Solar Wind:

The charged particles from the Sun, continually streaming outward via the solar system, deform the geomagnetic field. This solar wind in effect "blows" the field out of shape. On the side of Earth facing the Sun, the field is compressed; on the side of the Earth opposite the Sun, the field is extended out. This effect takes place with the magnetic fields about the other planets, also notably Jupiter.

As Earth rotates, the geomagnetic field does a complicated twist-and-turn dance into space in the direction facing away from the Sun. At near the Earth's surface, the field is almost symmetrical with respect to the geomagnetic poles. Since the distance from the Earth rises, the extent of geomagnetic-field distortion also increases.