Modeling the Line-of-Sight Integrated Emission in the Corona: Implications for Coronal Heating

TL;DR

This paper models the optically thin solar corona as a line-of-sight integration of many independently heated flux tubes, revealing distinct observational signatures of nanoflares and steady heating in EUV light curves.

Contribution

It introduces a new model accounting for LOS effects in coronal emission, highlighting how different heating mechanisms produce observable signatures.

Findings

Nanoflares produce detectable signatures in EUV light curves.

Steady heating results in distinct observational signatures.

LOS effects significantly influence interpretation of coronal heating data.

Abstract

One of the outstanding problems in all of space science is uncovering how the solar corona is heated to temperatures greater than 1 MK. Though studied for decades, one of the major difficulties in solving this problem has been unraveling the line-of-sight (LOS) effects in the observations. The corona is optically thin, so a single pixel measures counts from an indeterminate number (perhaps tens of thousands) of independently heated flux tubes, all along that pixel's LOS. In this paper we model the emission in individual pixels imaging the active region corona in the Extreme Ultraviolet. If LOS effects are not properly taken into account, erroneous conclusions regarding both coronal heating and coronal dynamics may be reached. We model the corona as a LOS integration of many thousands of completely independently heated flux tubes. We demonstrate that despite the superposition of randomly heated flux tubes, nanoflares leave distinct signatures in light curves observed with multi-wavelength and high time cadence data, such as those data taken with the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory. These signatures are readily detected with the time-lag analysis technique of Viall & Klimchuk (2012). Steady coronal heating leaves a different and equally distinct signature that is also revealed by the technique.