  When observing spectral lines in the optically-thin corona, line-of-sight
(LOS) effects can strongly affect the interpretation of the data, especially in
regions just above the limb. We present a semi-empirical forward model, called
GHOSTS, to characterize these effects. GHOSTS uses inputs from several other
models to compute non-equilibrium ionization states (which include the
solar-wind freezing-in effect) for many ions. These are used to generate
ensembles of simulated spectral lines that are examined in detail, with
emphasis on: (1) relationships between quantities derived from observables and
the radial variation of the observed quantities, (2) the behavior of thermal
and non-thermal components of the line width, and (3) relative contributions of
collisionally excited and radiatively scattered photons. We find that rapidly
changing temperatures in the low corona can cause ion populations to vary
dramatically with height. This can lead to line-width measurements that are
constant with height (a "plateau" effect) even when the temperature is
increasing rapidly, as the plane-of-sky becomes evacuated and the
foreground/background plasma dominates the observation. We find that LOS
effects often drive the velocity width to be close to the plane-of-sky value of
the wind speed, despite it flowing perpendicularly to the LOS there. The
plateau effect can also cause the non-thermal component of the line width to
greatly exceed the solar wind velocity at the observation height. Lastly, we
study how much of the LOS is significant to the observation, and the importance
of including continuum in the solar spectrum when computing the radiatively
scattered emission.
