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Re: Earth's Magnetic Field



Dear Mr.. Yeend,

    My geophysics might be a bit rusty but I believe that seismographic S waves reflect a pattern consistent with an Earth core composed of a liquid outer core surrounding a solid inner core.  The core is believed to be comprised mostly of Fe and Ni.   The Earth's magnetic field is generated as the outer liquid core with charged ions (i.e., electrical current) moves around solid inner core.

    There have been scholarly observations of  the earth's magnetic field for almost 500 years.

     Sir William Gilbert published the first treatise on the earth's magnetic field ( De magnete).  Gilbert showed that the reason compass needles point toward the earth's north pole is because the earth itself appears to behave as a large magnet.  Gilbert argued that the earth's magnetic field is roughly equivalent to that which would be generated by a bar magnet located at the center of the earth and oriented along the earth's rotation axis.

    Later in the mid-nineteenth century, Karl Frederick Gauss confirmed Gilbert's observations and also showed that the magnetic field observed on the surface of the earth could not be caused by magnetic sources external to the earth, but rather had to be caused by sources within the earth.

    I hope this gives you a good start.

Best Regards,
K. Lee Lerner
Fellow, Emeritus, Science Policy Institute
Physics and Chemistry Teacher