Imaging and spectroscopic observations of extreme-ultraviolet brightenings using EUI and SPICE on board Solar Orbiter

Abstract

The smallest extreme-ultraviolet (EUV) brightening events that were detected so far, called campfires, have recently been uncovered by the High Resolution EUV telescope (HRIEUV), which is part of the Extreme Ultraviolet Imager (EUI) on board Solar Orbiter. HRIEUV has a broad bandpass centered at 17.4 nm that is dominated by Fe ix and Fe x emission at about 1 MK. We study the thermal properties of EUI brightening events by simultaneously observing their responses at different wavelengths using spectral data from the Spectral Imaging of the Coronal Environment (SPICE) also on board Solar Orbiter and imaging data from EUI. We studied three EUI brightenings that were identified in HRIEUV data that lie within the small areas covered by the slit of the SPICE EUV spectrometer. We obtained the line intensities of the spectral profiles by Gaussian fitting. These diagnostics were used to study the evolution of the EUI brightenings over time at the different line-formation temperatures. We find that (i) the detection of these EUI brightenings is at the limit of the SPICE capabilities. They could not have been independently identified in the data without the aid of HRIEUV observations. (ii) Two of these EUI brightenings with longer lifetimes are observed up to Ne viii temperatures (0.6 MK). (iii) All of the events are detectable in O vi (0.3 MK), and the two longer-lived events are also detected in other transition region (TR) lines. (iv) In one case, we observe two peaks in the intensity light curve of the TR lines that are separated by 2.7 min for C iii and 1.2 min for O vi. The Ne viii intensity shows a single peak between the two peak times of the TR line intensity. Spectral data from SPICE allow us to follow the thermal properties of EUI brightenings. Our results indicate that at least some EUI brightenings barely reach coronal temperatures.

13 pages, 16 figures, language editing, accepted in A&A

References in corpus (11)

• The Solar Orbiter mission -- Science overview
• Prevalence of Small-scale Jets from the Networks of the Solar Transition Region and Chromosphere
• Thermal Diagnostics with the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory: A Validated Method for Differential Emission Measure Inversions
• Transient small-scale brightenings in the quiet solar corona: a model for campfires observed with Solar Orbiter
• The magnetic drivers of campfires seen by the Polarimetric and Helioseismic Imager (PHI) on Solar Orbiter
• Extreme-ultraviolet bursts and nanoflares in the quiet-Sun transition region and corona
• Nanoflare distributions over solar cycle 24 based on SDO/AIA differential emission measure observations
• Capturing transient plasma flows and jets in the solar corona
• First observations from the SPICE EUV spectrometer on Solar Orbiter
• Propagating brightenings in small loop-like structures in the quiet Sun corona: Observations from Solar Orbiter/EUI
• Temperature of Solar Orbiter/EUI quiet Sun small scale brightenings: evidence for a cooler component

Cited by in corpus (9)

• First Perihelion of EUI on the Solar Orbiter mission
• EUV brightenings in the quiet-Sun: Signatures in spectral and imaging data from the Interface Region Imaging Spectrograph
• Spectroscopic evidence of cool plasma in quiet Sun HRIEUV small scale brightenings
• Small-scale magnetic flux emergence preceding a chain of energetic solar atmospheric events
• Thin coronal jets and plasmoid-mediated reconnection: Insights from Solar Orbiter observations and Bifrost simulations
• Extreme-ultraviolet transient brightenings in the quiet-Sun corona : Closest-perihelion observations with Solar Orbiter/EUI
• The nature of small scale EUV solar brightenings investigated as impulsive heating of short loops in 1D hydrododynamics simulations
• Investigating explosive events in a 3D quiet-Sun model: Transition region and coronal response
• Sulfur fractionation in coronal plumes as observed by Solar Orbiter/SPICE