Spectroscopic evidence of cool plasma in quiet Sun HRIEUV small scale brightenings

Abstract

Context: A large number of the small and the short-lived EUV brightenings have been detected in the quiet Sun (QS) over the past three years, by the High Resolution Imager of the Extreme Ultraviolet Imager (HRIEUV) on board Solar Orbiter. It is still uncertain whether these events reach coronal temperatures, and thus if they directly participate to coronal heating. Aims: In this work, we evaluate the maximum temperature of 11 EUV brightenings in the QS, through plasma diagnostics involving UV/EUV spectroscopy and imaging. Methods: We use three QS observations coordinated between HRIEUV, the Spectral Imaging of the Coronal Environment (SPICE/Solar Orbiter), the EUV Imaging Spectrometer (EIS/Hinode), and the Atmospheric Imaging Assembly (AIA/SDO). We detected events in HRIEUV, ranging from 0.8 to 6.2 Mm in length. We then identified nine of them in SPICE and AIA, as well as three in EIS. We investigated their temporal evolution using their light curves, and applied temperature diagnostics, such as the LOCI Emission Measure (EM) and the differential EM (DEM). We also estimated the electron density of one event identified in EIS. Results: These events are dominated by emission of plasma at chromospheric and TR temperatures, and they barely reach temperatures above 1 MK. As such, we concluded that their contribution to coronal heating is not dominant. The estimated density of one of the event is n${}_e$ = (1.8 $\pm$ 1.3) $\times$ $10^{10}$ cm${}^{-3}$.

21 pages, 22 figures, accepted in A&A

References in corpus (29)

• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• The Solar Orbiter mission -- Science overview
• The chemical make-up of the Sun: A 2020 vision
• CHIANTI -- an atomic database for emission lines -- Paper XVI: Version 10, further extensions
• Key Aspects of Coronal Heating
• Coronal heating by MHD waves
• RHESSI Microflare Statistics II. X-ray Imaging, Spectroscopy & Energy Distributions
• High precision density measurements in the solar corona: I. Analysis methods and results for Fe XII and Fe XIII
• The Unresolved Fine Structure Resolved - IRIS observations of the Solar Transition Region
• The Solar Orbiter Science Activity Plan: translating solar and heliospheric physics questions into action
• Solar coronal heating from small-scale magnetic braids
• Evidence for Wave Heating of the Quiet Sun Corona
• The magnetic drivers of campfires seen by the Polarimetric and Helioseismic Imager (PHI) on Solar Orbiter
• Spectroscopy of very hot plasma in non-flaring parts of a solar limb active region: spatial and temporal properties
• First observations from the SPICE EUV spectrometer on Solar Orbiter
• First Perihelion of EUI on the Solar Orbiter mission
• Temperature of Solar Orbiter/EUI quiet Sun small scale brightenings: evidence for a cooler component
• Signatures of Steady Heating in Time Lag Analysis of Coronal Emission
• The Magnetic Properties of Heating Events on High-Temperature Active Region Loops
• Coronal heating and solar wind formation in quiet Sun and coronal holes: a unified scenario
• Imaging and spectroscopic observations of extreme-ultraviolet brightenings using EUI and SPICE on board Solar Orbiter
• EUV brightenings in the quiet-Sun: Signatures in spectral and imaging data from the Interface Region Imaging Spectrograph
• Search for photospheric footpoints of quiet Sun transition region loops
• On the Impulsive Heating of Quiet Solar Corona
• On the faintest solar coronal hard X-rays observed with FOXSI
• Transition region contribution to AIA observations in the context of coronal heating
• Quiet Sun electron densities and their uncertainties derived from spectral emission line intensities
• Comprehensive Determination of the Hinode/EIS Roll Angle
• On the ultraviolet signatures of small scale heating in coronal loops

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• Accessing the fine temporal scale of EUV brightenings and their quasi-periodic pulsations: 1 second cadence observations by Solar Orbiter/EUI
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