This artist’s impression shows the Earth’s magnetosphere surrounded by solar wind constantly flowing out of the Sun (coming from the left side of the figure). The white rectangle on the left identifies the area where ESA’s Cluster and China/ESA Double Star’s satellites discovered density holes in March 2005.

The sketch on the left illustrates these observations: the brown dots represent the solar wind and ions back-streaming against the solar wind flow, along the interplanetary magnetic field lines (in black). The elongated ellipses along the magnetic field lines represent the new type of density holes – constantly growing and popping bubbles of superheated gas – discovered in the plasma (gas of charged particles) surrounding Earth. Within these bubbles the strength of the magnetic field is reduced to almost zero, as illustrated by the thinner black lines within the holes.