April 16, 2001
Q: What is the Earth's magnetic field?
A: The Earth acts like a great spherical magnet, in that
it is surrounded
by a magnetic field. The Earth's magnetic field resembles, in general, the
field generated by a dipole magnet (i.e., a straight magnet with a north
and south pole) located at the center of the Earth. The axis of the dipole
is offset from the
axis of the Earth's rotation by approximately 11
degrees. This means that the north and south geographic poles and
the north and south magnetic poles are not located in the same
place.
At any point, the Earth's magnetic field is characterized
by a direction and intensity which can be measured. Often the
parameters measured are the magnetic declination, D, the horizontal
intensity, H, and the vertical intensity, Z. From these elements,
all other parameters of the magnetic field can be calculated.
