Evidence of Non-Thermal Particles in Coronal Loops Heated Impulsively by Nanoflares

TL;DR

This study presents high-resolution IRIS observations of coronal loop footpoints, supporting the presence of non-thermal electron beams generated by nanoflares, which significantly contribute to coronal heating and energy transfer.

Contribution

It provides observational evidence linking nanoflare-driven non-thermal electron beams to coronal heating, with new diagnostics for detecting these particles.

Findings

Rapid variability observed at loop footpoints (20-60s).

Consistency with simulations of non-thermal electron beam heating.

Constraints on properties of electron beams in the nonflaring corona.

Abstract

The physical processes causing energy exchange between the Sun's hot corona and its cool lower atmosphere remain poorly understood. The chromosphere and transition region (TR) form an interface region between the surface and the corona that is highly sensitive to the coronal heating mechanism. High resolution observations with the Interface Region Imaging Spectrograph (IRIS) reveal rapid variability (about 20 to 60 seconds) of intensity and velocity on small spatial scales at the footpoints of hot dynamic coronal loops. The observations are consistent with numerical simulations of heating by beams of non-thermal electrons, which are generated in small impulsive heating events called "coronal nanoflares". The accelerated electrons deposit a sizable fraction of their energy in the chromosphere and TR. Our analysis provides tight constraints on the properties of such electron beams and new diagnostics for their presence in the nonflaring corona.