What is GEOMAGNETISM?
Scientists believe that Earth’s magnetism arises from electric currents generated by the movement of hot liquid iron in its core. The currents create a magnetic field with invisible lines of force flowing between Earth’s geomagnetic poles. These are not the same as the North and South Poles and, more significant, they are not stationary. The geomagnetic poles mark the ends of the axis of Earth’s magnetic field. In 1971 a group of scientists investigating a 30,000-year-old aboriginal campsite in Australia discovered that the fire’s heat had allowed iron particles in the stones to realign with Earth’s magnetic field at the time. What’s more, the iron particles pointed south, indicating that magnetic north at that time must have been somewhere in the Antarctic. The discovery confirmed other recent reversals of the Earth’s magnetic field. It is now understood that major reversals in Earth’s magnetic field occur about every half million years. Shorter flips, lasting a few thousand to 200,000 years, occur at other times. These reversals are clearly recorded in the rocks created in the seafloor’s Mid-Atlantic Ridge, which are carried away from the ridge by shifting ocean-floor plates.
Earth’s magnetic field dominates a region called the magnetosphere which wraps around the planet and the atmosphere. Solar wind-charged particles flowing from the sun-presses the magnetosphere against Earth on the side facing the sun and stretches it on the shadow side Nevertheless, some particles of solar wind do leak through and are trapped in the Van Allen belt. When they hit atoms of gas in the upper at atmosphere near the geomagnetic poles. they produce the eerie light displays that are called auroras
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