Near the Earth, the Solar Wind is diverted by the planet's magnetic field, forming a cavity in the solar wind. This cavity, the magnetosphere, is populated by plasma generated by cosmic rays and ultraviolet photons interacting with the atmosphere, and also some solar wind plasma which can penetrate the structure.

Injections of plasma from the tail of the magnetosphere manifest themselves in impressive auroral displays near the planet's poles, where the accelerated charged particles interact with the Earth's atmosphere.

Auroral displays are also produced in the polar regions by solar wind plasma entering the magnetosphere on the dayside, through the process of magnetic 'reconnection' or 'merging'. During the process, particles are energised sufficiently to power auroral emissions. These dayside and nightside processes are associated with the transport and circulation of magnetic flux within the magnetosphere.

Contained by the magnetic field of the Earth, within this magnetosphere, are the Van Allen radiation belts - regions of enhanced energy, increased density plasma populations which pose danger to satellites & human spaceflight.

Magnetospheres can also form round other magnetised bodies such as planets and some moons. These take different forms depending on the type of interaction. For more details see Comparative Magnetospheres

Francis Chen, Intro. to Plasma Physics, Plenum Pr., 1974 "A plasma is a quasineutral gas of charged and neutral particles which exhibits collective behavior"

T. Boyd and J. Sanderson, Plasma Dynamics, Barnes & Noble, 1969 "A plasma is any state of matter which contains enough free, charged particles for its dynamical behavior to be dominated by electromagnetic forces."

G. Parks, Physics of Space Plasmas, Addison-Wesley, 1991 "A plasma possesses properties that arise from both the individual interactions of the charged particles and those that come from the 'collective' behavior of particles. This behavior arises from many particles interacting simultaneously through the long-range Coulomb potential. The collective interactions are best described by the concepts of statistical physics."