A Millennium of Geomagnetism
Reviews of Geophysics, 40(3), p.1-1 to 1-30, Sept 2002
David P. Stern, Laboratory for Extraterrestrial Physics
Goddard Space Flight Center, Greenbelt, MD 20771|
Appendix: A Chronology of Geomagnetism
Best read in 12-point "Times" font
- 1000 (approx) Chinese discover that lodestone floating on
"boat" prefers south-north direction.
- 1187 Alexander Neckham describes pivoted compass.
- 1269 Letter by Petrus Peregerinus describes properties of
- 1492 Columbus sails for America, notes declination changes
in mid-ocean from easterly to westerly.
- 1581 Robert Norman publishes "The Newe Attractive,"
announcing the discovery of magnetic dip (inclination).
- 1600 William Gilbert's "De Magnete": Earth itself is
a great magnet.
- 1634 Henry Gellibrand discovers the secular variation of declination.
- 1699 Edmond Halley conducts the first magnetic survey.
- 1722 George Graham discovers diurnal variation of declination.
- 1741 Graham in London and Celsius in Sweden observe
simultaneous magnetic perturbations due to the polar aurora.
- 1777 Coulomb introduces his torsion balance, later shows magnetic
forces (electric ones, too) obey an inverse squares law.
- 1801 Alessandro Volta demonstrates his "voltaic pile," the first battery.
- 1820 Oersted discovers magnetism due to electric currents.
- 1820 Ampere explains magnetism in terms of
forces between electric currents.
- 1828 Von Humboldt urges Gauss to study magnetism. Later Gauss develops
method to measure magnetic intensity and an electrical telegraph.
- 1831 Faraday discovers electrical induction, later introduces disk dynamo.
The Rosses and Sabine reach the northern magnetic pole.
- 1832 Faraday tries to detect a dynamo current in water flowing in the Earth's field.
- 1834 Gauss founds "Göttingen Magnetic Union," later (1836-9) develops
spherical harmonic analysis of the scalar magnetic potential.
- 1843 Heinrich Schwabe publishes first evidence for the sunspot cycle.
- 1851 Von Humboldt publishes Schwabe's work; sunspot cycle widely accepted.
- 1852 Sabine finds evidence that magnetic storms follow the sunspot cycle.
- 1859 Richard Carrington observes white-light solar flare, followed by large
- 1892 George Ellery Hale introduces spectroheliograph.
- 1895 Kristian Birkeland begins experimenting with electron beams and
terrellas. Henri Poincare calculates a simple motion of trapped particles.
- 1896 Pieter Zeeman discovers splitting of spectral lines emitted in magnetic field.
- 1903 Birkeland proposes the existence of "polar magnetic storms," He also
suggests aurora is caused by electron beams emitted from the sun.
- 1906 Bernard Brunhes publishes first evidence of reversely magnetized
- 1908 Hale uses the "Zeeman effect" to show sunspots are intensely magnetic.
- 1909 Douglas Mawson reaches the southern magnetic pole, at the edge
- 1912 Arthur Schuster proposes magnetic storms are evidence for a
"ring current" in space, circling the Earth.
- 1918 Alfred Wegener publishes "The Origin of the Continents and Oceans."
- 1919 Joseph Larmor proposes that magnetic fields of sunspots
may be produced by a self-sustaining dynamo action.
- 1929 Motonori Matuyama produces evidence that reversely magnetized
rocks may have originated when the Earth's magnetic polarity had reversed.
- 1930 Chapman and Ferraro suggest magnetic storms are due to plasma clouds
from the sun (not electron beams), enveloping the Earth's magnetic field.
- 1930 Alfred Wegener dies in the snows of Greenland.
- 1933 Thomas Cowling proves self-sustained dynamos are never axisymmetric.
- 1946 Walter Elsasser tries to calculate dynamo solutions.
- 1947 Giovanelli: magnetic neutral points near sunspots are site of flare
- 1951 Jan Hospers publishes study of Icelandic lavas, concludes from their
magnetization that reversals were real.
- 1952 Runcorn promotes "polar wandering" to explain magnetic
- 1955 Franklin and Burke detect radio emissions from Jupiter.
Eugene Parker proposes way for solar toroidal fields to
strengthen the poloidal field.
- 1957 Sputnik 1 and 2 begin the era of spaceflight. Fred Singer proposes
a ring current carried by trapped low-energy particles.
- 1958 Explorers 1 and 3 discover the inner radiation belt. Eugene Parker
predicts the solar wind.
- 1959 Tom Gold coins word "Magnetosphere."
Drake proposes Jupiter has a radiation belt.
- 1961 Hess and Dietz propose Earth's crust spreads out from mid-ocean ridges.
Magnetic reconnection and plasma convection in the magnetosphere
proposed by Dungey, Axford and Hines.
Babcock proposes empirical theory of sunspot cycle.
- 1963 Morley, Vine and Matthews propose that magnetic banding of the ocean
floor is produced by seafloor spreading and polar reversals.
Magnetopause crossed by Explorer 12.
Mariner 2 maps solar wind and its streams.
- 1963 IMP 1 launched, first mapping of the Earth's magnetotail.
Vanguard 3 maps the Earth's internal field from orbit.
- 1964 Akasofu, Meng et al. analyze morphology of magnetic substorms.
Braginsky. publishes solutions to the kinematic dynamo problem.
- 1965 Heirtzler produces map of symmetric magnetic banding of the ocean floor.
- 1966 Steenbeck at al propose "alpha dynamo," generalizing an idea of Parker.
- 1969 Schields, Dessler and Freeman propose a system of "Birkeland currents"
linking Earth to space.
- 1971-72 Lunar magnetic field surveyed by lunar satellites from Apollo 15, 16.
- 1972 OGO 7 observes "coronal holes", later studied aboard "Skylab."
- 1973 Zmuda and Armstrong publish map of polar "Birkeland currents."
- 1973 Pioneer 10 crosses Jupiter magnetosphere (4 December), followed
by Pioneer 11 (1974), Voyagers 1 and 2 (1979) and Galileo (enters orbit, 1995).
- 1974 Mariner 10 flies by Mercury, observes its magnetic field.
- 1975 Lowes and Wilkinson demonstrate dynamo action in the lab.
- 1979 Voyager 1 passes near currents induced by Io's motion relative to Jupiter.
- 1979 Pioneer 11 passes magnetosphere of Saturn, followed by
Voyager 1 (1980) and Voyager 2 (1981)
- 1981 First precision mapping of the Earth's field from space, by Magsat.
- 1986 Voyager 2 passes magnetosphere of Uranus.
- 1989 Voyager 2 passes magnetosphere of Neptune.
- 1994 Ulysses observes fast solar wind above Sun's south pole.
- 1997 Mars Global Surveyor observes Mars crustal magnetization, no core field.
Mapping phase, March '99--Aug 2000.
- 1997 Glatzmaier et al. use computer to simulate the Earth's dynamo and its reversals.
- 1999 "Oersted" satellite launched to map the Earth's main field.
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Author and Curator: Dr. David P. Stern
Mail to Dr.Stern: earthmag("at" symbol)phy6.org
Last updated 25 November 2001