Origin of Mercury's double magnetopause: 3D hybrid simulation study with A.I.K.E.F.

► We succeeded to model Mercury's double-magnetopause. ► Results are in excellent agreement with plasma observation made by the MESSENGER-spacecraft. ► The double-magnetopause may even exist in the absence of planetary ions. ► The inner current layer turns out to be a diamagnetic current system. ► This current is sustained by protons that are mirrored between north and south pole.