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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.
The strongest are primarily geomagnetically induced currents, which are induced by changes in the outer part of the Earth's magnetic field, which are usually caused by interactions between the solar wind and the magnetosphere or solar radiation effects on the ionosphere. Telluric currents flow in the surface layers of the Earth.
It created strong auroral displays that were reported globally and caused sparking and even fires in telegraph stations. [1] The geomagnetic storm was most likely the result of a coronal mass ejection (CME) from the Sun colliding with Earth's magnetosphere. [2] The geomagnetic storm was associated with a very bright solar flare on 1 September 1859.
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 intersection between the magnetic and rotation axes of the Earth is located not at the Earth's center, but some 450 to 500 km (280 to 310 mi) away. Because of this asymmetry, the inner Van Allen belt is closest to the Earth's surface over the south Atlantic Ocean where it dips down to 200 km (120 mi) in altitude, and farthest from the Earth ...
A geomagnetic excursion, like a geomagnetic reversal, is a significant change in the Earth's magnetic field.Unlike reversals, an excursion is not a long-term re-orientation of the large-scale field, but rather represents a dramatic, typically a (geologically) short-lived change in field intensity, with a variation in pole orientation of up to 45° from the previous position.
The Earth's Magnetic North Pole is actually considered the "south pole" in terms of a typical magnet, meaning that the north pole of a magnet would be attracted to the Earth's Magnetic North Pole. [2] The north magnetic pole moves over time according to magnetic changes and flux lobe elongation [3] in the Earth's outer core. [4]
Geomagnetic secular variation refers to changes in the Earth's magnetic field on time scales of about a year or more. These changes mostly reflect changes in the Earth's interior, while more rapid changes mostly originate in the ionosphere or magnetosphere. [1] The geomagnetic field changes on time scales from milliseconds to millions of years.