Satgen 499  Magnetism Pt6  by GM4IHJ   (BID SGEN499)   1998-10-17

The "REMANENT" magnetism of volcanic material mentioned in Satgen498,
is a good guide to the direction and strength of the earth's magnetic
field when the volcanoes were active, and their magnetic lava cooled
through its "Curie" point temperature and fixed its magnetic field.
Inspection of old volcanoes around the world has given us a good
picture of magnetic activity , through several field reversals
stretching back about 60 million years . But before that time there
seems to have been a period of constant unvarying magnetic polarity
going back for many millions of years. So while modern science can
tell us quite a lot about earth magnetism, the major features of
reversals and their spasmodic timing are definitely not yet
understood. Nor do we even know why, during periods of fixed polarity
, the actual location of the magnetic dip poles wanders around the
Arctic and Antarctic, in cycles taking hundreds of years.

Big changes such as reversals of polarity , seem to signal their
coming by a very slow many thousand year decline in field strength.
But once the decline flips into reversal the climb back up to normal
field strength in the new direction is very fast, remaining at peak
for several thousand years before starting the slow decline to a new
reversal.

Considered over long term ( millions of years ) , the earths magnetic
field is presently at an unusually high level. So we are unlikely to
see much change in our life times except slow dip pole drift. Several
authors have pointed out that the earths magnetic field protects us
from the relatively high radiation flux (circa 50rad/year) from space.
But they then go on to suggests protecting space ships beyond the
earth in a similar magnetic field. This is a mistake , noting that it
is the earths atmosphere which is our best protection. Magnetic field
protection for astronauts would need to be much stronger in field
strength than the earths field, and we do not know if the high levels
of field strength required would be deleterious to human beings - a
case of the cure , possibly being worse than the disease.

PS  DRACONIDS/GIACOBINIDS METEOR SHOWER.  Have had lots of mail and
reports about this "Non Event". At IHJ there was a strong event but
not at the time forecast for good evening viewing.
8th Oct 0600z moderate enhancement of usual morning random meteors
        0950z Meteor shower had started almost continuous small pings
        1223z Continuous mix of big and small pings  until about 1600z
        1612z Shower activity decreasing fast
        1730z activity almost ceased

Observations were made by radio using a group of European TV video
carriers around 48.250 MHz as the signal sources, with meteor trail
reflections being received via a 6m antenna feeding a Drake R8E
receiver. Audio from the receiver being fed to a computer sound card
and AF9Ys FFTDSP software.