Re: south in the north

[David Bowman <dbowman@tiger.georgetowncollege.edu>]

Ludwik asks:
> I have another question about magnetic poles. Suppose that the location
> of N and S are exactly located on Earth. For example, by mapping the dip
> angles, averaging from satellites, etc. Are we absolutely sure that the
> the N-S line passes the center of mass of our planet?

I don't know about you, but I am not "absolutely sure that the N-S line"
even exists as a well-defined locus.  I suspect that it does not.  Just
consider how complicated the field pattern must be in the outer core as
it is entangled with the complicated convective cells and flow fields
of the fluid and electric currents.  This is a highly nontrivial MHD
problem.  In any event, whatever the field happens to be there is no
reason to assume that it is centered on the center of mass of the Earth.
I believe it is common for planets with magnetic fields to have the
location of their magnetic dipole moment shifted significantly off of
the planet's center of mass, and indeed, even off of the planet's spin
axis, and the orientation of that moment is seldom quite well-aligned
with the spin axis as well.

David Bowman
dbowman@georgetowncollege.edu
note new^^^^^^^^^^^^^^^^^^^^^domain name