Stereoscopic observations reveal coherent morphology and evolution of solar coronal loops

TL;DR

This study uses stereoscopic observations from Solar Orbiter and SDO to analyze coronal loop morphology and evolution, revealing that loops are coherent, nearly circular, and exhibit synchronized intensity changes, supporting a monolithic plasma bundle model.

Contribution

First stereoscopic analysis of coronal loops showing their coherent, circular cross-section and synchronized intensity variations, challenging the 'coronal veil' hypothesis.

Findings

Coronal loops have nearly circular cross-sections.

Loops show coherent intensity variations over 30 minutes.

Results support the monolithic plasma bundle model.

Abstract

Coronal loops generally trace magnetic lines of force in the upper solar atmosphere. Understanding the loop morphology and its temporal evolution has implications for coronal heating models that rely on plasma heating due to reconnection at current sheets. Simultaneous observations of coronal loops from multiple vantage points are best suited for this purpose. Here, we report a stereoscopic analysis of coronal loops in an active region based on observations from the Extreme Ultraviolet Imager on board the Solar Orbiter Spacecraft and the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory. Our stereoscopic analysis reveals that coronal loops have nearly circular cross-sectional widths and that they exhibit temporally coherent intensity variations along their lengths on timescales of around 30\,minutes. Results suggest that coronal loops can be best represented as three-dimensional monolithic or coherent plasma bundles that outline magnetic field lines. Therefore, at least on the scales resolved by Solar Orbiter, it is unlikely that coronal loops are manifestations of emission from the randomly aligned wrinkles in two-dimensional plasma sheets along the line-of-sight as proposed in the `coronal veil' hypothesis.