Spectroscopic Case Studies of Four Long-duration Transition-region Explosive Events

Abstract

This work presents a detailed spectroscopic case study of four long-duration transition-region (TR) explosive events (EEs) observed in NOAA Active Region 13213 on 2023 February 10 using the Interface Region Imaging Spectrograph. The dynamic spectral evolution of each event is tracked through multicomponent Gaussian fitting of the Si IV 1403 Å line profiles. Three recurrent spectral morphologies are identified and characterized: bilateral wing enhancement, exclusive red-wing enhancement, and exclusive blue-wing enhancement, among which bilateral enhancement is the most common in the studied cases. Throughout their lifetimes of 20-25 minutes, these events display sustained and evolving bidirectional flows, with high-velocity components ($|v|$ > 100 km $s^{-1}$) emerging in late phases. These spectral signatures are interpreted as evidence of ongoing or recurrent magnetic reconnection, where bilateral profiles correspond to bidirectional outflows, and exclusive wing enhancements represent geometric or evolutionary phases of the same process. In contrast, cotemporal flare ribbons and loop structures exhibit pronounced, unidirectional redshifts. This study underscores that significant non-Gaussian wing enhancement, rather than exclusively high speed, constitutes a defining spectroscopic signature of EEs, and provides detailed kinematic constraints on the dynamics of such TR EEs.

11 pages, 7 figures

References in corpus (22)

• The Interface Region Imaging Spectrograph (IRIS)
• Prevalence of Small-scale Jets from the Networks of the Solar Transition Region and Chromosphere
• On the prevalence of small-scale twist in the solar chromosphere and transition region
• Temporal evolution of chromospheric evaporation: case studies of the M1.1 flare on 2014 September 6 and X1.6 flare on 2014 September 10
• Multi-fluid simulations of chromospheric magnetic reconnection in a weakly ionized reacting plasma
• Iris si iv line profiles: An indication for the plasmoid instability during small-scale magnetic reconnection on the sun
• Observational Signatures of Simulated Reconnection Events in the Solar Chromosphere and Transition Region
• Simulations of small-scale explosive events on the Sun
• Explosive events on sub-arcsecond scale in IRIS observations: a case study
• Spectroscopic evidence for helicity in explosive events
• Explosive events in active region observed by IRIS and SST/CRISP
• Coronal hole boundaries at small scales: III. EIS and SUMER views
• IRIS and SDO observation of recurrent explosive events
• Explosive events associated with a surge
• IRIS Burst Spectra Co-Spatial To A Quiet-Sun Ellerman-Like Brightening
• Explosive events - swirling transition region jets
• Investigating the Transition Region Explosive Events and Their Relationship to Network Jets
• Magnetic Reconnection resulting from Flux Emergence: Implications for Jet Formation in the lower solar atmosphere?
• IRIS Si IV Line Profiles at Flare Ribbons as Indications of Chromospheric Condensation
• Signatures of quiet Sun reconnection events in Ca~{\sc ii}, H$\alpha$ and Fe~{\sc i}
• Signatures of transition region explosive events in hydrogen Ly-beta profiles
• Asymmetry of the spectral lines of the coronal hole and quiet Sun in the transition region