Signatures of impulsive localized heating in the temperature distribution of multi-stranded coronal loops

TL;DR

This study uses hydrodynamic simulations to explore how different impulsive and steady heating regimes affect the temperature distribution in multi-stranded coronal loops, revealing signatures like condensations and DEM variations.

Contribution

It demonstrates the impact of localized impulsive heating on coronal loop temperature structures and explains observed phenomena, highlighting the need for more realistic transition region modeling.

Findings

Condensation forms with impulsive localized heating when pulse cadence is short.

DEM peak is sensitive to pulse cadence time.

Simulations explain some observed loop properties but cannot fully reproduce DEM structures.

Abstract

We study the signatures of different coronal heating regimes on the differential emission measure (DEM) of multi-stranded coronal loops by means of hydrodynamic simulations. We consider heating either uniformly distributed along the loops or localized close to the chromospheric footpoints, in both steady and impulsive conditions. Our simulations show that condensation at the top of the loop forms when the localized heating is impulsive with a pulse cadence time shorter than the plasma cooling time, and the pulse energy is below a certain threshold. A condensation does not produce observable signatures in the global DEM structure. Conversely, the DEM coronal peak is found sensitive to the pulse cadence time. Our simulations can also give an explanation of the warm overdense and hot underdense loops observed by TRACE, SOHO and Yohkoh. However, they are unable to reproduce both the transition region and the coronal DEM structure with a unique set of parameters, which outlines the need for a more realistic description of the transition region.