A) Volcanic activity in the mantle
B) Electric currents in the liquid outer core
C) Interaction of Sun's electromagnetic radiations with the Earth's atmosphere
D) Presence of magnetic elements in the Earth's interior
Correct Answer: B
Solution :
[b] Earth's magnetic field, also known as the geomagnetic field, is the magnetic field that extends from the Earth's interior to where it meets the solar wind, a stream of charged particles emanating from the Sun. Its magnitude at the Earth's surface ranges from 25 to 65 microtesla (0.25 to 0.65 gauss). It is approximately the field of a magnetic dipole united at an angle of 10 degrees with respect to Earth's rotational axis, as if there were a bar magnet placed at that angle at the centre of the Earth. Unlike a bar magnet, however, Earth's magnetic field changes overtime because it is generated by a geodynamo (in Earth's case, the motion of molten iron alloys in its outer core).
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