Due to the interaction of permanently incoming solar wind (coming from the left of the figure) with Earth's magnetosphere, a permanent collisionless shock called the bow shock (depicted by the yellow arc) is formed. The bow shock forms in front of the nose of the magnetopause – the external boundary layer of the magnetosphere.

Credits: ESA

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.