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The magnetic field is generated by a feedback loop: current loops generate magnetic fields (Ampère's circuital law); a changing magnetic field generates an electric field (Faraday's law); and the electric and magnetic fields exert a force on the charges that are flowing in currents (the Lorentz force). [58]
The geomagnetic field is generated (and regenerated) as the conducting fluid of the Earth's mantle and core, driven by convection of heat from deeper in the interior, induces an electromotive force (EMF) with the existing magnetic field. This process is very similar to the way an electric generator generates a voltage.
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.
The spacing between field lines is an indicator of the relative strength of the magnetic field. Where magnetic field lines converge the field grows stronger, and where they diverge, weaker. Now, it can be shown that in the motion of gyrating particles, the "magnetic moment" μ = W ⊥ /B (or relativistically, p ⊥ 2 /2mγB) stays very nearly ...
This image shows magnetic declination, or the angle between magnetic and geographic north, according to the World Magnetic Model released in 2025. Red is magnetic north to the east of geographic ...
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.
However, the Earth’s magnetic north is constantly influenced by the planets roiling iron core, which produces the entire magnetic field. As a result, magnetic north is always changing, and since ...
The turtles rely on Earth’s magnetic field to help them navigate in two ways. ... highest-energy cosmic “ghost particle” ever found in an unlikely place: the bottom of the Mediterranean Sea ...