Meadowcroft, Rebecca L. ; Narang, Nancy ; Berghmans, David ; Dominique, Marie ; Nakariakov, Valery M.

submitted to Philosophical Transactions A

Abstract: 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.

Keyword(s): EUI ; waves ; corona
Links: link
Funding: 3PRODSIDCEXPLOIT, 3PRODP2SOC/3PRODSIDCEXPLOIT, 3PRODP2SOC/3PRODSIDCEXPLOIT, 3PRODP2SOC