Magnetic Pole
A magnetic pole refers to the points at either end of a magnetic field where the magnetic force is most intense, designated as north and south. These poles are not aligned with the Earth's geographic poles, as they shift over time due to the dynamic movement of molten iron and nickel in the Earth's outer core. The Earth's magnetic field, which acts like a giant bar magnet, is crucial for navigation, as compass needles align with it, pointing toward the magnetic poles. The magnetic field also protects the planet from harmful solar radiation, deflecting charged particles and creating phenomena like auroras.
Recent studies indicate that the Earth's magnetic poles are moving at an increasing rate, with the Northern Magnetic Pole shifting toward northern Siberia and the Southern Magnetic Pole moving toward Australia. Scientists have noted that the magnetic field is weakening, raising concerns about a potential polar reversal, a natural process in which the magnetic poles switch places. This event, though historically significant, typically occurs over thousands of years and is not expected to drastically impact life on Earth, despite possible disruptions to human-made systems like GPS. Understanding these magnetic dynamics is essential for comprehending both Earth’s geological processes and their implications for technology and navigation.
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Magnetic Pole
A magnetic pole is a point at either of the two ends of a magnetic field where the magnetic force is at its strongest. The poles are designated as north or south, corresponding to the approximate geographic direction in which each pole lines up. Magnetic poles with opposite charges attract each other, while similar charges repel.
On the surface of Earth, the magnetic poles are the regions toward which compass needles point and where the planet's magnetic field lines are vertical. Earth's magnetic poles are not located at the true geographic north or south poles, but move over time, driven by forces within the planet's interior.
Background
Magnetic forces are generated at the subatomic level by electrically charged particles known as electrons. Electrons spin like tops as they rotate around the nucleus of an atom. This spin generates an electrical current that gives the electron the potential to gain magnetic properties. Because most atoms are made up of paired electrons that spin in opposite directions, the electrical force cancels itself out. In certain substances such as iron, cobalt, or nickel, the electrons are not paired and spin in the same direction. This gives the substance a magnetic field, an area around the object that exhibits magnetic force. If the substance comes in contact with another magnetic object, its electrons line up and the substance becomes magnetized. The direction of the spinning electrons determines the direction of the magnetic field.
Magnetic force is concentrated at the opposite ends, or poles, of a magnetic field. The poles were given the names north and south because one end of a magnetized substance seemed to point to the geographic north and the other south. Since opposite charges attract each other, the magnetic field leaves a magnet at the north pole and enters at the south pole. The movement of the magnetic field is represented by magnetic field lines, which move outward from one pole, curve in a ring-shaped arc, and fall back in at the other pole.
Overview
Compass needles and the poles of smaller magnets line up in a particular direction because they are reacting to the force generated by Earth's magnetic field. The field is believed to be created by the movement of molten iron and nickel in the planet's outer core, a layer about 1,800 miles below the surface. This magnetic field gives Earth the properties of a giant bar magnet, with magnetic field lines leaving from one pole, traveling over the equator, and entering through the opposite end. At the poles, the magnetic field lines are aligned in a vertical direction. However, the actual magnetic poles are not antipodal and are distinct from the geomagnetic poles, which are antipodal and based on the theoretical model of a basic dipole generating the Earth's magnetic field.
Earth's magnetic poles are also not aligned with the true north and south points on the planet. The geographic poles are located 90 degrees north and south from the equator at the spots where Earth's axis intersects with the surface. In 2005, the Northern Magnetic Pole was located near Ellesmere Island in northern Canada, about 500 miles from the geographic North Pole; the Southern Magnetic Pole was just off the coast of Antarctica about 1,750 miles from the South Pole. Because of the swirling movements of Earth's molten outer core, the magnetic poles shift over time, moving at a rate of about 25 miles per year (though through the first two decades of the twenty-first century the rate was faster, about 34 miles per year). By 2020, the Northern Magnetic Pole had steadily moved farther to the north and west, headed in the direction of northern Siberia. The Southern Magnetic Pole was moving in the direction of Australia. Scientists update the World Magnetic Model every five years to account for this shift—although in 2019 an early update was required due to the faster than expected pace of movement.
The magnetic field created by the planet extends about 370,000 miles above the surface and protects Earth from radiation and electrically charged particles emitted by the Sun. Without a magnetic field, the particles would strike the surface directly and have a devastating effect on life. The field lines deflect the particles toward the magnetic poles, where they interact with atoms in the upper atmosphere causing a phenomenon known as auroras, also called the northern or southern lights.
Data collected by a satellite array launched in 2013 by the European Space Agency (ESA) showed that Earth's magnetic field is weakening at a rate of about 5 percent a decade. It had previously been weakening at a rate of 5 percent a century. Scientists believe the effect is being caused by the magnetic poles getting ready to "flip" alignments. The process has occurred many times in the history of Earth, usually at intervals of about 200,000 to 300,000 years. This timeframe means Earth is overdue for another polar reversal, as the last one occurred about 750,000 years ago. Scientists have estimated the next switch could begin in less than 2,000 years, and some suggest observed phenomena may be the early signs of instability preceding a reversal. Flips in the magnetic poles, however, do not happen quickly; they are thought to take hundreds or thousands of years to complete the transition. One study released in 2019 estimated that the last reversal in fact took approximately 22,000 years, even longer than previously believed.
If a polar reversal was completed, compass needles in the Northern Hemisphere would no longer align themselves to geographic north. They would also flip polarity and point toward the south. There is little chance the new alignment would have a major effect on the planet's protective magnetic field, at least on a human timescale. Even though it is weakening as the shift nears, the field is still strong enough to deflect any harmful solar radiation. The fossil record also shows no adverse planetary effects from previous magnetic pole reversals, although some theories have suggested the events may cause stress to some species or trigger greater chance of genetic mutation. On the other hand, human-made systems that rely on the Earth's magnetic field, such as GPS and radio communications, would potentially be disrupted by changes to the magnetic field. However, most scientists suggest that the lengthy period of growing instability before a reversal would likely allow plenty of time for such systems to be protected or adapted.
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