Magnetosphere chronology

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[edit] Chronology

1600 William Gilbert in London suggests the Earth is a giant magnet.

1741 Hiorter and Anders Celsius note that the polar aurora is accompanied by a disturbance of the magnetic needle.

1820 Hans Christian Oersted discovers electric currents create magnetic effects. André-Marie Ampère deduces that magnetism is basically the force between electric currents.

1843 Samuel Schwabe, a German amateur astronomer, shows the existence of an 11-year sunspot cycle.

1859 Richard Carrington in England observes a solar flare; 17 hours later a large magnetic storm begins.

1892 George Ellery Hale introduces the spectroheliograph, observing the Sun in hydrogen light from the chromosphere, a sensitive way of detecting flares. He confirms the connection between flares and magnetic storms.

1900-3 Kristian Birkeland experiments with beams of electrons aimed at a magnetized sphere ("terrella") in a vacuum chamber. The electrons hit near the magnetic poles, leading him to propose that the polar aurora is created by electron beams from the Sun.

- Birkeland also observes magnetic disturbances associated with the aurora, suggesting to him that localized "polar magnetic storms" exist in the auroral zone.

1902 Marconi successfully sends radio signals across the Atlantic Ocean. Oliver Heaviside suggests that the radio waves found their way around the curving Earth because they were reflected from electrically conducting layer at the top of the atmosphere.

1926 Gregory Breit and Merle Tuve measure the distance to the conducting layer--which R. Watson-Watt proposes naming "ionosphere"--by measuring the time needed for a radio signal to bounce back.

1930-1 After Birkeland's "electron beam" theory is disproved, Sydney Chapman and Vincent Ferraro in England propose that magnetic storms are caused when plasma clouds ejected from the Sun envelope the Earth.

1949 A sudden increase in cosmic rays is traced to an eruption on the Sun. A much larger "flare event" occurs on February 23, 1956.

1953 Owen Storey proves that "whistler" radio waves are produced by lightning and are often guided through distant space along field lines of the Earth's magnetic field.

1954 Meredith, Gottlieb and Van Allen use a rocket in the auroral zone to detect radiation from the aurora. [1]

1957 Sputnik 1 launched by the Soviet Union, the first artificial satellite.

1958 Explorer 1, built by Van Allen and his Iowa group and launched by the US January 31, observes the radiation belt. Explorer 3, launched in March, comes up with the first clear evidence for its existence.

- Eugene Parker (Chicago) proposes the theory of the solar wind.

- Pioneer 3 observes the outer radiation belt.

- "Project Argus," 3 small nuclear bombs above the south Atlantic Ocean, creates (3 times) artificial radiation belts, lasting about 2 weeks. The project also creates artificial aurora.

1959 Thomas Gold proposes the name "Magnetosphere"

1961 James Dungey in Britain proposes a reconnection mechanism for transmitting solar wind energy to the magnetosphere by direct magnetic linkage between the two.

Ian Axford and Colin Hines (Canada) raise an alternative possibility, of energization by fluid friction at the boundary between the two.

1962 The magnetopause, boundary between magnetosphere and the solar wind, is observed by Explorer 12.
- In July, an H-bomb test ("Project Starfish") by the US above the central Pacific Ocean creates a radiation belt of high-energy electrons, parts of which remain until 1967. The new belt creates aurora at Samoa and unexpectedly knocks out 3 artificial satellites.

1964 IMP-1 (Interplanetary Monitoring Platform 1) reports a large bow shock formed in the solar wind ahead of the magnetosphere, and a long magnetic tail on the night side of the Earth.

- Syun-Ichi Akasofu (Japan-US) and Sydney Chapman revive and expand Birkeland's notion of a "polar magnetic storm", now named " magnetic substorm."

1971 Ionospheric O+ ions found among energetic particles trapped in the Earth's magnetic field, evidence that O+ ions are pulled out of the ionosphere and accelerated

1972 Observations of the diffuse aurora are reported, made by the Canadian spacecraft Isis 2.

1974 A large-scale pattern of "Birkeland currents" between space and the auroral zone traced by Alfred Zmuda and Jim Armstrong, using the Navy's "Triad" satellite.

- David Evans presents evidence that auroral electrons are accelerated within 8000 km or so of Earth.

1977 The S3-3 satellite of the U.S. Air Force observes the upward acceleration of O+ ions, related to the downward acceleration of electrons in the polar aurora.

1981 High resolution auroral images are obtained by the Dynamics Explorer satellite.

1983 ISEE-3 (International Sun-Earth Explorer 3) explores the distant magnetotail, observes that the distant tail plasma flows (past about 70 RE) away from Earth.

1985 An "artificial comet" is produced by a cloud of barium ions, released by the German IRM (Ion Release Module) satellite. Meanwhile another AMPTE spacecraft, CCE (Charge Composition Explorer) observes mass and energy distribution in the ring current, including its peak energies around 65 keV.

[edit] Note to Users

The study of the Earth's magnetosphere is a huge subject, larger than can be covered in a single encyclopedia entry. It was therefore divided into four or five parts, listed below:

Magnetosphere Overview of the Earth's Magnetosphere
Magnetosphere particle motion describes the way the Earth magnetic field guides and traps charged particles.
Magnetospheric convection and magnetic storms about the global flow of plasma and some of the associated physics.
A closely related subject, treated separately:
Aurora (astronomy) about the polar aurora.
Chronology of discoveries and related events:
Magnetosphere history (this entry)