Magnetic Flux Transport by turbulent reconnection in astrophysical flows

TL;DR

This paper reviews how turbulent magnetic reconnection in astrophysical flows can efficiently transport magnetic flux, impacting star formation and dynamo processes, based on recent 3D MHD simulations.

Contribution

It introduces and discusses an alternative magnetic flux transport mechanism via turbulent reconnection, supported by recent simulation results.

Findings

Turbulent reconnection effectively decouples magnetic flux in star-forming regions.

Simulation results show efficient magnetic flux transport from dense cores to outskirts.

The mechanism may influence dynamo processes in stars and accretion disks.

Abstract

The role of MHD turbulence in astrophysical environments is still highly debated. An important question that permeates this debate is the transport of magnetic flux. This is particularly important, for instance, in the context of star formation. When clouds collapse gravitationally to form stars, there must be some magnetic flux transport. otherwise the new born stars would have magnetic fields several orders of magnitude larger than the observed ones. Also, the magnetic flux that is dragged in the late stages of the formation of a star can remove all the rotational support from the accretion disk that grows around the protostar. The efficiency of the mechanism which is often invoked to allow the transport of magnetic fields in the different stages of star formation, namely, the ambipolar diffusion, has been lately put in check. We here discuss an alternative mechanism for magnetic flux transport which is based on turbulent fast magnetic reconnection. We review recent results obtained from 3D MHD numerical simulations that indicate that this mechanism is very efficient for decoupling and transport magnetic flux from the inner denser regions to the outskirts of collapsing clouds in the different stages of star formation. We also discuss this mechanism in the context of dynamo processes and speculate that it can play a role both in the solar dynamo and in accretion disk dynamo processes.