  Coronal mass ejections (CMEs) are the largest-scale eruptive phenomena in the
solar system. Associated with enormous plasma ejections and energy release,
CMEs have an important impact on the solar-terrestrial environment. Accurate
predictions of the arrival times of CMEs at the Earth depend on the precise
measurements on their three-dimensional velocities, which can be achieved using
simultaneous line-of-sight (LOS) and plane-of-sky (POS) observations. Besides
the POS information from routine coronagraph and extreme ultraviolet (EUV)
imaging observations, spectroscopic observations could unveil the physical
properties of CMEs including their LOS velocities. We propose that spectral
line asymmetries measured by Sun-as-a-star spectrographs can be used for
routine detections of CMEs and estimations of their LOS velocities during their
early propagation phases. Such observations can also provide important clues
for the detection of CMEs on other solar-like stars. However, few studies have
concentrated on whether we can detect CME signals and accurately diagnose CME
properties through Sun-as-a-star spectral observations. In this work, we
constructed a geometric CME model and derived the analytical expressions for
full-disk integrated EUV line profiles during CMEs. For different CME
properties and instrumental configurations, full disk-integrated line profiles
were synthesized. We further evaluated the detectability and diagnostic
potential of CMEs from the synthetic line profiles. Our investigations provide
important constraints on the future design of Sun-as-a-star spectrographs for
CME detections through EUV line asymmetries.
