Modeling Evolving Coronal Loops with Observations from STEREO, Hinode, and TRACE

TL;DR

This study models coronal loops as multi-thread structures heated impulsively, successfully reproducing their observed lifetimes and densities, but facing challenges in matching high-temperature emission evolution.

Contribution

It applies a multi-thread hydrodynamic model to observations from multiple instruments, advancing understanding of coronal loop heating and cooling processes.

Findings

Reproduces observed loop lifetime and density with short energy release timescales.

Fails to match the evolution of very high temperature emission in XRT data.

Highlights potential issues in current understanding of post-reconnection cooling dynamics.

Abstract

The high densities, long lifetimes, and narrow emission measure distributions observed in coronal loops with apex temperatures near 1 MK are difficult to reconcile with physical models of the solar atmosphere. It has been proposed that the observed loops are actually composed of sub-resolution ``threads'' that have been heated impulsively and are cooling. We apply this heating scenario to nearly simultaneous observations of an evolving post-flare loop arcade observed with the EUVI/\textit{STEREO}, XRT/\textit{Hinode}, and \textit{TRACE} imagers and the EIS spectrometer on \textit{HINODE}. We find that it is possible to reproduce the extended loop lifetime, high electron density, and the narrow differential emission measure with a multi-thread hydrodynamic model provided that the time scale for the energy release is sufficiently short. The model, however, does not reproduce the evolution of the very high temperature emission observed with XRT. In XRT the emission appears diffuse and it may be that this discrepancy is simply due to the difficulty of isolating individual loops at these temperatures. This discrepancy may also reflect fundamental problems with our understanding of post-reconnection dynamics during the conductive cooling phase of loop evolution.