High spatial resolution FeXII observations of solar active region

Abstract

We use UV spectral observations of active regions with the Interface Region Imaging Spectrograph (IRIS) to investigate the properties of the coronal FeXII 1349.4A emission at unprecedented high spatial resolution (~0.33"). We find that by using appropriate observational strategies (i.e., long exposures, lossless compression), FeXII emission can be studied with IRIS at high spatial and spectral resolution, at least for high density plasma (e.g., post-flare loops, and active region moss). We find that upper transition region (moss) FeXII emission shows very small average Doppler redshifts (v_Dop ~3 km/s), as well as modest non-thermal velocities (with an average ~24 km/s, and the peak of the distribution at ~15 km/s). The observed distribution of Doppler shifts appears to be compatible with advanced 3D radiative MHD simulations in which impulsive heating is concentrated at the transition region footpoints of a hot corona. While the non-thermal broadening of FeXII 1349.4A peaks at similar values as lower resolution simultaneous Hinode/EIS measurements of FeXII 195A, IRIS observations show a previously undetected tail of increased non-thermal broadening that might be suggestive of the presence of subarcsecond heating events. We find that IRIS and EIS non-thermal line broadening measurements are affected by instrumental effects that can only be removed through careful analysis. Our results also reveal an unexplained discrepancy between observed 195.1/1349.4A FeXII intensity ratios and those predicted by the CHIANTI atomic database.

Accepted for publication on The Astrophysical Journal. 17 pages, 15 figures

References in corpus (14)

• CHIANTI - An atomic database for Emission Lines. Version 8
• Observing the Roots of Solar Coronal Heating - in the Chromosphere
• A publicly available simulation of an enhanced network region of the Sun
• Evidence of Non-Thermal Particles in Coronal Loops Heated Impulsively by Nanoflares
• High precision density measurements in the solar corona: I. Analysis methods and results for Fe XII and Fe XIII
• 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 multi-thermal and multi-stranded nature of coronal rain
• Observations of Active Region Loops with the EUV Imaging Spectrometer on Hinode
• Why Is Non-thermal Line Broadening of Spectral Lines in The Lower Transition Region of the Sun Independent of Spatial Resolution?
• Numerical Simulations of Coronal Heating through Footpoint Braiding
• Measurements of Non-Thermal Line Widths in Solar Active Regions
• Stellar Activity and Coronal Heating: an overview of recent results
• Hinode/Extreme-Ultraviolet Imaging Spectrometer Observations of the Temperature Structure of the Quiet Corona
• Doppler shift of hot coronal lines in a moss area of an active region

Cited by in corpus (33)

• The Multi-slit Approach to Coronal Spectroscopy with the Multi-slit Solar Explorer (MUSE)
• Probing the physics of the solar atmosphere with the Multi-slit Solar Explorer (MUSE): I. Coronal Heating
• Investigating the response of loop plasma to nanoflare heating using RADYN simulations
• Broad Non-Gaussian Fe XXIV Line Profiles in the Impulsive Phase of the 2017 September 10 X8.3 class Flare Observed by Hinode/EIS
• Non-Maxwellian analysis of the transition-region line profiles observed by the Interface Region Imaging Spectrograph
• The Heating of Solar Coronal Loops by Alfven Wave Turbulence
• IRIS observations of short-term variability in moss associated with transient hot coronal loops
• Stereoscopy of extreme UV quiet Sun brightenings observed by Solar Orbiter/EUI
• Observations and Modelling of the Pre-Flare Period of the 29 March 2014 X1 Flare
• IRIS observations of magnetic interactions in the solar atmosphere between pre-existing and emerging magnetic fields. II. UV emission properties
• The impact of multi-fluid effects in the solar chromosphere on the ponderomotive force under LTE and NEQ ionization conditions
• Magnetic loops above a small flux-emerging region observed by IRIS, Hinode and SDO
• Apparent and Intrinsic Evolution of Active Region Upflows
• Spectroscopic evidence of Alfvén wave damping in the off-limb solar corona
• Non-thermal line broadening due to braiding-induced turbulence in solar coronal loops
• Exploring the damping of Alfvén waves along a long off-limb coronal loop, up to 1.4 R${}_{\odot }$
• A new broadening technique of numerically unresolved solar transition region and its effect on the spectroscopic synthesis using coronal approximation
• Electron Densities in the Solar Corona Measured Simultaneously in the Extreme-Ultraviolet and Infra-Red
• Transient Formation of Loops in the Core of an Active Region
• A Statistical Study of IRIS Observational Signatures of Nanoflares and Non-thermal Particles
• Coronal Abundances in an Active Region: Evolution and Underlying Chromospheric and Transition Region Properties
• Quantifying the Influence of Key Physical Processes on the Formation of Emission Lines Observed by IRIS: I. Non-Equilibrium Ionization and Density-Dependent Rates
• Widespread Occurrence of High-Velocity Upflows in Solar Active Regions
• Non-thermal broadening of coronal lines in a 3D MHD loop model
• Investigating coronal wave energy estimates using synthetic non-thermal line widths
• The Transition Region of Solar Flare Loops
• Non-thermal motions and atmospheric heating of cool stars
• Are Non-thermal Velocities in Active Region Coronal Loops Anisotropic?
• On the Nature of Nonthermal Broadening of Spectral Lines Observed by IRIS
• A new view of the solar interface region from the Interface Region Imaging Spectrograph (IRIS)
• Pre-flare and active region plasma flows and structure seen by the short wavelength camera on SOLAR-C/EUVST
• Hard X-rays from the deep solar atmosphere. An unusual UV burst with flare properties
• A publicly available multi-observatory data set of an enhanced network patch from the Photosphere to Corona