Evolution of a density enhancement in a stratified atmosphere with uniformvertical magnetic field

In this paper the evolution of a density enhancement under the effect of gr avity in a stratified atmosphere is considered in a 2D simulation. The stra tified atmosphere is chosen with a high-density photosphere, transition reg ion and low-density corona where the enhancement is added in non-equilibriu m to the corona. The atmosphere is also threaded with an initially uniform vertical magnetic field. If sufficiently strong, the magnetic field plays a n important role in the evolution of the density enhancement as it tries to gain equilibrium. It not only enables the density enhancement to maintain its shape as it falls, but if strong enough results in the density enhancem ent rebounding a number of times. Therefore both upward and downward veloci ties of the enhancement are obtained. In all cases the density enhancement is found to fail with speeds much less than the free-fall speed and can rem ain in the corona at least 11 times longer than a free-fall particle. The r elevance of the simulations to the solar atmosphere is then discussed.