Sunday, August 1, 2021

The geomagnetic field

Earth's magnetic field, also known as the geomagnetic field, is the magnetic field that extends from the Earth's interior into space, where it interacts with the solar wind, a stream of charged particles that emanate from the Sun. The magnetic field is generated by electrical currents due to the movement of convection currents from a mixture of molten iron and nickel in the Earth's outer core: these convection currents are caused by heat leaving the core, a natural process called geodynamics.

The magnitude of the Earth's magnetic field at its surface ranges from 25 to 65 microteslas (0.25 to 0.65 gauss).[3]  As an approximation, it is represented by a field of a magnetic dipole currently tilted at an angle of about 11 degrees to the Earth's axis of rotation, as if there were a huge magnet placed at that angle through the center of the Earth.  The north geomagnetic pole, located in 2015 on Ellesmere Island, Nunavut, Canada, in the northern hemisphere, is actually the south pole of the Earth's magnetic field, and vice versa.

 While the north and south magnetic poles are generally located close to the geographic poles, they move slowly and continuously across geological timescales, but slowly enough that common compasses continue to be useful for navigation.  However, at irregular intervals of several hundred thousand years, geomagnetic inversion occurs and the north and south magnetic poles, respectively, abruptly change places.  These geomagnetic pole reversals leave a valuable rock record for paleomagnetists in calculating geomagnetic fields in the past.  This information, in turn, is useful in studying the movements of continents and the ocean floor in the process of tectonic plates.

 The magnetosphere is the region above the ionosphere that is defined by the extent of the Earth's magnetic field in space.  It stretches several tens of thousands of kilometers into space, shielding the Earth from charged particles in the solar wind and cosmic rays that would otherwise destroy the upper atmosphere, including the ozone layer that shields the planet from ultraviolet radiation.

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