This image shows a three-dimensional cut-away view of the magnetic 'bubble' surrounding Earth, called magnetosphere. The curly features sketched on the boundary layer are the so-called 'Kelvin-Helmholtz' vortices discovered by Cluster [Hasegawa et al., 2004].

The vortices, or whirlpools, originate where two adjacent flows of electrically charged gas (plasma) travel with different speed. In this case, one of the flows is the heated gas inside the boundary layer of the magnetosphere, the other one is the solar wind just outside it. The white dashed arrow shows the trajectory followed by Cluster when the vortices where discovered.