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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.
The Earth's magnetic field protects the Earth from the deadly solar wind and has long been used for navigation. It originates in the fluid motions of the outer core. [24] The magnetic field in the upper atmosphere gives rise to the auroras. [26] Earth's dipole axis (pink line) is tilted away from the rotational axis (blue line).
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 liquid outer core moves in the presence of the magnetic field and eddies are set up into the same due to the Coriolis effect. [18] These eddies develop a magnetic field which boosts Earth's original magnetic field—a process which is self-sustaining and is called the geomagnetic dynamo. [19] Reversals of Earth's magnetic field
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 ...
In 2014, a magnetic field around HD 209458 b was inferred from the way hydrogen was evaporating from the planet. [20] [21] In 2019, the strength of the surface magnetic fields of 4 hot Jupiters were estimated and ranged between 20 and 120 gauss compared to Jupiter's surface magnetic field of 4.3 gauss.
New research indicates the sun’s magnetic field originates much closer to the surface than previously thought, a finding that could help predict periods of extreme solar storms like the ones ...