Solar coronal heating from small-scale magnetic braids

TL;DR

This study uses high-resolution Solar Orbiter observations to capture small-scale magnetic braids in the solar corona, demonstrating their role in impulsive and gentle magnetic reconnection that heats coronal plasma.

Contribution

First direct high-resolution imaging of small-scale magnetic braids in the solar corona, linking their untangling to impulsive heating events.

Findings

Coronal braids are more common over chromospheric filaments.

Magnetic reconnection occurs in both gentle and impulsive modes.

Untangling of braids correlates with impulsive heating episodes.

Abstract

Relaxation of braided coronal magnetic fields through reconnection is thought to be a source of energy to heat plasma in active region coronal loops. However, observations of active region coronal heating associated with an untangling of magnetic braids remain sparse. One reason for this paucity could be the lack of coronal observations with a sufficiently high spatial and temporal resolution to capture this process in action. Using new observations with high spatial resolution (250-270 km on the Sun) and high cadence (3-10 s) from the Extreme Ultraviolet Imager (EUI) on board Solar Orbiter, we observed the untangling of small-scale coronal braids in different active regions. The untangling is associated with impulsive heating of the gas in these braided loops. We assess that coronal magnetic braids overlying cooler chromospheric filamentary structures are perhaps more common. Furthermore, our observations show signatures of spatially coherent and intermittent coronal heating during the relaxation of the magnetic braids. Our study reveals the operation of gentle and impulsive modes of magnetic reconnection in the solar corona.