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

Table of Contents Clicking on any marked section on the list below brings up a file containing it and all unmarked sections immediately following it on the list. This list is repeated at the beginning of each file. Introduction Early discoveries William Gilbert Halley Coulomb Oersted and Ampere The Lodestone Gauss and Humboldt Explorations and Surveys Faraday's Lines of Force (field lines) Faraday's Disk Dynamo Sunspots The Dynamo Process on the Sun The Earth's Dynamo Dipole Reversals and Plate Tectonics Magnetic Storms and Ring Currents The Magnetosphere Magnetic Reconnection Planetary Magnetospheres Assessment Chronology of Geomagnetism References: A-G References: H-P References: Q-Z Back to the index page

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
                    magnets.
• 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
                    magnetic storm.
• 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
                    rocks.
• 1908       Hale uses the "Zeeman effect" to show sunspots are intensely magnetic.
• 1909       Douglas Mawson reaches the southern magnetic pole, at the edge
                    of Antarctica.
• 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
                    energy release.
• 1951       Jan Hospers publishes study of Icelandic lavas, concludes from their
                    magnetization that reversals were real.
• 1952       Runcorn promotes "polar wandering" to explain magnetic
                    reversals.
• 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