  This study aims at investigating the ability of strong interactions between
magnetic field concentrations during their rise through the convection zone to
produce complex active regions at the solar surface. To do so, we perform
numerical simulations of buoyant magnetic structures evolving and interacting
in a model solar convection zone. We first produce a 3D model of rotating
convection and then introduce idealized magnetic structures close to the bottom
of the computational domain. These structures possess a certain degree of field
line twist and they are made buoyant on a particular extension in longitude.
The resulting twisted $\Omega$-loops will thus evolve inside a spherical
convective shell possessing large-scale mean flows. We present results on the
interaction between two such loops with various initial parameters (mainly
buoyancy and twist) and on the complexity of the emerging magnetic field. In
agreement with analytical predictions, we find that if the loops are introduced
with opposite handedness and same axial field direction or same handedness but
opposite axial field, they bounce against each other. The emerging region is
then constituted of two separated bipolar structures. On the contrary, if the
loops are introduced with the same direction of axial and peripheral magnetic
fields and if sufficiently close, they merge while rising. This more
interesting case produces complex magnetic structures, with a high degree of
non-neutralized currents, especially when the convective motions act
significantly on the magnetic field. This indicates that those interactions
could be good candidates to produce eruptive events like flares or CMEs.
