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Diagnostics of MHD waves in the solar atmosphere is a topic which oftenencounters problems of interpretation, due partly to the high complexity of thesolar atmospheric medium. Forward modeling can significantly guideinterpretation, bridging the gap between numerical simulations andobservations, and increasing the reliability of mode identification forapplication of MHD seismology. In this work we aim at determining thecharacteristics of the fast MHD sausage mode in the corona on the modulation ofobservable quantities such as line intensity and spectral line broadening.Effects of line-of-sight angle, and spatial, temporal and spectral resolutionsare considered. We take a cylindrical tube simulating a loop in a low-{\beta}coronal environment with an optically thin background, and let it oscillatewith the fast sausage mode. A parametric study is performed. Among otherresults, we show that regardless of the ionisation state of the plasma, thevariation of spectral line broadening can be significant, even for lowintensity modulation. The nature of this broadening is not thermal but ismostly turbulent. This places spectrometers in clear advantage over imaginginstruments for the detection of the sausage mode. The modulation of allquantities is considerably affected by the line-of-sight angle, and especiallyby the spatial and temporal resolution when these are on the order of themode's wavelength and period. This places high constraints on instrumentation.

Line-of-sight geometrical and instrumental resolution effects on intensity perturbations by sausage modes