THE EARTH'S MAGNETOSPHERE

The magnetosphere is the Earth's magnetic environment. The Earth is a huge dipole (2-pole) magnet. The Earth's magnetic field is probably cause by its molten iron-nickel core. This magnetic field is aligned with the north and south poles, and has reversed many times during geologic history.

The Earth's magnetic field is about 0.32 Gauss at the equator and about 0.62 Gauss at the poles.

William Gilbert hypothesized that the Earth was a giant magnet in 1600. Thomas Gold proposed the name "magnetosphere" in 1959. The Earth's magnetosphere extends far into space and is influenced by the solar wind (ions and electrons emitted from the sun). It extends into space from 60 to 37,280 miles (100 to 60,000 km) towards the Sun, and over 186,500 miles (300,000 km) away from the Sun (nightward), forming the Earth's magnetotail.

The magnetopause is the boundary between the area in which the Earth's magnetic field dominates and the magnetic field of the rest of the Solar System dominates.
 

Auroras:
Charged particles become trapped on the field lines of the magnetosphere. Auroras appear when trapped particles from the solar wind spiral towards a pole. These beautiful arcs of lights in the near-polar sky are caused by gases that become excited after being hit by solar particles. Most auroras are 100 to 250 km above the ground (in the ionosphere).