# The effects of numerical resolution, heating timescales and background heating on thermal non-equilibrium in coronal loops

## TL;DR

This study investigates how numerical resolution, heating timescales, and background heating influence thermal non-equilibrium in coronal loops, revealing that proper resolution and background heating levels are crucial for accurate modeling.

## Contribution

The paper introduces an approximate method to model the transition region, reducing computational costs while accurately capturing TNE behavior in coronal loop simulations.

## Key findings

- Inadequate resolution suppresses TNE cycles.
- An approximate method models the TR as a discontinuity, reducing computational cost.
- TNE is suppressed unless background heating is sufficiently small.

## Abstract

Thermal non-equilibrium (TNE) is believed to be a potentially important process in understanding some properties of the magnetically closed solar corona. Through one-dimensional hydrodynamic models, this paper addresses the importance of the numerical spatial resolution, footpoint heating timescales and background heating on TNE. Inadequate transition region (TR) resolution can lead to significant discrepancies in TNE cycle behaviour, with TNE being suppressed in under-resolved loops. A convergence on the periodicity and plasma properties associated with TNE required spatial resolutions of less than 2 km for a loop of length 180 Mm. These numerical problems can be resolved using an approximate method that models the TR as a discontinuity using a jump condition, as proposed by Johnston et al. (2017a,b). The resolution requirements (and so computational cost) are greatly reduced while retaining good agreement with fully resolved results. Using this approximate method we (i) identify different regimes for the response of coronal loops to time-dependent footpoint heating including one where TNE does not arise and (ii) demonstrate that TNE in a loop with footpoint heating is suppressed unless the background heating is sufficiently small. The implications for the generality of TNE are discussed.