Are Nanoflares Responsible for Coronal Heating?

TL;DR

This paper critically examines Parker's nanoflare hypothesis for coronal heating, questioning whether all current sheets formed by turbulence lead to reconnection and whether reconnection is the primary heating mechanism.

Contribution

It re-evaluates key assumptions of the nanoflare model, specifically the universality of reconnection in current sheets and their role in plasma heating.

Findings

Not all current sheets necessarily reconnect.

Turbulence may contribute to heating without reconnection.

Reconnection's role in heating is not conclusively established.

Abstract

Parker (1983) suggested a mechanism for the formation of current sheets (CSs) in the solar atmosphere. His main idea was that the tangling of coronal magnetic field lines by photospheric random flows facilitates the continuous formation of CSs in the solar atmosphere. This part of his idea represents one of the many ways by which the turbulent convection zone drives the formation of coherent structures and CSs in the solar atmosphere. Other mechanisms include emerging magnetic flux, interaction of current filaments, and explosive magnetic structures. However, there are two unproven assumptions in the initial idea of Parker for the coronal heating through nanoflares that must be re-examined. They are related to his suggestion that {ALL CSs formed are led to magnetic reconnection and that magnetic reconnection heats the plasma in the solar atmosphere. Let us discuss these two assumptions briefly in this short comment: (1) Are ALL coherent structures and CSs formed by the turbulent convection zone reconnecting? Does turbulence associated with non-reconnecting CSs play a role in the heating of the corona? (2) Does magnetic reconnection heat the plasma?