  In a nanopillar with dipolarly coupled vortices, we present an experimental
and simulation study to understand how the interplay between the bias field and
spin transfer torque impacts reversal of the vortex cores. We find that,
depending on the current values, vortex cores might experience different
physical mechanisms for their reversal, namely a static or a dynamic switching.
We believe that our results might be useful in the context of vortex based non
volatile memories, as a current controlled selective core switching is
proposed.
