  We investigate the processes that lead to the formation, ejection and fall of
a confined plasma ejection that was observed in a numerical experiment of the
solar corona. By quantifying physical parameters such as mass, velocity, and
orientation of the plasma ejection relative to the magnetic field, we provide a
description of the nature of this particular phenomenon. The time-dependent
three-dimensional magnetohydrodynamic (3D MHD) equations are solved in a box
extending from the chromosphere to the lower corona. The plasma is heated by
currents that are induced through field line braiding as a consequence of
photospheric motions. Spectra of optically thin emission lines in the extreme
ultraviolet range are synthesized, and magnetic field lines are traced over
time. Following strong heating just above the chromosphere, the pressure
rapidly increases, leading to a hydrodynamic explosion above the upper
chromosphere in the low transition region. The explosion drives the plasma,
which needs to follow the magnetic field lines. The ejection is then moving
more or less ballistically along the loop-like field lines and eventually drops
down onto the surface of the Sun. The speed of the ejection is in the range of
the sound speed, well below the Alfven velocity. The plasma ejection is
basically a hydrodynamic phenomenon, whereas the rise of the heating rate is of
magnetic nature. The granular motions in the photosphere lead (by chance) to a
strong braiding of the magnetic field lines at the location of the explosion
that in turn is causing strong currents which are dissipated. Future studies
need to determine if this process is a ubiquitous phenomenon on the Sun on
small scales. Data from the Atmospheric Imaging Assembly on the Solar Dynamics
Observatory (AIA/SDO) might provide the relevant information.
