  The hydrogen Lyman lines ( 91.2 nm < lambda < 121.6 nm) are significant
contributors to the radiative losses of the solar chromosphere, and are
enhanced during flares. We have shown previously that the Lyman lines observed
by the Extreme Ultraviolet Variability instrument onboard the Solar Dynamics
Observatory exhibit Doppler motions equivalent to speeds on the order of 30
km/s. But contrary to expectation, no dominant flow direction was observed,
with both redshifts and blueshifts present. To understand the formation of the
Lyman lines, particularly their Doppler motions, we have used the radiative
hydrodynamic code, RADYN, and the radiative transfer code, RH, to simulate the
evolution of the flaring chromosphere and the response of the Lyman lines
during solar flares. We find that upflows in the simulated atmospheres lead to
blueshifts in the line cores, which exhibit central reversals. We then model
the effects of the instrument on the profiles using the EVE instrument's
properties. What may be interpreted as downflows (redshifted emission) in the
lines after they have been convolved with the instrumental line profile may not
necessarily correspond to actual downflows. Dynamic features in the atmosphere
can introduce complex features in the line profiles which will not be detected
by instruments with the spectral resolution of EVE, but which leave more of a
signature at the resolution of the Spectral Investigation of the Coronal
Environment (SPICE) instrument on Solar Orbiter.
