Thermodynamic Evolution of Flaring Loops with Nonlocal Thermal Transport

Abstract

Hot solar coronal loops, such as flaring loops, reach temperatures where the thermal transport becomes nonlocal. This occurs when the mean-free-path of electrons can no longer be assumed to be small. Using a modified version of the Lare2d code, we study the evolution of flare-heated coronal loops under three thermal transport models: classical Spitzer–Härm (SH), a flux-limited (FL) local model, and the nonlocal Schurtz–Nicolaï–Busquet (SNB) model. The SNB model is used extensively in laser-plasma studies. It has been benchmarked against accurate nonlocal Vlasov–Fokker–Planck models and proven to be the most accurate nonlocal model that can be applied on fluid timescales. Analysis of the density–temperature evolution cycles near the loop apex reveals a distinct evolutionary path for the SNB model, with higher temperatures and lower densities than local models. During energy deposition, the SNB model produces a more localized and intense temperature peak at the apex due to heat flux suppression, which also reduces chromospheric evaporation and results in lower postflare densities. Extreme-ultraviolet emission synthesis shows that the SNB model yields flare light curves with lower peak amplitudes and smoother decay phases. We also find that nonlocal transport affects equilibrium loop conditions, producing hotter and more rarefied apexes. These findings emphasize the need to account for nonlocal conduction in dynamic solar phenomena and highlight the potential of the SNB model for improving the realism of flare simulations. FL conduction models cannot reproduce the results of nonlocal transport covered by the SNB model.