Highly Efficient Modeling of Dynamic Coronal Loops

TL;DR

The paper introduces EBTEL, a highly efficient 0D model for simulating coronal loop evolution, offering accuracy and flexibility that surpass earlier models while drastically reducing computational time.

Contribution

Development of EBTEL, a novel 0D model that accurately captures coronal loop plasma evolution with improved flexibility and efficiency over previous models.

Findings

EBTEL achieves excellent agreement with 1D hydro simulations.

It models both impulsive and gradual heating scenarios.

It significantly reduces computational time by four orders of magnitude.

Abstract

Observational and theoretical evidence suggests that coronal heating is impulsive and occurs on very small cross-field spatial scales. A single coronal loop could contain a hundred or more individual strands that are heated quasi-independently by nanoflares. It is therefore an enormous undertaking to model an entire active region or the global corona. Three-dimensional MHD codes have inadequate spatial resolution, and 1D hydro codes are too slow to simulate the many thousands of elemental strands that must be treated in a reasonable representation. Fortunately, thermal conduction and flows tend to smooth out plasma gradients along the magnetic field, so "0D models" are an acceptable alternative. We have developed a highly efficient model called Enthalpy-Based Thermal Evolution of Loops (EBTEL) that accurately describes the evolution of the average temperature, pressure, and density along a coronal strand. It improves significantly upon earlier models of this type--in accuracy, flexibility, and capability. It treats both slowly varying and highly impulsive coronal heating; it provides the differential emission measure distribution, DEM(T), at the transition region footpoints; and there are options for heat flux saturation and nonthermal electron beam heating. EBTEL gives excellent agreement with far more sophisticated 1D hydro simulations despite using four orders of magnitude less computing time. It promises to be a powerful new tool for solar and stellar studies.