Göttingen 2025 – scientific programme

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EP: Fachverband Extraterrestrische Physik

EP 6: Sun and Heliosphere III

EP 6.2: Talk

Tuesday, April 1, 2025, 16:45–17:00, ZHG101

Robust yet rare coronal loops observed by EUI on board solar orbiter — •Vasantharaju Naganna and Hardi Peter — Max Planck Institute for Solar System Research, Göttingen, Germany

Coronal loops are the most common intensity features in the coronal filtergrams. However, their true nature and morphology are still debatable. By studying variations of cross-sectional properties along the loop and in time, we can understand the structure and heating of these loops. In this study, we investigated the cross-sectional intensity profiles, both spatially and temporally, of two unique coronal loops, observed in the periphery of two distinct active regions by the Extreme Ultraviolet Imager (EUI) on board Solar Orbiter. The main results of this study are 1. The lifetimes of these two loops (L1 > 120 min & L2 > 45 min) are longer than the typical coronal cooling timescales. 2. The loops exhibited an almost constant width, both spatially and temporally (width for L1 about 2.1 Mm, and for L2 about 1.3 Mm), indicating that the loops are stable cylindrical structures. 3. The loop widths are greater than 6-8 pixels of EUI, indicating that the loop cross-section is uniformly filled on well-resolvable scales. 4. We present observational evidence that the loops are not braided, which strongly suggests that the non-expanding nature of these loops with height cannot be attributed to the twist of the magnetic field lines. We conclude that these coronal loops are steady cylindrical structures of uniform cross section that exist for an unusually long time in the corona, which raises questions on which processes ensure the remarkable stability of these loops and our understanding of the coronal magnetic field structure.

Keywords: solar corona; coronal loops; active regions; coronal magnetic field; solar orbiter