  We analyze a grid of radiative hydrodynamic simulations of solar flares to
study the energy balance and response of the atmosphere to nonthermal electron
beam heating. The appearance of chromospheric bubbles is one of the most
notable features that we find in the simulations. These pockets of
chromospheric plasma get trapped between the transition region and the lower
atmosphere as it is superheated by the particle beam. The chromospheric bubbles
are seen in the synthetic spectra, appearing as an additional component to
Balmer line profiles with high Doppler velocities as high as 200 km/s. Their
signatures are also visible in the wings of Ca II 8542A line profiles. These
bubbles of chromospheric plasma are driven upward by a wave front that is
induced by the shock of energy deposition, and require a specific heating rate
and atmospheric location to manifest.
