Magnetic field distribution in the quiet Sun: a simplified model approach

TL;DR

This paper presents a simplified numerical model simulating quiet Sun magnetic elements, producing a probability density function of magnetic field strengths that includes kG fields and matches observed properties.

Contribution

The study introduces a new simplified model that reproduces the distribution and evolution of quiet Sun magnetic fields, including the formation of kG magnetic strengths.

Findings

Magnetic fields up to 2 kG are produced within granulation timescales.

The model's stationary regime yields a mean unsigned flux density of 100 G.

The probability density function peaks at 30 G but has a secondary maximum at 2 kG.

Abstract

We simulate the dynamics and the evolution of quiet Sun magnetic elements to produce a probability density function of the field strengths associated with such elements. The dynamics of the magnetic field are simulated through a numerical model in which magnetic elements are passively driven by an advection field presenting spatio-temporal correlations which mimicks the granulation and the mesogranulation scales observed on the solar surface. The field strength can increase due to an amplification process which takes place where the magnetic elements converge. Starting from a delta-like probability density function centered on B=30 G, we obtain magnetic field strengths up to 2 kG (in absolute value). To derive the statistical properties of the magnetic elements several simulation runs are performed. The model is able to produce kG magnetic fields in a time interval of the order of the granulation time scale. The mean unsigned flux density and the mean magnetic energy density of the synthetic quiet Sun reach respectively 100 G and 350 G in the stationary regime. The derived probability density function of the magnetic field strength decreases rapidly from B=30 G to B=100 G and presents a secondary maximum for B=2 kG. From this result it follows that magnetic fields >700 G dominate the unsigned flux density and magnetic energy density although the probability density function of the field strength presents a maximum for B=30 G.