Earth's Magnetic Field

Internet resources

NASA Goddard Space Flight Center's The Exploration of the Earth's Magnetosphere especially sections #2 and #5

Space Weather Center webpage on Giant Magnet Earth

NOAA's National Geophysical Data Center's FAQ page (highly recommended)

The U.S. Geological Survey's National Geomagnetism Program

How to construct a simple soda bottle magnetometer

Try your hand at magneto minigolf or magneto bowling


Historical outline

6th c. BCThales of Miletus writes about properties of magnetism
c. 1000 ADNavigational compass invented in China
1187earliest record of compass in Europe
1510Georg Hartman recognizes difference between magnetic and geographic north (known as declination)
1576Robert Norman notes inclination (deviation from horizontal) of magnetic field
1600William Gilbert suggests Earth is a giant bar magnet
1635Henry Gallibrand discovers that magnetic north pole slowly wanders
1716Russian sailors see wild compass fluctuations during auroral displays
1724George Graham; Anders Celsius notice compass needle fluctuations
1806Alexander von Humboldt observes compass fluctuations coincident with auroral display
1820Hans Christian Oersted finds that electric currents deflect compass needle
1825André-Marie Ampère formulates law for magnetic force between currents
1830'sHumboldt establishes world-wide measuring network, finds simultaneous global fluctuations, coins phrase "magnetic storm"
1846Michael Faraday introduces concept of "lines of force"
1852Edward Sabine notes 11-year cycle of magnetic storm frequency
1864James Clerk Maxwell formulates theory of electromagnetism
1882Balfour Stewart suggests upper atmospheric currents as source of magnetic fluctuations
1904E. W. Maunder notes 27-day recurrent magnetic storms
1906Richard Oldham establishes existence of Earth's core
1929Motonori Matsuyama shows Earth's magnetic field reverses polarity every few hundred thousand years


The Van Allen Belts

a.k.a. The Radiation Belts

Internet resources

Windows to the Universe Radiation Belt page

NASA GSFC's The Exploration of the Earth's Magnetosphere Section #12
Sections #9 through #11 provide more background

Website for the twin Radiation Belt Storm Probes launched on Aug 30, 2012
RBSP movie trailer


Historical outline

1896Henri Becquerel discovers radioactivity
1898Ernest Rutherford reports existence of alpha- and beta-rays
1903Becquerel awarded Nobel Prize along with Pierre and Marie Curie
1907Carl Störmer describes theory of magnetically trapped particles
1908Rutherford awarded Nobel Prize
1912Victor Hess discovers cosmic rays
1913Hans Geiger invents Geiger counter
1936Hess awarded Nobel Prize
1956S. Fred Singer proposes existence of trapped charged particles around the Earth
Oct 4, 1957Russians launch Sputnik I
1958James van Allen discovers (inner) radiation belt with Geiger counter aboard Explorer I satellite
1958Singer; Paul Kellogg, S.N.Vernov propose radiation belt created by cosmic rays
1958Project Argus nuclear explosion
1958Pioneer 3 discovers outer radiation belt
1962Nuclear explosions in the inner belt (Starfish - U.S.) and the outer belt (Russian)
1963Upper atmospheric nuclear tests banned by international treaty
1973Anomalous Cosmic Rays (ACR) discovered by Pioneer 10
1985-88COSMOS satellites suggest existence of trapped ACR (interstellar particles)
1992SAMPEX satellite confirms belt of high energy interstellar particles