The Moon is well outside the normal reach of the Earth's magnetic field. There is a 'tail' extending away from the sun, because of the solar wind, which the Moon might enter at certain times when it is on the far side of the earth from the sun, but normally it is well outside the field.
http://en.wikipedia.org/wiki/Magnetosphere
On the sun's side of Earth, the magnetopause distance is approximately 10 Earth-radii. Abreast of the earth the distance grows to about 15 earth radii (distances change with solar wind pressure and density; The magnetosphere is made to flap and compress by the solar wind) while on the night side it extends into a long cylindrical magnetotail at least several hundred radii long, gradually turning into a wake.
Since the earth's radius is about 4,000 miles that makes the magnetosphere about 40,000 miles on the sun side and about 60,000 on the trailing/leading sides. The outward side is obviously highly variable but the Moon doesn't orbit exactly on the earth's equatorial plane so it won't necessarily contact this tail even when out the outward side of its orbit.
http://www.enchantedlearning.com/sub...tosphere.shtml
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 Moon orbits just about 220,000 to 250,000 miles from earth so it would only rarely enter this 'tail' when it was at its most extended.
[ March 27, 2004, 21:15: Message edited by: Baron Munchausen ]