# Turbulent dynamo in a weakly ionized medium

## TL;DR

This paper confirms through simulations that a new damping stage of turbulent dynamo occurs in weakly ionized media, affecting magnetic field growth and energy transfer in astrophysical plasmas.

## Contribution

First numerical confirmation of the damping stage of turbulent dynamo in weakly ionized media, validating theoretical predictions and exploring magnetic field evolution.

## Key findings

- Damping stage exhibits linear-in-time magnetic field growth.
- Magnetic field reaches turbulence injection scale after about eight eddy-turnover times.
- Weak ion-neutral coupling results in relatively weak magnetic fields.

## Abstract

The small-scale turbulent dynamo is an important process contributing to the cosmic magnetization. In partially ionized astrophysical plasmas, the dynamo growth of magnetic energy strongly depends on the coupling state between ions and neutrals and the ion-neutral collisional damping effect. A new damping stage of turbulent dynamo in a weakly ionized medium was theoretically predicted by Xu \& Lazarian (2016). By carrying out a 3D two-fluid dynamo simulation, here we for the first time numerically confirmed the physical conditions and the linear-in-time growth of magnetic field strength of the damping stage of dynamo. The dynamo-amplified magnetic field has a characteristic length as the damping scale, which increases with time and can reach the injection scale of turbulence after around eight largest eddy-turnover times given sufficiently low ionization fraction and weak initial magnetic field. Due to the weak coupling between ions and neutrals, most turbulent energy carried by neutrals cannot be converted to the magnetic energy, resulting in a relatively weak magnetic field at the end of dynamo. This result has important implications for the growth of magnetic fields in the partially ionized interstellar medium and shock acceleration of Galactic cosmic rays.