Testing a Data-driven Active Region Evolution Model with Boundary Data at Different Heights from a Solar Magnetic Flux Emergence Simulation

TL;DR

This study evaluates a data-driven active region evolution model using boundary data at different heights from a solar flux emergence simulation, highlighting the impact of Lorentz force on model accuracy.

Contribution

It demonstrates that boundary data with lower Lorentz force at higher altitudes improves the DARE model's performance in simulating coronal magnetic fields.

Findings

Lorentz force significantly affects model accuracy.

Higher boundary levels yield better agreement with simulations.

Photospheric magnetic data can be suitable for driving the model.

Abstract

A data-driven active region evolution (DARE) model has been developed to study the complex structures and dynamics of solar coronal magnetic fields. The model is configured with typical coronal environment of tenuous gas governed by strong magnetic field, and thus its lower boundary is set at the base of the corona, but driven by magnetic fields observed in the photosphere. A previous assessment of the model using data from a flux emergence simulation (FES) showed that the DARE failed to reproduce the coronal magnetic field in the FES, which is attributed to the fact that the photospheric data in the FES has a very strong Lorentz force and therefore spurious flows are generated in the DARE model. Here we further test the DARE by using three sets of data from the FES sliced at incremental heights, which correspond to the photosphere, the chromosphere and the base of the corona. It is found that the key difference in the three sets of data is the extent of the Lorentz force, which makes the data-driven model perform very differently. At the two higher levels above the photosphere, the Lorentz force decreases substantially, and the DARE model attains results in much better agreement with the FES, confirming that the Lorentz force in the boundary data is a key issue affecting the results of the DARE model. However, unlike the FES data, the photospheric field from SDO/HMI observations has recently been found to be very close to force-free. Therefore, we suggest that it is still reasonable to use the photospheric magnetic field as approximation of the field at the coronal base to drive the DARE model.