I read on several internet sites recently that the Earth’s magnet field has weakened over the last 150 years that it has been measured. Could this have something to do with the non-polarized collection of ferrite materials in big cities or due to electro-magnetic radiation from electrical machines?
Has anyone studied Magnetic field variations around large cities?
RR in NC
The dipole field has reversed directions numerous times over the course of the history of the earth. The dipole field is the component of the field that has one north and one south pole. There are other, higher order field components that have two north and two south poles, three north and three south, etc. Right now the dipole is the dominant field but that could be changing if the direction of that field is in the process of reversing.
According to Prof. Stephen C. Brush of the University of Marhland in the book Scientists Confront Creationism as the dipole field has weakened the higher order fields have strengthened and the total field strength has remained about the same.
The reversal seems to be a natural result of instabilities in the circulation of liquid material in the outer core of the earth and has nothing to do with the activities of people as far as we can tell with current knowledge.
That should have been “Maryland,” of course.
If the magnetic field does vanish (temporarily during a reversal) then we could be in trouble as the fields screens the earth from lots of nasty cosmic rays.
Many scientist think we are now due for a reversal soon as these seem to happen very regularly. But don’t worry, it probably won’t happen for another 10,000 years or so, and will take thousands of years to happen when it does.
I’m a long way from an expert in this, or much of anything else – and now the “but” — from all I’ve read the energy in the magnetic field of the earth arises out of the energy of circulation of the earth’s liquid outer core. That circulation pattern can take different forms and for short periods might even be chaotic, but the total energy and the total amount of circulation stays relatively constant. So the total magnetic field energy probably also stays relatively constant. The lack of a dominant two-pole field might change the way incoming, charged particles from the solar wind and primary cosmic rays are distributed over the surface, but might not change to total of incoming particles that strike the surface.
Several reversals of the dipole field have occurred while life has existed on the earth. Does anyone have a cite that correlates large changes in life on the earth with such reversals? I have looked and can’t find one.
David you seem to be right
http://www.newton.dep.anl.gov/askasci/env99/env034.htm
“The magnetic field does not protect the earth from solar flares. It simply guides the ions of the solar wind to the polar regions, where their energetic collisions with the upper atmosphere produce the luminous plasma known as the Northern and Southern Lights (Aurora Borealis and Aurora Australis). It is the earth’s atmosphere that actually prevents the solar wind from reaching the surface, and that is independent of the magnetic
field.”
However all those animals and birds that use the magnetic fields for navigation are in for a shock!