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Thus, the Earth's magnetic field had to be explained by localized sources, and as more was learned about the Earth's field, these sources became increasingly complex. [2] At first, in both China and Europe, the source was assumed to be in the heavens – either the celestial poles or the Pole star.
Earth's magnetic field, also known as the geomagnetic field, is the magnetic field that extends from Earth's interior out into space, where it interacts with the solar wind, a stream of charged particles emanating from the Sun.
Edmond Halley (English, 1656–1742) – first chart of Earth's magnetic field; Christopher Hansteen (Norwegian, 1784–1873) – produced the first charts of the intensity of the Earth's magnetic field; Harry Hammond Hess (American, 1906–1969) – seafloor gravity anomalies and theory of seafloor spreading
Study of Earth's magnetosphere began in 1600, when William Gilbert discovered that the magnetic field on the surface of Earth resembled that of a terrella, a small, magnetized sphere. In the 1940s, Walter M. Elsasser proposed the model of dynamo theory, which attributes Earth's magnetic field to the motion of Earth's iron outer core.
The magnetic field of a magnetic dipole has an inverse cubic dependence in distance, so its order of magnitude at the earth surface can be approximated by multiplying the above result with (R outer core ⁄ R Earth) 3 = (2890 ⁄ 6370) 3 = 0.093 , giving 2.5×10 −5 Tesla, not far from the measured value of 3×10 −5 Tesla at the equator.
From these experiments, he concluded that Earth was itself magnetic, and that this was the reason why compasses point north (previously, some people believed that it was the pole-star Polaris, or a large magnetic island on the north pole that attracted the compass). He was the first person to argue that the center of Earth was iron, and he ...
“Especially in the outer core where Earth’s magnetic field is generated.” The new analysis not only filled an important data gap—it also revealed new clues about that period’s magnetic ...
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. 1964 - Syun-Ichi Akasofu (Japan-U.S.) and Sydney Chapman revive and expand Birkeland's notion of a "polar magnetic storm", now named "magnetic substorm."