Transition region contribution to AIA observations in the context of coronal heating

TL;DR

This study uses hydrodynamic simulations and observations to analyze the contributions of the transition region and corona to AIA observations, emphasizing the importance of transition region in understanding coronal heating.

Contribution

It demonstrates the significant role of the transition region in AIA observations and links DEM slopes to intensity ratios, advancing coronal heating analysis methods.

Findings

Transition region brightness often exceeds coronal brightness in AIA channels.

Model and observed data show a correlation between DEM slope and intensity ratios.

Narrowband imaging sensitivity depends on heating parameters and transition region contributions.

Abstract

We investigate the relative contributions from the transition region and corona of coronal loops observed by the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO). Using EBTEL (Enthalpy-Based Thermal Evolution of Loops) hydrodynamic simulations, we model loops with multiple lengths and energy fluxes heated randomly by events drawn from power-law distributions with different slopes and minimum delays between events to investigate how each of these parameters influences observable loop properties. We generate AIA intensities from the corona and transition region for each realization. The variations within and between models generated with these different parameters illustrate the sensitivity of narrowband imaging to the details of coronal heating. We then analyze the transition region and coronal emission from a number of observed active regions and find broad agreement with the trends in the models. In both models and observations, the transition region brightness is significant, often greater than the coronal brightness in all six "coronal" AIA channels. We also identify an inverse relationship, consistent with heating theories, between the slope of the differential emission measure (DEM) coolward of the peak temperature and the observed ratio of coronal to transition region intensity. These results highlight the use of narrowband observations and the importance of properly considering the transition region in investigations of coronal heating.