2D cellular automaton model for the evolution of active region coronal plasmas

TL;DR

This paper presents a 2D cellular automaton model for coronal loop plasma evolution, linking magnetic stress release via nanoflares to plasma heating, and provides synthetic observational data to understand active region coronal heating.

Contribution

The study introduces a combined CA and EBTEL model that captures nanoflare energy distribution and plasma response, with scaling laws and synthetic data relevant for solar physics.

Findings

Nanoflares follow a power-law distribution with slope -2.5.

Repetition frequency of nanoflares increases with strand length.

Model reproduces observable signatures consistent with Hinode XRT data.

Abstract

We study a 2D cellular automaton (CA) model for the evolution of coronal loop plasmas. The model is based on the idea that coronal loops are made of elementary magnetic strands that are tangled and stressed by the displacement of their footpoints by photospheric motions. The magnetic stress accumulated between neighbor strands is released in sudden reconnection events or nanoflares that heat the plasma. We combine the CA model with the Enthalpy Based Thermal Evolution of Loops (EBTEL) model to compute the response of the plasma to the heating events. Using the known response of the XRT telescope on board Hinode we also obtain synthetic data. The model obeys easy to understand scaling laws relating the output (nanoflare energy, temperature, density, intensity) to the input parameters (field strength, strand length, critical misalignment angle). The nanoflares have a power-law distribution with a universal slope of -2.5, independent of the input parameters. The repetition frequency of nanoflares, expressed in terms of the plasma cooling time, increases with strand length. We discuss the implications of our results for the problem of heating and evolution of active region coronal plasmas.