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The magnitude of Earth's magnetic field at its surface ranges from 25 to 65 μT (0.25 to 0.65 G). [3] As an approximation, it is represented by a field of a magnetic dipole currently tilted at an angle of about 11° with respect to Earth's rotational axis, as if there were an enormous bar magnet placed at that angle through the center of Earth.
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.
A magnetic field (sometimes called B-field [1]) is a physical field that describes the magnetic influence on moving electric charges, electric currents, [2]: ch1 [3] and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to the magnetic field.
The term geophysics classically refers to solid earth applications: Earth's shape; its gravitational, magnetic fields, and electromagnetic fields ; its internal structure and composition; its dynamics and their surface expression in plate tectonics, the generation of magmas, volcanism and rock formation. [3]
The following examples are listed in the ascending order of the magnetic-field strength. 3.2 × 10 −5 T (31.869 μT) – strength of Earth's magnetic field at 0° latitude, 0° longitude; 4 × 10 −5 T (40 μT) – walking under a high-voltage power line [9] 5 × 10 −3 T (5 mT) – the strength of a typical refrigerator magnet
magnetic flux density, magnetic induction: tesla: T = Wb/m 2 = N⋅A −1 ⋅m −1: kg⋅s −2 ⋅A −1: Φ, Φ M, Φ B magnetic flux: weber: Wb = V⋅s kg⋅m 2 ⋅s −2 ⋅A −1: H magnetic field strength ampere per metre: A/m A⋅m −1: F magnetomotive force: ampere: A = Wb/H A R magnetic reluctance: inverse henry: H −1 = A/Wb kg − ...
The average magnetic field in Earth's outer core is estimated to measure 2.5 milliteslas (25 gauss), 50 times stronger than the magnetic field at the surface. [44] The magnetic field generated by core flow is essential to protect life from interplanetary radiation and prevent the atmosphere from dissipating in the solar wind.
If the Earth's magnetic fields were exactly dipolar, the north pole of a magnetic compass needle would point directly at the North Geomagnetic Pole. In practice, it does not because the geomagnetic field that originates in the core has a more complex non-dipolar part, and magnetic anomalies in the Earth's crust also contribute to the local ...