What is Earth’s Magnetic Field and how is it Manifesting?

What is Earth’s Magnetic Field and how is it Manifesting?

Earth’s Magnetic Field ensures smooth movement of Earth and protects us from foreign threats like cosmic rays and solar wind.

The magnetic field of Earth, also known as Surface Magnetic Field, is defined as a magnetic dipole having one pole near the geographic North Pole while the other one resides near the geographic South Pole. It originates from the core of the Earth and goes several kilometers into space to deflect the cosmic radiations that are thrown by the Sun. These charged particles are so powerful that they will blow the ozone layer away.

This could lead to a serious catastrophe as the ultraviolet radiations are extremely harmful to humans. Cosmic rays can also burn the atmosphere of a planet and our neighbor, Mars, is a prime example of that.

Its magnitude ranges from 25 to 65 microteslas at the surface of the Earth. The North geomagnetic pole, located in the Northern Hemisphere near Greenland, is actually the south pole of the Earth’s magnetic field. Similarly, the South geomagnetic pole is the north pole of the surface magnetic field. The source of this magnetic field comes from the convection currents of the molten iron found in the outer core of the Earth. The inner parts of the core provide the necessary heat for these currents.

The name given to this natural mechanism is Geodynamo. According to a general perception, the positions of both the magnetic poles remain stagnant but that’s not true.

They can move as much as 40 kilometers every year and this movement is not dependent on each other. Hence, these poles are not at directly opposite positions on the globe. Due to this continuous wandering of the magnetic field, the effect is reversed over a period of hundreds of thousands of years. Both magnetic poles switch places and all the information about this massive reversal is recorded in the rocks. The reason for this is that the polarity of the Earth’s magnetic field is stored in igneous rocks.

Centered stripes appearing on the mid-ocean ridges are used for identifying the reversal of the field. Paleomagnetists calculate the past track of the motions of continents and ocean floors through this data. As the crust of the Earth is also magnetized by this field, it is quite helpful to determine the locations of metal ores.

According to the initial theory, the poles of a magnet were defined by the Earth’s magnetic field. This means that the north pole of the magnet will be attracted by the North Magnetic Pole of the Earth. But as we know that opposite poles attract each other, it was deduced that the North Magnetic Pole is actually the south pole of its magnetic field. There are two possible ways to define a magnetic pole. The local definition of a pole is determined by measuring the inclination with respect to its magnetic field.

In case of Earth, the inclination at the North Pole is 90o downwards while the South Pole experiences an inclination of -90o in the upwards direction. For sake of a global definition, a line, parallel to the best-fitting magnetic dipole, is drawn through the center of the Earth. The points of intersection will become the magnetic poles of the planet.

The intensity of the Earth’s geomagnetic field is decreasing continuously and the rate of deterioration has increased many times in the past few years. This has raised serious concerns that the field might reverse. A weak area in the Earth’s magnetic field, called South Atlantic Anomaly, has also expanded. It stretches from Zimbabwe to Australia and this has exaggerated the fears of the scientific world. An international team of researchers joined forces to study this case and published their findings in the Proceedings of the National Academy of Sciences. Richard Holme, a Professor of Geomagnetism at the University of Liverpool summarized his findings in the following words:

There has been speculation that we are about to experience a magnetic polar reversal or excursion. However, by studying the two most recent excursion events, we show that neither bear resemblance to current changes in the geomagnetic field and therefore it is probably unlikely that such an event is about to happen. Our research suggests instead that the current weakened field will recover without such an extreme event, and therefore is unlikely to reverse.”   

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