Chromospheric counterparts of solar transition region unresolved fine structure loops

Abstract

Low-lying loops have been discovered at the solar limb in transition region temperatures by the Interface Region Imaging Spectrograph (IRIS). They do not appear to reach coronal temperatures, and it has been suggested that they are the long-predicted unresolved fine structures (UFS). These loops are dynamic and believed to be visible during both heating and cooling phases. Making use of coordinated observations between IRIS and the Swedish 1-m Solar Telescope, we study how these loops impact the solar chromosphere. We show for the first time that there is indeed a chromospheric signal of these loops, seen mostly in the form of strong Doppler shifts and a conspicuous lack of chromospheric heating. In addition, we find that several instances have a inverse Y-shaped jet just above the loop, suggesting that magnetic reconnection is driving these events. Our observations add several puzzling details to the current knowledge of these newly discovered structures; this new information must be considered in theoretical models.

5 pages, 3 figures, 2 movies; accepted for publication in A&A Letters

References in corpus (6)

• CRISP Spectropolarimetric Imaging of Penumbral Fine Structure
• Chromospheric Anemone Jets as Evidence of Ubiquitous Reconnection
• CRISPRED: A data pipeline for the CRISP imaging spectropolarimeter
• The Unresolved Fine Structure Resolved - IRIS observations of the Solar Transition Region
• 3D Temperature Mapping of Solar Photospheric Fine Structure Using Ca II H Filtergrams
• Properties and Modeling of Unresolved Fine Structure Loops Observed in the Solar Transition Region by IRIS

Cited by in corpus (8)

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• High-resolution observations of the solar photosphere, chromosphere and transition region. A database of coordinated IRIS and SST observations
• Evidence of multithermal nature of spicular downflows. Impact on solar atmospheric heating
• Small-scale loops heated to transition region temperatures and their chromospheric signatures in the simulated solar atmosphere
• The dynamic chromosphere: pushing the boundaries of observations and models
• The formation and heating of chromospheric fibrils in a radiation-MHD simulation
• On the Response of the Transition Region and the Corona to Rapid Excursions in the Chromosphere
• Small-scale dynamic phenomena associated with interacting fan-spine topologies: quiet-Sun Ellerman bombs, UV brightenings, and chromospheric inverted-Y-shaped jets