Enthalpy-based Thermal Evolution of Loops: II. Improvements to the Model

TL;DR

This paper enhances the EBTEL 0D coronal loop model by incorporating gravitational stratification and improved radiative cooling, enabling faster and more accurate simulations of plasma response to impulsive heating events.

Contribution

The authors introduce new models for the transition region to corona radiation ratio, including gravitational effects and a physical cooling approach, improving EBTEL's accuracy.

Findings

Good agreement between EBTEL and 1D hydro code Hydrad.

Enhanced EBTEL accurately tracks plasma density during impulsive heating.

Model is suitable for rapid, large-scale parameter studies.

Abstract

This paper develops the zero-dimensional (0D) hydrodynamic coronal loop model "Enthalpy-based Thermal Evolution of Loops" (EBTEL) proposed by Klimchuk et al (2008), which studies the plasma response to evolving coronal heating, especially impulsive heating events. The basis of EBTEL is the modelling of mass exchange between the corona and transition region and chromosphere in response to heating variations, with the key parameter being the ratio of transition region to coronal radiation. We develop new models for this parameter that now include gravitational stratification and a physically motivated approach to radiative cooling. A number of examples are presented, including nanoflares in short and long loops, and a small flare. The new features in EBTEL are important for accurate tracking of, in particular, the density. The 0D results are compared to a 1D hydro code (Hydrad) with generally good agreement. EBTEL is suitable for general use as a tool for (a) quick-look results of loop evolution in response to a given heating function, (b) extensive parameter surveys and (c) situations where the modelling of hundreds or thousands of elemental loops is needed. A single run takes a few seconds on a contemporary laptop.