Observational signatures of the coronal kink instability with thermal conduction

TL;DR

This study uses numerical simulations to explore how thermal conduction affects the observable signatures of the kink instability in coronal loops, revealing that conduction blurs internal structures despite reducing maximum temperatures.

Contribution

It provides the first detailed analysis of observational signatures of the kink instability with thermal conduction included in 3D MHD simulations, based on parameters from actual observations.

Findings

Thermal conduction reduces maximum local temperature by up to an order of magnitude.

Inclusion of thermal conduction blurs internal loop structures in observations.

Different spectral lines are formed depending on the thermal conduction effects.

Abstract

It is known from numerical simulations that thermal conduction along magnetic field lines plays an important role in the evolution of the kink instability in coronal loops. This study presents the observational signatures of the kink instability in long coronal loops when parallel thermal conduction is included. The 3D nonlinear magnetohydrodynamic equations are solved numerically to simulate the evolution of a coronal loop that is initially in an unstable equilibrium. The loop has length 80 Mm, width 8 Mm and an initial maximum twist of Phi = 11.5 pi, where Phi is a function of the radius. The initial loop parameters are obtained from a highly twisted loop observed in the TRACE 171 A waveband. Synthetic observables are generated from the data. These observables include spatial and temporal averaging to account for the resolution and exposure times of TRACE images. Parallel thermal conduction reduces the maximum local temperature by up to an order of magnitude. This means that different spectral lines are formed and different internal loop structures are visible with or without the inclusion of thermal conduction. However, the response functions sample a broad range of temperatures. The result is that the inclusion of parallel thermal conductivity does not have as large an impact on observational signatures as the order of magnitude reduction in the maximum temperature would suggest; the net effect is a blurring of internal features of the loop structure.