geomagnetism


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geomagnetism:

see magnetismmagnetism,
force of attraction or repulsion between various substances, especially those made of iron and certain other metals; ultimately it is due to the motion of electric charges.
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geomagnetism

(jee-oh-mag -nĕ-tiz-ăm) The Earth's magnetic field (or its study), which at the Earth's surface approximates that of a bar magnet at the center of the Earth with its axis inclined by 11.4° to the Earth's rotation axis and somewhat off-centered: the north magnetic and geographical poles are much closer together than the south poles. Both sets of poles wander in position. The strength of the magnetic field varies from 0.6 gauss near the magnetic poles to 0.3 gauss near the equator, i.e. from 60–30 microtesla, but can depart by up to 20% from the average without any correlation with major surface features. The dipole field changes only slowly with time but there are larger local variations in strength and direction. Violent short-term fluctuations occur during geomagnetic storms. Studies of magnetized rocks show that the entire magnetic field has reversed in direction about twice every million years in the past 165 million years. Complete reversals (i.e. north pole switching from pointing toward geographic north to pointing south, or vice versa) can occur within a few thousand years. The source of the geomagnetic field is believed to lie in a complex dynamo action in the Earth's liquid iron-rich outer core. Convective motion in this rotating electrically conducting fluid, in the presence of a magnetic field, generates electric currents; these in turn induce a magnetic field. Hence the Earth's field has been maintained. The field existed since at least 2.5, probably 3.5, thousand million years ago. See also magnetosphere; ring current.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006

geomagnetism

[¦jē·ō′mag·nə‚tiz·əm]
(geophysics)
The magnetism of the earth. Also known as terrestrial magnetism.
The branch of science that deals with the earth's magnetism.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Kuznetsov, "Effect of a self-induced electric field on the electron beam kinetics and resulting hard X-ray and microwave emissions in flares," Geomagnetism and Aeronomy, vol.
Together with the magnetic concentrator, this enables mapping of geomagnetism data in three dimensional vectors for analysis.
Alan Thomson, head of geomagnetism at the British Geological Survey, said: "There's a feeling it's not as intense as first thought.
"Our current view is that the effect of the solar flare is likely to reach Earth later today (Thursday GMT), possibly tomorrow morning," said Alan Thomson, head of geomagnetism at the British Geological Survey (BGS).
It, too, has vastly different energetic patterns that all collaborate to make it work in its entirety and which are known to scientists as forms of geomagnetism' (166).
First, the digital animals needed the ability to respond to a direction-linked environmental cue, of the sort provided in reality by temperature, geomagnetism, wind and chemical gradients.
(8) Implementacion del modelo IGRF-10 de la IAGA (International Association of Geomagnetism and Aeronomy) http://recursos.gabrielortiz.com/calculadora_declinacion/ entrada.asp
Carter (history of science, Duke U.) argues that the British Empire provided a broad setting where universal sciences such as geomagnetism and meteorology could be practiced and legitimized, both helping to overcome the inherited problems of the inductive method, and setting up a system by which scientists could study interconnected phenomena on a global scale.
Basham, P., and Newitt, L.R., 1993, A historical summary of Geological Survey of Canada studies of earthquake seismology and geomagnetism: Canadian Journal of Earth Sciences, v.
However, the orientation/navigation of moths at night may involve not just the moon or other celestial light sources, but many other phenomena such as geomagnetism, gravity or barometric, acoustic, olfactory and terrestrial visual cues (Riley and Reynolds, 1986; Frank, 1988) and the presence of a strong source of artificial light may confuse the insects into ignoring such factors.
Its geomagnetic sensor, which acts as an electronic compass, detects direction and movement by analyzing the vector of geomagnetism and gravitational pull.