NUMERICAL SIMULATIONS OF IMPULSIVELY EXCITED ACOUSTIC-GRAVITY WAVES IN A STELLAR ATMOSPHERE

We aim to consider impulsively-generated non-linear acoustic-gravity waves in a gravitationally-stratified stellar atmosphere. Two-dimensional hydrodynamic equations are solved numerically for an ideal plasma with a realistic temperature profile. The numerical results show that an initial pulse in vertical velocity excites a leading wave front which is followed by a dispersive wake, oscillating with a period close to the acoustic cut-off period P-ac of the chromosphere. Impulses launched deeper within a low region of the stellar atmosphere result in a wake of smaller Pac. They form quasi-periodic shocks traveling from the chromosphere to the corona. The interaction of the secondary ("rebound") shocks with the chromosphere-corona transition region generates vortex motions, which may play important role the transition region dynamics.