Properties of Sound-like waves as seen by multiple EUV imagers from space 2025-10

The Sun's outer atmosphere, the corona, is a plasma filled with magnetic fields in form of loops. These loops host different types of waves including the Slow magneto-acoustic waves which are sound-like waves that travel along these loops causing them to compress and expand. Studying how these waves lose energy helps to understand how the corona gets heated to millions of degrees—an unsolved mystery.

A major puzzle is that these waves fade away, or dampen, much faster than what theories can explain. A recent study added to this mystery by showing that two different instruments [ namely, the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory and the Extreme Ultraviolet Imager (EUI) onboard Solar Orbiter (SolO) ] measured different damping lengths for the same wave, suggesting the instruments themselves might be affecting the measurements.

This work investigates that possibility by observing the same loop in the solar active region AR 12712 (see Figure) with a different pair of instruments: the High-Resolution Coronal Imager (Hi-C 2.1) and the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO).

The results from this study indicate no significant difference in the wave properties measured by the two telescopes. The wave's oscillation period (about 3 minutes), propagation speed (around 47 km/s), and most importantly, its damping length (about 4,000 kilometers) were all consistent within uncertainties between both the datasets. This may suggest that instrumental effects on damping length may be specific to the SDO/AIA and SolO/EUI pair, which can only be confirmed through multiple such coordinated observations.

Figure : (a) Full field of view of Hi-C 2.1 observing the active region AR12712. The box marked by green dashed lines outlines the subfield region presented in the other two panels. (b) and (c) A zoomed-in view of the loop structures in the vicinity of the target structure as observed from Hi-C and AIA, respectively. The white curves marked in these panels represent the boundaries of the selected loop where propagating slow magneto-acoustic waves are found.

These results have been recently reported in The Astrophysical Journal, 987:57, 2025 July 1, issue, published by the American Astronomical Society.

The lead author, Suraj K. Tripathy, was a dual degree master’s student at IIST. His master’s thesis was jointly supervised by Dr. Krishna Prasad, Scientist at the Aryabhata Research Institute of Observational Sciences (ARIES), and Prof. Dipankar Banerjee, the Vice Chancellor of IIST. Prof. Banerjee was the Director of ARIES at the time the study was conducted.