Earth Magnetic Field, The Invisible Magnetic Field
In all space, around and inside the Earth there is a magnetic field. Some natural or man-made phenomena add up and form a total magnetic field, which varies constantly depending on the variation of the source that produced it. The Earth Magnetic Field is a protective screen against high-energy particles from the cosmos, the magnetic field is strongly influenced by extraterrestrial weather events, which can disrupt all terrestrial technological systems. These kind of studies made it possible to understand the internal structure and dynamics of the Earth and the phenomena that occur in the upper atmosphere and in outer space.
The Earth already had a magnetic field 3.45 billion years ago. Back then, the intensity was only 50 to 70% of its current value. But 3.2 billion years ago, Earth’s magnetic field was as strong as it is today. In fact, it is very difficult to be certain in this area.
Earth’s magnetic field existed 4.2 billion years ago
In 2020, MIT work contradicted results published in 2014, based on the magnetization of ancient zircon crystals and showing that the Earth’s magnetic field existed 4.2 billion years ago.
Although magnets have been known since ancient times, it was the Chinese who, around 1000-1100, first used them for self-direction: this was the birth of the compass.
Why is it important?
The Earth’s magnetic field protects us from the solar wind and cosmic rays. It forms a protective screen against particles from the cosmos. This field is part of a vast ensemble which surrounds the Earth and which is called the magnetosphere. It is constantly deformed by the force of the solar wind.
Origin of the magnetic field: GEODYNAMO
The Earth’s magnetic field is generated mainly inside the Earth, by the dynamo effect of convection movement in the Earth’s core, which is 90% molten iron.
This type of movement is produced by the progressive cooling of the dense core and the seed located in the center of the Earth.
This produces a dipolar magnetic field, tilted about 10° with respect to the Earth’s axis of rotation.
A small part of the Earth’s magnetic field comes from magnetic rocks in the Earth’s crust. Analysis of the magnetization of seabed rocks in particular makes it possible to highlight a polar reversal, which occurs approximately once every million years.
Solar X-rays and ultraviolet radiation are absorbed in the upper layers of the atmosphere, where ion-electron pairs are produced on the sunlit side of the earth.
These free particles generate electrical currents at an altitude of about 100 km, which is responsible for the diurnal variations of the magnetic field.
The outermost part of Earth’s magnetic field is exposed to the solar wind, a stream of charged particles that the sun constantly emits. Magnetospheric electric currents also cause the observed magnetic field variations on the ground.
DRIFT OF THE MAGNETIC POLE
The magnetic north and south poles, defined as points on the earth’s surface where the magnetic field is exactly vertical, are not antipodes.
The North Magnetic Pole is located in the Far North of Canada, while the South Magnetic Pole is outside the French base of Dumont d’Urville in Antarctica. The secular variations of the Earth’s magnetic field produce a slow displacement of the magnetic poles. Thus, the north magnetic pole is currently moving at a speed of 55 km/year towards Siberia.
SHIELD OF PROTECTION FOR LIFE
The magnetosphere, created by the Earth magnetic field and it has played an important role in the development of life on Earth.
This happened by deflecting high-energy particles from the solar wind and cosmic rays. This allows Earth’s atmosphere to persist over time, unlike on Mars where, in the absence of a strong magnetic field, the solar wind blew through much of the planet’s atmosphere. Aurora Borealis and Australis | Why is the northern lights different from the southern lights?The shielding provided by the Earth’s magnetosphere has reduced the flux of high-energy radiation reaching the ground, allowing life to be sustained on Earth.
The sun alternates between periods of calm and periods of increased activity. In periods of high solar activity, a person can have solar flares that cause a sharp increase in UV and X-ray radiation from the sun, as well as the speed of the solar wind. So we can have magnetic storms on Earth. The charged particles enter the cavities created by the Earth’s magnetic field, giving rise to spectacular phenomena: the northern and southern lights.
These natural phenomena can have serious consequences on human technological systems:
- Satellite damage
- Disturbances in telecommunications systems: satellites, submarine cables, etc.
- Degradation or interruption of satellite positioning services, eg. gps or galileo
- Increased radiation received by astronauts and aircraft passengers
- Current induced in the oil pipe, accelerates its wear
- Currents parasites in the electrical grid, which can cause power outages in large areas
Photo credit (main picture): NASA / NASA’s Goddard Space Flight Center Scientific Visualization Studio