Two components of the coronal emission revealed by EUV spectroscopic observations

Abstract

Recent spectroscopic observations have revealed the ubiquitous presence of blueward asymmetries of emission lines formed in the solar corona and transition region. These asymmetries are most prominent in loop footpoint regions, where a clear correlation of the asymmetry with the Doppler shift and line width determined from the single Gaussian fit is found. Such asymmetries suggest at least two emission components: a primary component accounting for the background emission and a secondary component associated with high-speed upflows. The latter has been proposed to play a vital role in the coronal heating process and there is no agreement on its properties. Here we slightly modify the initially developed technique of Red-Blue (RB) asymmetry analysis and apply it to both artificial spectra and spectra observed by the EUV Imaging Spectrometer onboard Hinode, and demonstrate that the secondary component usually contributes a few percent of the total emission, has a velocity ranging from 50 to 150 km s-1 and a Gaussian width comparable to that of the primary one in loop footpoint regions. The results of the RB asymmetry analysis are then used to guide a double Gaussian fit and we find that the obtained properties of the secondary component are generally consistent with those obtained from the RB asymmetry analysis. Through a comparison of the location, relative intensity, and velocity distribution of the blueward secondary component with the properties of the upward propagating disturbances revealed in simultaneous images from the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory, we find a clear association of the secondary component with the propagating disturbances.

19 figures, accepted by ApJ

References in corpus (6)

• Observing the Roots of Solar Coronal Heating - in the Chromosphere
• Flows and Non-thermal Velocities in Solar Active Regions Observed with the Extreme-ultraviolet Imaging Spectrometer on Hinode: A Tracer of Active Region Sources of Heliospheric Magnetic Fields?
• The Spectroscopic Signature of Quasi-periodic Upflows in Active Region Timeseries
• Observation of High-speed Outflow on Plume-like Structures of the Quiet Sun and Coronal Holes with SDO/AIA
• STEREO Observations of Quasi-Periodically Driven High Velocity Outflows in Polar Plumes
• First Stereoscopic Coronal Loop Reconstructions from Stereo Secchi Images

Cited by in corpus (35)

• Prevalence of Small-scale Jets from the Networks of the Solar Transition Region and Chromosphere
• Persistent Doppler shift oscillations observed with HINODE/EIS in the solar corona: spectroscopic signatures of Alfvenic waves and recurring upflows
• Frequency-dependent damping in propagating slow magneto-acoustic waves
• The Role of Type II Spicules in the Upper Solar Atmosphere
• Surges and Si IV bursts in the solar atmosphere. Understanding IRIS and SST observations through RMHD experiments
• Explosive events on sub-arcsecond scale in IRIS observations: a case study
• Upflows in the upper solar atmosphere
• Explosive events in active region observed by IRIS and SST/CRISP
• Sun-as-a-star spectroscopic observations of the line-of-sight velocity of a solar eruption on October 28, 2021
• Possible detection of coronal mass ejections on late-type main-sequence stars in LAMOST medium-resolution spectra
• Are Chromospheric Nanoflares a Primary Source of Coronal Plasma?
• Investigating the Transition Region Explosive Events and Their Relationship to Network Jets
• H-alpha features with hot onsets III. Fibrils in Lyman-alpha and with ALMA
• On the multi-threaded nature of solar spicules
• Solar Flare Arcade Modelling: Bridging the gap from 1D to 3D Simulations of Optically Thin Radiation
• Full velocities and propagation directions of coronal mass ejections inferred from simultaneous full-disk imaging and Sun-as-a-star spectroscopic observations
• Narrow-line-width UV bursts in the transition region above Sunspots observed by IRIS
• On the relation between transition region network jets and coronal plumes
• Can we detect coronal mass ejections through asymmetries of Sun-as-a-star extreme-ultraviolet spectral line profiles?
• IRIS observations of the low-atmosphere counterparts of active region outflows
• Evolution of active region outflows throughout an active region lifetime
• Two-fluid numerical model of chromospheric heating and plasma outflows in a quiet-Sun
• Contribution of spicules to solar coronal emission
• Plasma injection into a solar coronal loop
• The Formation and Lifetime of Outflows in a Solar Active Region
• Widespread Occurrence of High-Velocity Upflows in Solar Active Regions
• Spectroscopic observation of a transition region network jet
• Structure of sunspot light bridges in the chromosphere and transition region
• Plasma Upflows Induced by Magnetic Reconnection Above an Eruptive Flux Rope
• Propagating Oscillations in the Lower Atmosphere under Coronal Holes
• Signature and escape of highly fractionated plasma in an active region
• Electron density of active region outflows measured by the EUV Imaging Spectrometer onboard Hinode
• Population of Bright Plume Threads in Solar Polar Coronal Holes
• Line Profile Studies of Coronal Active Regions in Fe XII λ195.12 Using Hinode/EIS
• Active region upflows in various coronal structures and their coupling to the lower atmosphere