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Magnetic declination (also called magnetic variation) is the angle between magnetic north and true north at a particular location on the Earth's surface. The angle can change over time due to polar wandering .
Changes over time scales of a year or more mostly reflect changes in the Earth's interior, particularly the iron-rich core. These changes are referred to as secular variation. [1] In most models, the secular variation is the amortized time derivative of the magnetic field , ˙.
Changes in Earth's magnetic field on a time scale of a year or more are referred to as secular variation. Over hundreds of years, magnetic declination is observed to vary over tens of degrees. [13] The animation shows how global declinations have changed over the last few centuries. [34] The direction and intensity of the dipole change over time.
Its speed can also change drastically—from 1999 to 2005, for example, magnetic north shifted from moving only nine miles in a year to 37 miles. However, in the past five years, magnetic north ...
Geomagnetic secular variation refers to some changes in the Earth's magnetic field. The field has variations on timescales from milliseconds to millions of years – its rapid ones mostly come from currents in the ionosphere and magnetosphere. The secular variations are those over periods of a year or more, reflecting changes in the Earth's core.
The north magnetic pole moves over time according to magnetic changes and flux lobe elongation [3] in the Earth's outer core. [4] In 2001, it was determined by the Geological Survey of Canada to lie west of Ellesmere Island in northern Canada at 81°18′N 110°48′W / 81.300°N 110.800°W / 81.300; -110.800 ( Magnetic North Pole
Polar drift is a geological phenomenon caused by variations in the flow of molten iron in Earth's outer core, resulting in changes in the orientation of Earth's magnetic field, and hence the position of the magnetic north- and south poles. The North magnetic pole is approximately 965 kilometres (600 mi) from the geographic North Pole. The pole ...
The dynamo theory describes the process through which a rotating, convecting, and electrically conducting fluid can maintain a magnetic field over astronomical time scales. A dynamo is thought to be the source of the Earth's magnetic field and the magnetic fields of Mercury and the Jovian planets.