The horizontal internetwork magnetic field: numerical simulations in comparison to observations with Hinode

TL;DR

This paper uses numerical simulations to study the properties of horizontal magnetic fields in the Sun's photosphere, comparing results with Hinode observations, and finds that horizontal fields are stronger and more prevalent at certain heights.

Contribution

It provides a detailed analysis of the height distribution and strength of horizontal magnetic fields in the solar photosphere through realistic simulations and polarimetric response calculations.

Findings

Horizontal magnetic fields peak around 500 km height in the photosphere.

Horizontal fields are 1.6 to 4.3 times stronger than vertical fields in simulations.

Convective overshooting influences the distribution and flux of horizontal magnetic fields.

Abstract

Observations with the Hinode space observatory led to the discovery of predominantly horizontal magnetic fields in the photosphere of the quiet internetwork region. Here we investigate realistic numerical simulations of the surface layers of the Sun with respect to horizontal magnetic fields and compute the corresponding polarimetric response in the Fe I 630 nm line pair. We find a local maximum in the mean strength of the horizontal field component at a height of around 500 km in the photosphere, where it surpasses the vertical component by a factor of 2.0 or 5.6, depending on the initial and boundary conditions. From the synthesized Stokes profiles we derive a mean horizontal field component that is, respectively, 1.6 and 4.3 times stronger than the vertical component. This is a consequence of both the intrinsically stronger flux density of, and the larger area occupied by the horizontal fields. We find that convective overshooting expels horizontal fields to the upper photosphere, making the Poynting flux positive in the photosphere, while this quantity is negative in the convectively unstable layer below it.