Download The mysteries of the Earth`s magnetic field and sunspots

The mysteries of the Earth’s
magnetic field and sunspots
by Professor Annraoi de Paor
(National University of Ireland, Dublin)
at the IEE, Savoy Place, London WC2R 0BL
on Thursday, 7 March 2002 at 6 pm (tea at 5.30 pm).
Synopsis
The directional property of the magnetic compass has been known since antiquity, but was thought to be caused by the
stars until William Gilbert (1540-1603), in his great treatise “De Magnete....”, published in London in 1600 showed
conclusively that the Earth is a magnet. In 1820, André Marie Ampère (1775-1836) proposed that all magnetism is due
to electricity in motion. He considered that orthogonal currents are necessary to produce the Earth’s field—circular for the
main field and North-South for time-varying declination. He thought that these currents flow through the atmosphere. In
1867, William Thomson, later Lord Kelvin (1824-1907), proved that magnetic phenomena at the Earth’s surface and
above it could be reproduced by an internal distribution of electric current. The current view as to how these could arise
originated with Joseph Larmor (1857-1942), who suggested in 1919 that self-excited dynamo action in swirling fluids in
the Earth’s core is responsible. Larmor initiated Geodynamo Theory, which has been extensively cultivated in attempts to
develop a self-consistent theory.
About the Speaker
Professor Annraoi de Paor stumbled into this field in mid-1998, solving a mathematical problem posted on the Internet
by Raymond Hide, Emeritus Professor of Geophysics at Oxford, ostensibly to do with proving absence of chaos in the
dynamics of a particular self-excited dynamo driving a series-wound motor. On meeting Professor Hide and learning the
true origin of the problem, in Geodynamo Theory, he was intrigued enough to embark on the search for the elusive selfconsistent theory. In the midst of a bout of ‘flu, at 3:20 am on the morning of 19 February, 1999, he was granted an
overwhelmingly clear, technicolour, animated vision of electromagnetic processes in the Earth’s core, which apparently
resolved the problem. Ampère’s orthogonal currents recur naturally (but within the Earth), coupled by the Hall Effect
(discovered by Edwin Hall (1855-1938) in 1879), newly interpreted here as an orthogonal axis energy transfer
mechanism. One of these currents, postulated to be also flowing in sheets beneath the surface of the Sun, explains the
11-year optical, 22-year magnetic, cycling of Sunspots, with opposite magnetic polarities in Northern and Southern
hemispheres.
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