Photospheric processes and magnetic flux tubes

TL;DR

This paper combines high-resolution observations and advanced 3D magnetohydrodynamic simulations to analyze small-scale magnetic flux concentrations, faculae physics, and the fundamental properties of magnetic flux tubes in the solar atmosphere.

Contribution

It provides new observational data and simulation results on magnetic flux tubes and faculae, enhancing understanding of their physical properties and stability conditions.

Findings

High-resolution observations of magnetic flux concentrations.

Simulations of flux tubes from the convection zone to the chromosphere.

Analysis of stability and equilibrium conditions of flux tubes.

Abstract

In the first part of these lecture notes, new high-resolution observations of small-scale magnetic flux concentrations are presented and compared to results from new three-dimensional magnetohydrodynamic simulations. Special attention is paid to the physics of faculae and to new three-dimensional radiation magnetohydrodynamic simulations of the integral layers from the top of the convection zone to the mid-chromosphere. The second part is devoted to a few basic properties of magnetic flux tubes, which can be considered to be an abstraction of the more complicated flux concentrations known from observations and numerical simulations. We treat electrical current sheets, the mechanical equilibrium condition at magnetic interfaces, the equations for constructing a magnetohydrostatic flux tube embedded in a gravitationally stratified atmosphere, the condition of radiative equilibrium, and the condition for interchange stability.