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From: flinn@seismo.UUCP (E. A. Flinn)
Newsgroups: net.physics
Subject: Re: Reversing of Magnetic Poles
Message-ID: <1458@seismo.UUCP>
Date: Sun, 3-Jun-84 09:40:38 EDT
Article-I.D.: seismo.1458
Posted: Sun Jun  3 09:40:38 1984
Date-Received: Tue, 5-Jun-84 19:30:44 EDT
Distribution: net
Organization: Center for Seismic Studies, Arlington, VA
Lines: 30

|>>I have heard rumor that in the year 2000 (+ or - a few years)
|>>the magnetic poles of the earth are going to do a flip-flop.
|>>Is this only a rumor or is there some truth to it?  

	No and yes.  The strength of the geomagnetic field has been
decreasing almost linearly for many years.  The measurements made by
Magsat in 1979 confirmed that *if* this linear decrease continues, the
field strength will vanish in about 1100 years from now.  Other
changes are also taking place - the non-dipole components of the field
are changing, there is the well-known westward drift of the
geomagnetic field, and the inclination of the dipole component is
gradually changing.

|>>If it is true, is it going to be a gradual change of polarity or rapid? 

	Gradual, if the linear trend continues.  The field has
reversed direction many times in geological history, so presumable the
field will keep on changing, the north and south poles having changed
identity.

|>>What impact might it have on our magnetic shielding from
|>>solar radiation?  

	There is no evidence for species extinctions at the previous
times of magnetic reversals, so it seems unlikely that life on earth
would be profoundly affected.  We will be bombarded by the solar wind
for a few hundred years, and I haven't seen any discussions of the
environmental implications of this sort of thing.

	-- Ted Flinn