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.

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.
References in periodicals archive ?
He received the Tanakadate Prize in 1999 from the Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS) and served as the president of SGEPSS from 2007 to 2009.
The causes behind the forces of nature could then be understood through observations in such fields as meteorology, oceanography, and geomagnetism, thus benefiting all peoples (Barr, 1985).
Appendices list AON projects, state and local government observing activities in Alaska, and volcano, earthquake, geomagnetism observing activities.
Another one of these institutions is the World Data Center for Geomagnetism, Kyoto, Data Analysis Center for Geomagnetism and Space Magnetism Graduate School of Science, Kyoto University, [World Data Center for Geomagnetism, Kyoto, 2005].
El campo internacional de referencia IGRF 2000 [International Association of Geomagnetism and Aeronomy (IAGA, 2000)] fue usado para remover de los valores observados el campo magnetico principal, obteniendose asi las anomalias magneticas [DELTA]T.
The promise of inertial-wave studies,as well as the progress being made in geomagnetism, paleomagnetism, high-pressure physics and seismology, mean that for the first time scientists in these different fields are saying they have something of interest to communicate to one another about the inner earth.
It determines the attitude of mobile devices relative to geomagnetism and gravity and also calculates other aspects of movement such as acceleration, translational speed, and rotational speed.
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The data from this WDC are provided in the format of IAGA (International Association of Geomagnetism and Aeronomy) 2000, in which the magnetic field is represented by four components: Horizontal (H), declination (D), vertical (Z), and total field (F).
Los valores del indice Dst son proporcionados por el World Data Center for Geomagnetism de Kyoto y las variaciones del campo magnetico han sido obtenidas de la base de datos de Intermagnet.
With the present extended sunspot minimum raising questions in peoples' minds about the possibility of a new 'Maunder Minimum', (1) I took out my file of papers on the Sun, geomagnetism and the aurora provided to me by Dr Jean-Paul Legrand of the Institut National d'Astronomie et de Geophysique at St Maur in France.