  The magnetic configuration hosting prominences and their surrounding coro-
nal structure is a key research topic in solar physics. Recent theoretical and
observational studies strongly suggest that a helical magnetic flux rope is an
es- sential ingredient to fulfill most of the theoretical and observational
requirements for hosting prominences. To understand flux rope formation details
and obtain magnetic configurations suitable for future prominence formation
studies, we here report on three-dimensional isothermal magnetohydrodynamic
simulations including finite gas pressure and gravity. Starting from a
magnetohydrostatic corona with a linear force-free bipolar magnetic field, we
follow its evolution when introducing vortex flows around the main polarities
and converging flows towards the polarity inversion line near the bottom of the
corona. The con- verging flows bring feet of different loops together at the
polarity inversion line and magnetic reconnection and flux cancellation
happens. Inflow and outflow signatures of the magnetic reconnection process are
identified, and the thereby newly formed helical loops wind around pre-existing
ones so that a complete flux rope grows and ascends. When a macroscopic flux
rope is formed, we switch off the driving flows and find that the system
relaxes to a stable state containing a helical magnetic flux rope embedded in
an overlying arcade structure. A major part of the formed flux rope is threaded
by dipped field lines which can stably support prominence matter, while the
total mass of the flux rope is in the order of 4-5.e14 g.
