Letter to the Editor

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

¹ Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
e-mail: smandal.solar@gmail.com
² School of Space Research, Kyung Hee University, Yongin, Gyeonggi 446-701, Republic of Korea
³ Physikalisch-Meteorologisches Observatorium Davos, World Radiation Center, 7260 Davos Dorf, Switzerland
⁴ ETH-Zürich, Wolfgang-Pauli-Str. 27, 8093 Zürich, Switzerland
⁵ Solar-Terrestrial Centre of Excellence – SIDC, Royal Observatory of Belgium, Ringlaan -3- Av. Circulaire, 1180 Brussels, Belgium
⁶ Université Paris-Saclay, CNRS, Institut d’Astrophysique Spatiale, 91405 Orsay, France
⁷ Skobeltsyn Institute of Nuclear Physics, Moscow State University, 119992 Moscow, Russia
⁸ UCL-Mullard Space Science Laboratory, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UK
⁹ Lockheed Martin Solar and Astrophysics Laboratory, Building 252, 3251 Hanover Street, Palo Alto, CA 94304, USA
¹⁰ Bay Area Environmental Research Institute, NASA Research Park, Mailstop 18-4, Moffett Field, CA 94035, USA
¹¹ CSIRO, Cnr Vimiera & Pembroke Roads, Marsfield, NSW 2122, Australia

Received: 10 November 2022
Accepted: 9 December 2022

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 Hα 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 extreme-ultraviolet (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 Å High Resolution Imager (HRI_EUV) of EUI, we find many bright dot-like features (with a size of 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.