I have also supplied a graphic explanation of the `Variable speed Core
` model at the following url

http://www.youtube.com/watch?v=CiCBrXKIH_0

....to accompany the model outlined below...



Studies of the seismic record indicate that seismic waves travel
fastest along a north-south axis from the southern hemisphere to
Siberia (and more recently suggesting an easterly shift to over
Alaska) implying that over the the last century it appears that the
earths solid core is rotating in an easterly direction. The conclusion
made from this data is that the earths solid inner core can be said to
be rotating west to east at approximately 1 degree longtitude a year
faster than the mantle.(Song, Richards 2005) This implies then, that
relative to Earths solid inner core, the mantle and the outer part of
the liquid core can be said to be moving in a westerly direction. This
also implies that there must be speed gradient in the liquid core
across its radius (relative to the mantle), of approximately 0 degrees/
year near the mantle to 0.1 degreeslongtitude/year near the solid
core. Thus using Lenzs` law, one can predict that the larger volume of
the outer part of the liquid core will induce a residual westerly
electrical current in the inner part of the liquid core (ie the outer
liquid core moves in a westerly direction relative to the inner part
of the liquid core). Flemings Right Hand rule predicts this westerly
direction of the electrical current will in turn induce a magnetic
south pole near Earths geographic North Pole. Recent experiments
confirm this, in that a freely rotating liquid metal will generate a
self sustaining magnetic field without a neccesary seed magnetic field
to kickstart the dynamo effect as previously thought.(Generation of a
Magnetic Field by Dynamo Action in a Turbulent Flow of Liquid Sodium.
R. Monchaux et al 2007).
As the seismic record shows that sound waves travel fastest across
earths N-S axis, this could also be consistent with the solid inner
core being slightly elongated in the earths N-S axis. (sound waves
travel fastest in a denser medium) Following from this, it can be
hypothesised that contrary to the speculation that the earths core is
a rigid crystal, one could alternatively give the `solid` inner core
non rigid, or elastic properties. Observations support this
possibility (Andrew Jephcoat and Keith Refson (2001-09-06). "Earth
science: Core beliefs". Nature 413: 27-30. doi:10.1038/35092650.) If
so its shape could then be said to oscillate over large timescales
between that of elongated in the N-S axis to stretched along the
equatorial plane. Obviously this implies that the inner cores`
rotational speeds would vary between slower and faster than the
mantle, when the solid core goes from wider at the equator to
stretched at the poles respectively. The historical record of Earths
pole reversals and changing field strength can thus be well modeled by
this variable core speed model. In that if currently it is accepted
that the `solid core` is stretched is the north south axis and rotates
faster than the mantle then it follows that when the cores volume
changes shape to that of more stretched in the equatorial axis, It
must then be forced to slow its rotational speed and therefore rotate
slower than the mantle . Not faster as currently observed. (ie the
core then will rotate in a westerly direction relative to the mantle)
In turn this would reverse the relative motion between the inner and
outer parts of the liquid core (as described above)
and in turn reverse the induced equatorial direction of the induced
electrical current which would then reverse the direction of earths
induced magnetic field from N-S to S-N. THis is observed in the
historical seismic record.
The current weakening of Earths magnetic field must then be due to the
solid cores` rotational speed slowing relative to the mantle. In other
words if it is assumed that currently the core is observed to be
travelling faster than the mantle in an easterly direction at 0.1
longitude per year than that rate must have been faster in the past
and will be slower in the future. This can only be explained if it is
assumed that the `solid` core itself is becoming less stretched in the
N-S axis and tending towards becoming stretched in the equatorial
axis.
To explain the observed off axis magnetic North pole using this
`variable core speed model` one can again refer to the seismic record
which shows that the axis of anisotropy, corresponding to the fastest
direction for seismic waves, tilts about 10 degrees from the Earth's N-
S axis of rotation, towards Siberia. From this data one can interpret
that the inner core not only could be `stretched` in the N-S axis but
also be physically tilted 10 degrees off axis towards Siberia as it
rotates within the earths core. In effect while it is rotating faster
than the mantle, its axis of mass is also tilted off center by 10
degrees and stretched slightly in the N-S axis. This will in turn
effect the equatorial rotation of the liquid inner core which acts as
a boundary between the mantle and the solid inner core. Modeling the
liquid core flow is always speculative for any model, but it is not
unreasonable to assume that a 10 degree off axis solid core that
rotates around its N-S center of mass could create a flow in the inner
part of the liquid core that was also tilted in an equal but opposite
10 degrees `off axis` in the equatorial plane. Resulting in an equal
and opposite tilt in the induced magnetic North pole of 10 degrees
towards the Arctic, using Lenz and Fleming as described previously.
This predicted tilt in the magnetic pole towards the arctic is
consistent with observation. As is the prediction that the axis of the
solid core is tilted towards Siberia.
The final element is to explain the northerly drift of the magnetic
North pole. There is insufficient seismic data to confirm or refute
this prediction but the variable core speed model presented in this
paper predicts that this would be due to an equal northerly drift of
the solid inner cores rotational axis from more than 10 degrees off
axis as currently observed to one that will be tilted by 0 degrees, or
directly N-S. In other words if the solid core is said to be currently
rotating tilted by 10 degrees off axis and this induces a off axis
electrical current and off axis magnetic pole. Then a solid core that
is aligned to earths geographic N-S axis as it rotates will generate
no off axis electrical current and therefore no off axis magnetic
field. In other words the cores volume is stretched in the N-S axis
and tilted by 10 degrees but is changing shape as it rotates so that
its N-S stretch is tending towards 0 degrees. In fact it would be more
correct to say that its nvolume is changing from stretched 10 degrees
off axis to not stretched in either the N-S or equatorial axis. This
would be in line with a slowing down of the solid cores rotational
speed as seen in the observed weakening of the overal magnetic field.
(The variable speed core model predicts that when the core is
perfectly circular in volume it rotational speed relative to the
mantle will be the same as the mantle ,ie 0 degrees per year. And *no*
magnetic field will be generated)
The conclusion this `variable speed core` model makes is that all the
combined observations of earths core and magnetic field indicate that
the solid core is currently stretched in the N-s axis, tilted off
center by 10 degrees and rotating faster than the mantle in an
easterly direction by 0.1 degrees per year. But also observations
indicate that it must be slowing down, relative to the mantle, tilting
its axis more towards earths vertical N-S geographical axis, and most
likely becoming less stretched in the N-S axis.

Sean
see this url for an accompanying graphic explanation of the variable
speed core model...
http://www.youtube.com/watch?v=CiCBrXKIH_0
www.gammarayburst.com