7826 20260803155622.0 SCART-2026-0069 Meadowcroft, Rebecca L. Decay Length of Slow MagnetoacousticWaves in the Solar Corona using SDO/AIA and Solo/EUI-HRIEUV 2026 Slow magnetoacoustic waves have been observed in the solar corona for decades; yet, existing theories do not fully explain the wide range of observed decay lengths, and measurements from different instruments frequently disagree. We present two events with simultaneous SDO/AIA and Solar Orbiter/EUI-HRIEUV observations of slow waves in sunspot-anchored coronal fan feathers. In Event 1, the LoS are separated by 16.2 degrees, while in Event 2, they are almost parallel. Using time-distance analysis, we identify waves with periods in the 3-minute band and quantify wave decay using the exponential folding length. When LoS are non-parallel, the ratio of decay lengths measured by the two instruments, λratio=λAIA/λEUI varies widely, with both λratio>1 and λratio<1 observed. However, when the LoS are almost parallel, the decay lengths agree with one another, and λratio≈1. These results show that the angle between the LoS and the wave propagation direction is key to determining the apparent decay of slow waves, a factor that has not yet been systematically accounted for. Since statistical studies of decay lengths constrain coronal energy-loss mechanisms, observational effects beyond simple projection must be corrected to reliably infer the underlying physical dissipation processes. 3PRODSIDCEXPLOIT, 3PRODP2SOC/ 3PRODSIDCEXPLOIT, 3PRODP2SOC/ 3PRODSIDCEXPLOIT, 3PRODP2SOC NO EUI waves corona Narang, Nancy Berghmans, David Dominique, Marie Nakariakov, Valery M. Philosophical Transactions A marie.dominique@ksb-orb.be https://arxiv.org/abs/2607.25509 submitted to REFERD