Properties of slow magneto-acoustic waves observed simultaneously using Hi-C 2.1 and AIA

Abstract

Propagating slow magneto-acoustic waves are commonly observed in different coronal structures but are most prominent in active region fan loops. Their rapid damping with damping lengths of the order of a wavelength has been investigated in the past by several authors. Although different physical mechanisms have been proposed, significant discrepancies between the theory and observations remain. Recent high-resolution observations captured simultaneously by two different instruments reveal distinct damping lengths for slow magneto-acoustic waves although their passbands are similar. These results suggest a possible contribution of instrumental characteristics on the measurement of damping lengths. Here, we analyse the behavior of slow waves using a different pair of instruments in order to check the prevalence of such results. In particular, the cotemporal observations of active region NOAA AR12712 by the High-Resolution Coronal Imager (Hi-C 2.1) and the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) are utilised. The estimated oscillation periods of slow magneto-acoustic waves identified from these data are 2.7{\,}$\pm${\,}0.2{\,}min from SDO/AIA, and 2.8{\,}$\pm${\,}1.2{\,}min from Hi-C 2.1. The corresponding propagation speeds are found to be 46.0{\,}$\pm${\,}1.7{\,}km{\,}s$^{-1}$ and 48.1{\,}$\pm${\,}0.6{\,}km{\,}s$^{-1}$, respectively. Damping lengths were calculated by two different methods, the Phase Tracking Method (PTM) and the Amplitude Tracking Method (ATM). The obtained values from PTM are 4.0{\,}$\pm${\,}2.1{\,}Mm and 4.1{\,}$\pm${\,}0.3{\,}Mm while those from ATM are 3.4{\,}$\pm${\,}1.0{\,}Mm and 3.7{\,}$\pm${\,}0.1{\,}Mm, respectively, for the AIA and Hi-C data. Our results do not indicate any notable difference in damping lengths between these instruments.