3D illustration of the proposed mechanism to explain the Io footprint leading and secondary spots. The plasma torus, formed by ionized particles coming from Io’s volcanism. The current system formed by the plasma waves generated by the motion of Io in the plasma torus stream is represented in blue. It is the root cause for the main spot in each hemisphere. The electron beams are shown in red. They are expected to be the cause for the leadings spot (in the North) and for the secondary spot (in the South). Credit: LPAP/Université de Liège
