Investigating the Effects of Atmospheric Stratification on Coronal Active Region Field Modelling

TL;DR

This study explores how including the chromosphere in magnetic field models of solar active regions affects eruption dynamics, revealing delays and increased energy release, and proposes simplified modeling adaptations.

Contribution

It demonstrates the significant impact of chromospheric stratification on eruption behavior and introduces simplified magnetofrictional model modifications to incorporate these effects.

Findings

Chromospheric stratification delays eruptions.

Increases magnetic energy released during eruptions.

Simplified models can effectively capture chromospheric effects.

Abstract

Understanding the evolution of the complex magnetic fields found in solar active regions is an active area of research. There are numerous models for such fields which range in their complexity due to the number of known physical effects included in them, the one common factor being they all extrapolate the field up from the photosphere. In this study we focus on the fact that, above the photosphere, and below the corona, lies the relatively cool and dense chromosphere -- which is often neglected in coronal models due to it being comparatively thin and difficult hard to model. We isolate and examine the effect including this boundary layer has on a 2.5D class of driven MHD models of an active region eruption. We find that it can result in significant changes to the dynamics of an erupting field far higher in the atmosphere than the chromosphere itself, generally delaying eruption and increasing the magnetic energy released in each eruption. We also test whether these effects can be approximated using a variation of the more computationally efficient magnetofrictional model, finding a number of simple adaptations of the standard magnetofrictional model capture the effect the chromospheric stratification well.