Unravelling the components of a multi-thermal coronal loop using magnetohydrodynamic seismology

TL;DR

This study uses magnetohydrodynamic seismology to analyze coronal loops, revealing their multi-thermal, multi-stranded structure and uniform heating, advancing understanding of solar corona heating mechanisms.

Contribution

It provides the first direct observation and resolution of multi-thermal components in coronal loops using wave speeds and magnetic field extrapolations.

Findings

Revealed differential wave speeds indicating multi-thermal structure

Derived temperature variations confirming multi-stranded loops

Found evidence for uniform heating along the loop

Abstract

Coronal loops, constituting the basic building blocks of the active Sun, serve as primary targets to help understand the mechanisms responsible for maintaining multi-million Kelvin temperatures in the solar and stellar coronae. Despite significant advances in observations and theory, our knowledge on the fundamental properties of these structures is limited. Here, we present unprecedented observations of accelerating slow magnetoacoustic waves along a coronal loop that show differential propagation speeds in two distinct temperature channels, revealing the multi-stranded and multi-thermal nature of the loop. Utilizing the observed speeds and employing nonlinear force-free magnetic field extrapolations, we derive the actual temperature variation along the loop in both channels, and thus are able to resolve two individual components of the multi-thermal loop for the first time. The obtained positive temperature gradients indicate uniform heating along the loop, rather than isolated footpoint heating.