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Forward-modeling the emission properties in various passbands is importantfor confidently identifying magnetohydrodynamic waves in the structured solarcorona. We examine how Non-equilibrium Ionization (NEI) affects the ExtremeUltraviolet (EUV) emissions modulated by standing fast sausage modes (FSMs) incoronal loops, taking the Fe IX 171 \AA\ and Fe XII 193 \AA\ emission lines asexamples. Starting with the expressions for linear FSMs in straight cylinders,we synthesize the specific intensities and spectral profiles for the twospectral lines by incorporating the self-consistently derived ionic fractionsin the relevant contribution functions. We find that relative to the case whereEquilibrium Ionization (EI) is assumed, NEI considerably impacts the intensitymodulations, but shows essentially no effect on the Doppler velocities orwidths. Furthermore, NEI may affect the phase difference between intensityvariations and those in Doppler widths for Fe XII 193 \AA\ when theline-of-sight is oblique to the loop axis. While this difference is $180^\circ$when EI is assumed, it is $\sim 90^\circ$ when NEI is incorporated for theparameters we choose. We conclude that in addition to viewing angles andinstrumental resolutions, NEI further complicates the detection of FSMs inspectroscopic measurements of coronal loops in the EUV passband.

Non-equilibrium Ionization Effects on Extreme-Ultraviolet Emissions Modulated by Standing Sausage Modes in Coronal Loops