Solar Transition-Region Lines Observed by the Interface Region Imaging Spectrograph: Diagnostics for the O IV and Si IV Lines

Abstract

The formation of the transition-region O IV and Si IV lines observable by the Interface Region Imaging Spectrograph (IRIS) is investigated for both Maxwellian and non-Maxellian conditions characterized by a kappa-distribution exhibiting a high-energy tail. The \ion{Si}{4} lines are formed at lower temperatures than the O IV lines for all kappa. In non-Maxwellian situations with lower kappa, the contribution functions are shifted to lower temperatures. Combined with the slope of the differential emission measure, it is possible for the Si IV lines to be formed at very different regions of solar transition region than the O IV lines; possibly close to solar chromosphere. Such situations might be discernible by IRIS. It is found that photoexcitation can be important for the Si IV lines, but is negligible for the O IV lines. The usefulness of the O IV ratios for density diagnostics independently of kappa is investigated and it is found that the O IV 1404.78A /1399.77A ratio provides a good density diagnostics except for very low T combined with extreme non-Maxwellian situations.

The Astrophysical Journal Letters; accepted

References in corpus (1)

• Ultraviolet and extreme-ultraviolet line ratio diagnostics for O IV

Cited by in corpus (39)

• CHIANTI - An atomic database for Emission Lines. Version 8
• Hot Explosions in the Cool Atmosphere of the Sun
• Solar UV and X-Ray Spectral Diagnostics
• Slipping Magnetic Reconnection, Chromospheric Evaporation, Implosion, and Precursors in the 2014 September 10 X1.6-Class Solar Flare
• Solar ultraviolet bursts
• Are IRIS bombs connected to Ellerman bombs?
• Observations of Subarcsecond Bright Dots in the Transition Region above Sunspots with the Interface Region Imaging Spectrograph
• Simultaneous IRIS and Hinode/EIS observations and modelling of the 27 October 2014 X 2.0 class flare
• Non-Equilibrium Processes in the Solar Corona, Transition Region, Flares, and Solar Wind \textit{(Invited Review)}
• Si IV Resonance Line Emission During Solar Flares: Non-LTE, Non-equilibrium, Radiation Transfer Simulations
• KAPPA: A Package for Synthesis of optically thin spectra for the non-Maxwellian kappa-distributions based on the CHIANTI database
• Density diagnostics derived from the OIV and SIV intercombination lines observed by IRIS
• Non-Maxwellian analysis of the transition-region line profiles observed by the Interface Region Imaging Spectrograph
• IRIS and SDO observation of recurrent explosive events
• Ellerman bombs and UV bursts: reconnection at different atmospheric layers
• A closer look at a coronal loop rooted in a sunspot umbra
• Time Dependent Non-Equilibrium Ionization of Transition Region Lines Observed with IRIS
• IRIS Observations of Spicules and Structures Near the Solar Limb
• Imaging and Spectroscopic Observations of a Transient Coronal Loop: Evidence for the Non-Maxwellian $\kappa$-Distributions
• The EUV spectrum of the Sun: quiet and active Sun irradiances and chemical composition
• A Steady-state Supersonic Downflow in the Transition Region above a Sunspot Umbra
• Multi thermal atmosphere of a mini solar flare during magnetic reconnection observed with IRIS
• On the importance of the nonequilibrium ionization of Si IV and O IV and the line-of-sight in solar surges
• Modelling ion populations in astrophysical plasmas: carbon in the solar transition region
• Spectroscopic diagnostics of the non-Maxwellian $\kappa$-distributions using SDO/EVE observations of the 2012 March 7 X-class flare
• Solar surges related to UV bursts: Characterization through k-means, inversions and density diagnostics
• Determining Energy Balance in the Flaring Chromosphere from Oxygen V Line Ratios
• A benchmark study of atomic models for the transition region against quiet Sun observations
• A Statistical Study of IRIS Observational Signatures of Nanoflares and Non-thermal Particles
• Non-equilibrium ionization by a periodic electron beam. I. Synthetic coronal spectra and implications for interpretation of observations
• Non-equilibrium ionization by a periodic electron beam II. Synthetic Si IV and O IV transition region spectra
• Synthetic IRIS spectra of the solar transition region: Effect of high-energy tails
• Solar radio burst associated with the falling bright EUV blob
• Spectroscopic investigations of a filament reconnecting with coronal loops during a two-ribbon solar flare
• Multiwavelength Study of on-disk Coronal Hole Jets with IRIS and SDO observations
• The Transition Region of Solar Flare Loops
• CHIANTI -- an atomic database for emission lines -- Paper XVIII. Version 11, advanced ionization equilibrium models: density and charge transfer effects
• A new view of the solar interface region from the Interface Region Imaging Spectrograph (IRIS)
• Variation in the intensity ratio at each wavelength point of the Si iv 1394/1403 Å lines. Spectral diagnostics of a bifurcated eruption