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Coronal mass ejections (CMEs) are the largest-scale eruptive phenomena in thesolar system. Associated with enormous plasma ejections and energy release,CMEs have an important impact on the solar-terrestrial environment. Accuratepredictions of the arrival times of CMEs at the Earth depend on the precisemeasurements on their three-dimensional velocities, which can be achieved usingsimultaneous line-of-sight (LOS) and plane-of-sky (POS) observations. Besidesthe POS information from routine coronagraph and extreme ultraviolet (EUV)imaging observations, spectroscopic observations could unveil the physicalproperties of CMEs including their LOS velocities. We propose that spectralline asymmetries measured by Sun-as-a-star spectrographs can be used forroutine detections of CMEs and estimations of their LOS velocities during theirearly propagation phases. Such observations can also provide important cluesfor the detection of CMEs on other solar-like stars. However, few studies haveconcentrated on whether we can detect CME signals and accurately diagnose CMEproperties through Sun-as-a-star spectral observations. In this work, weconstructed a geometric CME model and derived the analytical expressions forfull-disk integrated EUV line profiles during CMEs. For different CMEproperties and instrumental configurations, full disk-integrated line profileswere synthesized. We further evaluated the detectability and diagnosticpotential of CMEs from the synthetic line profiles. Our investigations provideimportant constraints on the future design of Sun-as-a-star spectrographs forCME detections through EUV line asymmetries.

Can we detect coronal mass ejections through asymmetries of Sun-as-a-star extreme-ultraviolet spectral line profiles?