  During solar flares, a large fraction of the released magnetic energy is
carried by energetic electrons that transfer and deposit energy in the Sun's
atmosphere. Electron transport is often approximated by a cold thick-target
model (CTTM), assuming that electron energy is much larger than the temperature
of the ambient plasma, and electron energy evolution is modeled as a systematic
loss. Using kinetic modeling of electrons, we re-evaluate the transport and
deposition of flare energy. Using a full collisional warm-target model (WTM),
we account for electron thermalization and for the properties of the ambient
coronal plasma such as its number density, temperature and spatial extent. We
show that the deposition of non-thermal electron energy in the lower atmosphere
is highly dependent on the properties of the flaring coronal plasma. In
general, thermalization and a reduced WTM energy loss rate leads to an increase
of non-thermal energy transferred to the chromosphere, and the deposition of
non-thermal energy at greater depths. The simulations show that energy is
deposited in the lower atmosphere initially by high energy non-thermal
electrons, and later by lower energy non-thermal electrons that partially or
fully thermalize in the corona, over timescales of seconds, unaccounted for in
previous studies. This delayed heating may act as a diagnostic of both the
injected non-thermal electron distribution and the coronal plasma, vital for
constraining flare energetics.
