Variation of the dipole strength in super and sub-Alfvénic regime: Dione-type to Ganymed-type interactions (Invited)

We focus on identifying transition mechanisms between interactions close to Jupiter's and Saturn's moons using the hybrid model simulation code AIKEF. Our study started with the transition from a lunar type obstacle in super-Alfvénic regime (Moon-type interaction) to a sub-Alfvénic regime (Dione-type interaction). This showed systematic Alfvén wings and fast mode structures which angle is a function of the upstream velocity. We carry on similar studies with implementing a magnetic dipole and a core. At first, for sub-Alfvénic interactions close to the Ganymede type, increasing the dipole momentum leads to reconnection processes. This triggers flow acceleration at the poles and generates currents feeding the Alfvén wings. Increasing the upstream velocity to a super-fast magnetosonic velocity leads to the generation of a bow shock, magnetopause and a night side cavity as well as several current loops in the wake between the equatorial plane and the magnetospheric boundary. The numerous configurations are split and summed up in a three dimensional representation, through several qualitative steps using currents identification. Example of interaction for an obstacle with twenty inertial lengths radius and surface magnetic field equal to ten times the IMF. The magnetic moment is anti-parallel to the IMF. Upstream velocity is one Alfvén Mach.