AWSoM Magnetohydrodynamic Simulation of a Solar Active Region with Realistic Spectral Synthesis

Abstract

Abstract For the first time, we simulate the detailed spectral line emission from a solar active region (AR) with the Alfvén Wave Solar Model (AWSoM). We select an AR appearing near disk center on 2018 July 13 and use the National Solar Observatory’s Helioseismic and Magnetic Imager synoptic magnetogram to specify the magnetic field at the model’s inner boundary. To resolve small-scale magnetic features, we apply adaptive mesh refinement with a horizontal spatial resolution of 0°.35 (4.5 Mm), four times higher than the background corona. We then apply the SPECTRUM code, using CHIANTI spectral emissivities, to calculate spectral lines forming at temperatures ranging from 0.5 to 3 MK. Comparisons are made between the simulated line intensities and those observed by Hinode/Extreme-ultraviolet Imaging Spectrometer where we find close agreement across a wide range of loop sizes and temperatures (about 20% relative error for both the loop top and footpoints at a temperature of about 1.5 MK). We also simulate and compare Doppler velocities and find that simulated flow patterns are of comparable magnitude to what is observed. Our results demonstrate the broad applicability of the low-frequency AWSoM for explaining the heating of coronal loops.