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Another global field model, called the World Magnetic Model, is produced jointly by the United States National Centers for Environmental Information (formerly the National Geophysical Data Center) and the British Geological Survey. This model truncates at degree 12 (168 coefficients) with an approximate spatial resolution of 3,000 kilometers.
The poles of the dipole are located close to Earth's geographic poles. At the equator of the magnetic field, the magnetic-field strength at the surface is 3.05 × 10 −5 T, with a magnetic dipole moment of 7.79 × 10 22 Am 2 at epoch 2000, decreasing nearly 6% per century (although it still remains stronger than its long time average). [146]
The strongest continuous magnetic fields on Earth have been produced by Bitter magnets. The strongest continuous field achieved solely with a resistive magnet is 41.5 tesla as of 22 August 2017 [update] , produced by a Bitter electromagnet at the National High Magnetic Field Laboratory in Tallahassee , Florida .
Magnetic north versus ‘true north’ At the top of the world in the middle of the Arctic Ocean lies the geographic North Pole, the point where all the lines of longitude that curve around Earth ...
The Earth's magnetic North Pole is currently moving toward Russia in a way that British scientists have not seen before. Scientists have been tracking the magnetic North Pole for centuries ...
These magnetic fields are a hundred million times stronger than any man-made magnet, [11] and about a trillion times more powerful than the field surrounding Earth. [12] Earth has a geomagnetic field of 30–60 microteslas, and a neodymium-based, rare-earth magnet has a field of about 1.25 tesla, with a magnetic energy density of 4.0 × 10 5 J/m 3.
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.
One of Earth’s deepest mysteries lies beneath our feet: the planet’s inner core. Made of iron and nickel, the hot, solid sphere is about 70% the size of the moon.