Magnetic Field Extrapolation in Active Region Well Comparable to Observations in Multiple Layers

Abstract

Magnetic field extrapolation is a fundamental tool to reconstruct the three-dimensional magnetic field above the solar photosphere. However, the prevalently used force-free field model might not be applicable in the lower atmosphere with non-negligible plasma β , where the crucial process of flux rope formation and evolution could happen. In this work, we perform extrapolation in active region 12158, based on a recently developed magnetohydrostatic (MHS) method that takes plasma forces into account. By comparing the results with those from the force-free field extrapolation methods, we find that the overall properties, which are characterized by the magnetic free energy and helicity, are roughly the same. The major differences lie in the magnetic configuration and the twist number of the magnetic flux rope (MFR). Unlike previous works either obtained sheared arcades or one coherent flux rope, the MHS method derives two sets of MFR, which are highly twisted and slightly coupled. Specifically, the result in the present work is more comparable to the high-resolution observations from the chromosphere, through the transition region to the corona, such as the filament fibrils, pre-eruptive braiding characteristics, and the eruptive double-J-shaped hot channel. Overall, our work shows that the newly developed MHS method is more promising to reproduce the magnetic fine structures that can well match the observations at multiple layers, and future data-driven simulation based on such extrapolation will benefit in understanding the critical and precise dynamics of flux rope before eruption.

Keywords

• Solar magnetic fields
• Solar active regions
• Solar extreme ultraviolet emission
• Solar corona
• Solar chromosphere
• Solar photosphere