  There is a heated debate regarding the specific roles played by ideal
magnetohydrodynamic (MHD) instability and magnetic reconnection in the causes
of solar eruptions. In the context with a pre-existing magnetic flux rope (MFR)
before an eruption, it is widely believed that an ideal MHD instability, in
particular, the torus instability, is responsible for triggering and driving
the eruption, while reconnection, as invoked in the wake of the erupting MFR,
plays a secondary role. Here we present a new numerical MHD model in which the
eruption of a pre-existing MFR is primarily triggered and driven by
reconnection. In this model, a stable MFR embedded in a strapping field is set
as the initial condition. A surface converging flow is then applied at the
lower boundary, pushing magnetic flux towards to the main polarity inversion
line. It drives a quasi-static evolution of the system, during which a current
layer is built up below the MFR with decreasing thickness. Once reconnection
starts in the current sheet, the eruption commences, which indicates that the
reconnection plays a determining role in triggers the eruption. By further
analyzing the works done by in the magnetic flux of the pre-existing MFR and
the newly reconnected flux during the acceleration stage of the eruption, we
find that the latter plays a major role in driving the eruption. Such a model
may explain observed eruptions in which the pre-eruption MFR has not reached
the conditions for ideal instability.
