Nanoflare Diagnostics from Magnetohydrodynamic Heating Profiles

TL;DR

This study combines 3D MHD simulations with hydrodynamic modeling to investigate nanoflare heating in the solar corona, revealing limitations in current models to fully explain observed active region core emissions.

Contribution

It introduces a novel integrated modeling approach linking MHD and HD simulations to produce observable predictions for coronal heating by nanoflares.

Findings

Photospheric driving produces low-frequency nanoflare heating.

Current models cannot fully explain active region core observations.

Loops result from random energization of adjacent field line clusters.

Abstract

The nanoflare paradigm of coronal heating has proven extremely promising for explaining the presence of hot, multi-million degree loops in the solar corona. In this paradigm, localized heating events supply enough energy to heat the solar atmosphere to its observed temperatures. Rigorously modeling this process, however, has proven difficult, since it requires an accurate treatment of both the magnetic field dynamics and reconnection as well as the plasma's response to magnetic perturbations. In this paper, we combine fully 3D magnetohydrodynamic (MHD) simulations of coronal active region plasma driven by photospheric motions with spatially-averaged, time-dependent hydrodynamic (HD) modeling of coronal loops to obtain physically motivated observables that can be quantitatively compared with observational measurements of active region cores. We take the behavior of reconnected field lines from the MHD simulation and use them to populate the HD model to obtain the thermodynamic evolution of the plasma and subsequently the emission measure distribution. We find the that the photospheric driving of the MHD model produces only very low-frequency nanoflare heating which cannot account for the full range of active region core observations as measured by the low-temperature emission measure slope. Additionally, we calculate the spatial and temporal distributions of field lines exhibiting collective behavior, and argue that loops occur due to random energization occurring on clusters of adjacent field lines.