Solar Dynamics Observatory discovers thin high temperature strands in coronal active regions

TL;DR

This study uses Solar Dynamics Observatory data to confirm the presence of thin, high-temperature strands in coronal active regions, supporting impulsive heating models of the solar corona.

Contribution

It provides observational evidence for fine, high-temperature strands in active regions, validating models of impulsive heating in the solar corona.

Findings

High-temperature strands (>6 MK) are widely observed in active regions.

Fine structure in hot coronal loops supports impulsive heating scenarios.

Observations align with models predicting subarcsecond strand heating.

Abstract

One scenario proposed to explain the million degrees solar corona is a finely-stranded corona where each strand is heated by a rapid pulse. However, such fine structure has neither been resolved through direct imaging observations nor conclusively shown through indirect observations of extended superhot plasma. Recently it has been shown that the observed difference in appearance of cool and warm coronal loops (~1 MK, ~2-3 MK, respectively) -- warm loops appearing "fuzzier" than cool loops -- can be explained by models of loops composed of subarcsecond strands, which are impulsively heated up to ~10 MK. That work predicts that images of hot coronal loops (>~6 MK) should again show fine structure. Here we show that the predicted effect is indeed widely observed in an active region with the Solar Dynamics Observatory, thus supporting a scenario where impulsive heating of fine loop strands plays an important role in powering the active corona.