Coronal microjets in quiet-Sun regions observed with the Extreme Ultraviolet Imager onboard Solar Orbiter

TL;DR

This study reports the discovery and analysis of the smallest coronal microjets in the quiet Sun, observed with high-resolution instruments onboard Solar Orbiter, revealing their properties, thermal nature, and likely magnetic reconnection origins.

Contribution

It provides the first detailed observations of microjets in the quiet Sun with high resolution, characterizing their physical properties and suggesting a magnetic reconnection formation mechanism.

Findings

Microjets have an average lifetime of 4.6 minutes.

They reach maximum lengths of 7.7 Mm and speeds of 62 km/s.

Their energies are comparable to nanoflare predictions.

Abstract

We report the smallest coronal jets ever observed in the quiet Sun with recent high resolution observations from the High Resolution Telescopes (HRI-EUV and HRI-Ly{\alpha}) of the Extreme Ultraviolet Imager (EUI) onboard Solar Orbiter. In the HRI-EUV (174 {\AA}) images, these microjets usually appear as nearly collimated structures with brightenings at their footpoints. Their average lifetime, projected speed, width, and maximum length are 4.6 min, 62 km s^(-1), 1.0 Mm, and 7.7 Mm, respectively. Inverted-Y shaped structures and moving blobs can be identified in some events. A subset of these events also reveal signatures in the HRI-Ly{\alpha} (H I Ly{\alpha} at 1216 {\AA}) images and the extreme ultraviolet images taken by the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory. Our differential emission measure analysis suggests a multi-thermal nature and an average density of ~1.4x10^9 cm^(-3) for these microjets. Their thermal and kinetic energies were estimated to be ~3.9x10^24 erg and ~2.9x10^23 erg, respectively, which are of the same order of the released energy predicted by the nanoflare theory. Most events appear to be located at the edges of network lanes and magnetic flux concentrations, suggesting that these coronal microjets are likely generated by magnetic reconnection between small-scale magnetic loops and the adjacent network field.