  Despite being the most prominent emission line in the solar spectrum, there
has been a notable lack of studies devoted to variations in Ly$\alpha$ emission
during solar flares in recent years. However, the few examples that do exist
have shown Ly$\alpha$ emission to be a substantial radiator of the total energy
budget of solar flares (on the order of 10%). It is also a known driver of
fluctuations in earth's ionosphere. The EUV Variability Experiment (EVE)
onboard the Solar Dynamics Observatory now provides broadband, photometric
Ly$\alpha$ data at 10 s cadence with its Multiple EUV Grating
Spectrograph-Photometer (MEGS-P) component, and has observed scores of solar
flares in the 5 years since it was launched. However, the MEGS-P time profiles
appear to display a rise time of tens of minutes around the time of the flare
onset. This is in stark contrast to the rapid, impulsive increase observed in
other intrinsically chromospheric features (H$\alpha$, Ly$\beta$, LyC, C III,
etc.). Furthermore, the emission detected by MEGS-P peaks around the time of
the peak of thermal soft X-ray emission, rather than during the impulsive phase
when energy deposition in the chromosphere - often assumed to be in the form of
nonthermal electrons - is greatest. Given that spectrally-resolved Ly$\alpha$
observations during flares from SORCE/SOLSTICE peak during the impulsive phase
as expected, this suggests that the atypical behaviour of MEGS-P data is a
manifestation of the broadband nature of the observations. This could imply
that other lines and/or continuum emission that becomes enhanced during flares
could be contributing to the passband. Users are hereby urged to exercise
caution when interpreting broadband Ly$\alpha$ observations of solar flares.
Comparisons have also been made with other broadband Ly$\alpha$ photometers
such as PROBA2/LYRA and GOES/EUVS-E.
