The solar wind is a continuous flow of particles from the Sun consisting of electrically charged particles in a state known as plasma. The Earth’s magnetic field is distorted by the solar wind to a droplet-shaped magnetic bubble called the magnetosphere. On the nightside, the Earth’s magnetic field is stretched into a long tail, the magnetotail, much like the tail of a comet.
The blue cavity represents the magnetosphere. The red area denotes the region where a large amount of charged particles reside and intense electric currents flow within the magnetosphere. The four Cluster satellites encountered a flow reversal region in the magnetotail.