Chromospheric Bubbles in Solar Flares

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−1. Their signatures are also visible in the wings of Ca ii 8542 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.