Signatures of dynamic fibrils at the coronal base: Observations from Solar Orbiter/EUI

TL;DR

This study presents the first clear detection of dynamic fibrils in the solar corona using high-resolution EUV images from Solar Orbiter, revealing their properties and suggesting they are hot tips of chromospheric fibrils.

Contribution

First unambiguous identification of coronal signatures of dynamic fibrils using high-resolution EUV data, linking chromospheric features to coronal observations.

Findings

Detected bright dot-like features moving in active regions

Features exhibit parabolic trajectories similar to chromospheric DFs

Measured properties match those of chromospheric DFs, indicating a connection.

Abstract

The solar chromosphere hosts a wide variety of transients, including dynamic fibrils (DFs) that are characterised as elongated, jet-like features seen in active regions, often through H$\alpha$ diagnostics. So far, these features have been difficult to identify in coronal images primarily due to their small size and the lower spatial resolution of the current EUV imagers. Here we present the first unambiguous signatures of DFs in coronal EUV data using high-resolution images from the Extreme Ultraviolet Imager (EUI) on board Solar Orbiter. Using the data acquired with the 174~{\AA} High Resolution Imager (HRI$_{EUV}$) of EUI, we find many bright dot-like features (of size 0.3-0.5 Mm) that move up and down (often repeatedly) in the core of an active region. In a space-time map, these features produce parabolic tracks akin to the chromospheric observations of DFs. Properties such as their speeds (14 km~s$^{-1}$), lifetime (332~s), deceleration (82 m~s$^{-2}$) and lengths (1293~km) are also reminiscent of the chromospheric DFs. The EUI data strongly suggest that these EUV bright dots are basically the hot tips (of the cooler chromospheric DFs) that could not be identified unambiguously before because of a lack of spatial resolution.