Modeling X-ray Loops and EUV "Moss" in an Active Region Core

TL;DR

This study models steady heating in active region coronal loops to match observed X-ray and EUV moss intensities, introducing a new technique to constrain heating rates and analyze the physical parameters influencing emission.

Contribution

It presents a novel method to constrain coronal heating models using EUV footpoint intensities and explores the effects of loop expansion and filling factors on emission predictions.

Findings

Best agreement with observations achieved with 8% filling factor and expanding loops.

Simulated intensities differ from observed by up to 147%, indicating model limitations.

Heating rate scales with magnetic field strength and loop length as B^0.29 L^-0.95.

Abstract

The Soft X-ray intensity of loops in active region cores and corresponding footpoint, or moss, intensity observed in the EUV remain steady for several hours of observation. The steadiness of the emission has prompted many to suggest that the heating in these loops must also be steady, though no direct comparison between the observed X-ray and EUV intensities and the steady heating solutions of the hydrodynamic equations has yet been made. In this paper, we perform these simulations and simultaneously model the X-Ray and EUV moss intensities in one active regioncore with steady uniform heating. To perform this task, we introduce a new technique to constrain the model parameters using the measured EUV footpoint intensity to infer a heating rate. We find that a filling factor of 8% and loops that expand with height provides the best agreement with the intensity in two X-ray filters, though the simulated SXT Al12 intensity is 147% the observed intensity and the SXT AlMg intensity is 80% the observed intensity. From this solution, we determine the required heating rate scales as ${\bar{B}}^{0.29} L^{-0.95}$. Finally we discuss the future potential of this type of modeling, such as the ability to use density measurements to fully constrain filling factor, and its shortcomings, such as the requirement to use potential field extrapolations to approximate the coronal field.