IRIS observations of the low-atmosphere counterparts of active region outflows

Abstract

Active region (AR) outflows have been studied in detail since the launch of \textit{Hinode}/EIS and are believed to provide a possible source of mass and energy to the slow solar wind. In this work, we investigate the lower atmospheric counterpart of AR outflows using observations from the \textit{Interface Region Imaging Spectrograph} (\textit{IRIS}). We find that the \textit{IRIS} \siiv, \cii\ and \mgii\ transition region (TR) and chromospheric lines exhibit different spectral features in the outflows as compared to neighboring regions at the footpoints ("moss") of hot AR loops. The average redshift of \siiv\ in the outflows region ($\approx$ 5.5~km s${}^{-1}$) is smaller than typical moss ($\approx$ 12--13 km~s${}^{-1}$) and quiet Sun ($\approx$ 7.5 km~s${}^{-1}$) values, while the \cii~line is blueshifted ($\approx$ -1.1--1.5 km~s${}^{-1}$), in contrast to the moss where it is observed to be redshifted by about $\approx$ 2.5 km~s${}^{-1}$. Further, we observe that the low atmosphere underneath the coronal outflows is highly structured, with the presence of blueshifts in \siiv\ and positive \mgii\ k2 asymmetries (which can be interpreted as signatures of chromospheric upflows) which are mostly not observed in the moss. These observations show a clear correlation between the coronal outflows and the chromosphere and TR underneath, which has not been shown before. Our work strongly suggests that these regions are not separate environments and should be treated together, and that current leading theories of AR outflows, such as the interchange reconnection model, need to take into account the dynamics of the low atmosphere.

References in corpus (15)

• Prevalence of Small-scale Jets from the Networks of the Solar Transition Region and Chromosphere
• Observing the Roots of Solar Coronal Heating - in the Chromosphere
• Dynamic Fibrils are driven by Magnetoacoustic Shocks
• Generation of Solar Spicules and Subsequent Atmospheric Heating
• 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?
• Two components of the coronal emission revealed by EUV spectroscopic observations
• The Unresolved Fine Structure Resolved - IRIS observations of the Solar Transition Region
• Element Abundances: A New Diagnostic for the Solar Wind
• Why Is Non-thermal Line Broadening of Spectral Lines in The Lower Transition Region of the Sun Independent of Spatial Resolution?
• Heating signatures in the disk counterparts of solar spicules in IRIS observations
• Recovering Thermodynamics from Spectral Profiles observed by IRIS: A Machine and Deep Learning Approach
• Observations and numerical models of solar coronal heating associated with spicules
• Tracking Solar Active Region Outflow Plasma from its Source to the near-Earth Environment
• The drivers of active region outflows into the slow solar wind
• On Doppler shift and its Center-to-Limb Variation in Active Regions in the Transition Region

Cited by in corpus (11)

• The European Solar Telescope
• Probing the physics of the solar atmosphere with the Multi-slit Solar Explorer (MUSE): I. Coronal Heating
• Upflows in the upper solar atmosphere
• A comparison of the active region upflow and core properties using simultaneous spectroscopic observations from IRIS and Hinode
• Coronal Abundances in an Active Region: Evolution and Underlying Chromospheric and Transition Region Properties
• The Formation and Lifetime of Outflows in a Solar Active Region
• Plasma Upflows Induced by Magnetic Reconnection Above an Eruptive Flux Rope
• Dynamics in the transition region beneath active region upflows viewed by IRIS
• A new view of the solar interface region from the Interface Region Imaging Spectrograph (IRIS)
• Active region upflows in various coronal structures and their coupling to the lower atmosphere
• Variation in the intensity ratio at each wavelength point of the Si iv 1394/1403 Å lines. Spectral diagnostics of a bifurcated eruption