The magnetosphere is the region of space in which a planet's magnetic field dominates that of
the solar wind. It is distorted into a
teardrop shape by the solar wind pushing on the dayside and drawing out
a long magnetotail on the nightside. Earth's
magnetosphere normally extends about 10 Earth radii on the dayside, while
its tail stretches out several hundred Earth radii in the anti-sunward direction.
It is, however, a highly dynamic structure that responds dramatically to
changes in the dynamic pressure of the solar wind and the orientation of
the interplanetary magnetic field. Its ultimate
source of energy is the interaction with the solar wind. Some of the energy
extracted from this interaction goes directly into driving various magnetospheric
processes, while some is stored in the magnetotail, to be released later
Significant magnetospheres also exist around Mercury and the four gas giants of the Solar System – Jupiter, Saturn, Uranus,
and Neptune. The Sun's own, enormous magnetosphere
is called the heliosphere.
PHENOMENA AND STRUCTURES