale dynamo, thus we investigate the effects of the strength and structure of the seed field on the small-scale dynamo action. Using numerical simulations of driven turbulence and considering three different seed-field configurations: 1) uniform field, 2) random field with a power-law spectrum, and 3) random field with a parabolic spectrum, we show that the strength and statistical properties of the dynamo-generated magnetic fields are independent of the details of the seed field. We demonstrate that, even when the small-scale dynamo is not active, small-scale magnetic fields can be generated and amplified linearly due to the tangling of the large-scale field. In the presence of the small-scale dynamo action, we find that any memory of the seed field for the non-linear small-scale dynamo generated magnetic fields is lost and thus, it is not possible to trace back seed-field information from the evolved magnetic fields in a turbulent medium.