Earth's Magnetic Field
Earth is a gigantic magnet with a north pole and a south pole. As a permanent magnet, it is surrounded by a magnetic field. Since the north pole of a magnet corresponds to the north, and since opposite magnets attract each other, the geographic north pole is the magnetic south pole. The geographic and magnetic poles are not located in the same place.
The magnetic south pole is located in northern Canada, about 1000 km from the geographic north pole. Therefore, a compass needle does not point directly north. This deviation of the compass needle varies at each location on Earth. In Poland, the angle of deviation is currently 2.5°. This deviation is caused by the continuous and slow shifting of the magnetic poles. Measurements have shown that the magnetic south pole shifted more than 190 km northwest in five years from 1995 to 2000. Analysis of volcanic rock has revealed that the Earth's magnetic field has reversed polarity multiple times. The strength of the Earth's magnetic field varies across its surface. It is reversed or shielded by magnetically conducting metals found in the Earth's crust, such as nickel, iron, and cobalt. The magnetic field is strongest at the poles.
The Earth's magnetic field is weak compared to the magnetic field of a permanent magnet. A small permanent magnet made of rare-earth metals, such as a samarium-cobalt (SmCo) magnet and a neodymium magnet (NdFeB) supplied by Dhit Ltd., has a field that is several thousand times stronger than the Earth's field. The Earth's magnetic field is generated in a process known as geodynamo. In order for a planet to generate its own magnetic field, it must possess certain properties, such as a sufficiently fast rotation, a fluid interior capable of conducting electric current, and an internal energy source that drives convective currents in the core. The process of generating the magnetic field occurs in the outer part of the Earth's core, where energy from molten iron is transformed into electrical and magnetic energy. The magnetic field induces electric currents, which in turn generate their own magnetic field, creating a feedback loop.
How does Earth's magnetic field protect our planet?
The magnetosphere, our protective magnetic bubble, plays a crucial role in shielding Earth from harmful space influences such as solar wind and radiation. Without the magnetosphere, Earth would be vulnerable to the destruction of its atmosphere and the loss of life-sustaining air, which would be catastrophic for life on our planet.
The magnetosphere also deflects harmful radiation and traps it in regions called the Van Allen radiation belts, providing additional protection from cosmic influences.
However, the magnetosphere is not invincible and can be disturbed during strong space weather events, leading to disruptions in radio and electrical communications and posing a threat to satellites and astronauts in orbit. Examples of such events include the Carrington Event of 1859, which caused a telegraph system failure, and the solar flare of 1989, which resulted in a power outage in Canada.
One of the more positive side effects of magnetosphere disruptions is the appearance of the auroras, which occur above the polar regions of Earth.
The magnetic poles of Earth reverse periodically, with the north becoming the south and the south becoming the north. This phenomenon occurs approximately every 200,000 to 300,000 years, although the last reversal of Earth's poles occurred about 790,000 years ago.
Earth is not the only planet in the Solar System that has a magnetic field. Jupiter, Saturn, Uranus, and Neptune exhibit magnetic fields much stronger than Earth's, although the mechanisms controlling these magnetic fields are not fully understood. Mars lacks sufficient internal heat and a liquid interior required to generate a magnetic field, while Venus has a liquid core but does not rotate fast enough to create a magnetic field.
Magnetic field lines of the Earth's geo-magnetic field radiate from the surface of the globe at various angles relative to the polar axis. The field lines surrounding permanent magnets also have a curved path as they flow from the south pole to the north pole. Since the inclination of a small cylindrical magnet follows the field lines in the same way as a compass needle, we see the pattern of the field with a field sensor, i.e., a compass. This applies to both the extension of the field and its direction.
Magnetism is a mysterious force. We cannot see or feel it. Our senses do not perceive magnetism, yet magnetism has been known to humankind for millennia.
A compass with a steel needle has been used since 1250 BCE. Magnetism continually inspires engineers and scientists to create new applications. The latest generation of high-energy magnets made of rare-earth metals has enabled many more technical applications, such as magnetic levitation used in Japan's maglev trains. Work is still ongoing...
(field sensor, i.e., compass)
The compass follows the magnetic field lines.