Geoff,
     I appreciate your interest in what has been one of the great challenge=
s of physics; i.e., to understand from first principles of theory the origi=
n and nature of our planet's magnetic field.  I don't know of any physicist=
, myself included, who has a satisfactory conceptual answer to questions yo=
u have posed.  The complexity of the matter, based in nonlinearity, makes i=
t a 'tough, near impossible, nut to crack'.  Greatly complicated numerical =
models, running on fast computers, apparently provide some insights; but to=
 my knowledge nobody has 'brought to the table' the kind of 'simplicity' th=
at physics always strives for.
     There is a 'model' of the Earth, having to do with earthquakes, that i=
s unrelated (at least directly) to its magnetic field; and which is very mu=
ch concerned with its crustal properties.   Your mention of an egg caused m=
e to think about this model once again.  Imagine our planet being somewhat =
similar to a multiply cracked hard-boiled egg.  The dynamics of the tidal f=
orce (moon/sun, mostly moon) acting on the crust as it rotates, can be thou=
ght of as like the cracked egg being rolled under pressure between the hand=
s.  Every snap, crackle, pop of the shell that happens because of this proc=
ess results in vibrations of the egg.  At a given time and position of a pa=
rticular rapid dislocation of shell parts, there is something like an earth=
quake; and thereafter there are dampened oscillations like free oscillation=
s (what physicists call eigenmodes).  Years ago (around 1990) my student na=
med M H Kwon saw with an instrument built for other purposes-free oscillati=
ons of the earth that were clearly correlated with the lunar cycle (and thu=
s the tidal force).   To my knowledge there has never been any interest sho=
wn in his PhD dissertation (or a paper that we wrote in 1995 on the matter)=
 by professionals of the seismology or geosciences world.  This has surpris=
ed me, since around 1998 there was something of a 'wood-stock of seismology=
' associated with the observation of near constant free oscillations of the=
 earth at higher (though still milli-Hertz) frequencies.
   Randall

Geoff,
     I appreciate your intere=
st in what has been one of the great challenges of physics; i.e., to unders=
tand from first principles of theory the origin and nature of our planet=
217;s magnetic field.  I don’t know of any physicist, myself inc=
luded, who has a satisfactory conceptual answer to questions you have posed=
..  The complexity of the matter, based in nonlinearity, makes it a =
216;tough, near impossible, nut to crack’.  Greatly complicated =
numerical models, running on fast computers, apparently provide some insigh=
ts; but to my knowledge nobody has ‘brought to the table’ the k=
ind of ‘simplicity’ that physics always strives for.  
     There is a &#=
8216;model’ of the Earth, having to do with earthquakes, that is unre=
lated (at least directly) to its magnetic field; and which is very much con=
cerned with its crustal properties.   Your mention of an egg caus=
ed me to think about this model once again.  Imagine our planet being =
somewhat similar to a multiply cracked hard-boiled egg.  The dynamics =
of the tidal force (moon/sun, mostly moon) acting on the crust as it rotate=
s, can be thought of as like the cracked egg being rolled under pressure be=
tween the hands.  Every snap, crackle, pop of the shell that happens b=
ecause of this process results in vibrations of the egg.  At a given t=
ime and position of a particular rapid dislocation of shell parts, there is=
 something like an earthquake; and thereafter there are dampened oscillatio=
ns like free oscillations (what physicists call eigenmodes).  Years ag=
o (around 1990) my student named M H Kwon saw with an instrument built for =
other purposes—free oscillations of the earth that were clearly corre=
lated with the lunar cycle (and thus the tidal force).   To my kn=
owledge there has never been any interest shown in his PhD dissertation (or=
 a paper that we wrote in 1995 on the matter) by professionals of the seism=
ology or geosciences world.  This has surprised me, since around 1998 =
there was something of a ‘wood-stock of seismology’ associated =
with the observation of near constant free oscillations of the earth at hig=
her (though still milli-Hertz) frequencies.  
   Randall
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