In our daily lives, we overlook many of the fundamental elements that make life on Earth possible. One of the most ignored, yet essential, is the terrestrial magnetic field, an invisible force that surrounds us like a true spatial shield. This field not only guides us through compasses, but also plays a vital role in protecting us from harmful effects of the Sun.
You may never have thought about it, but without this invisible shield surrounding our planet, life as we know it simply wouldn't exist. And that's no exaggeration: Every second, the Earth's magnetic field deflects more than a million tons of solar particles which, if not stopped, could wipe out the atmosphere and collapse all our technological systems. More information on this can be found at Our article on the Earth's magnetic field.
What is the Earth's magnetic field and how is it generated?
The Earth's magnetic field, also known as geomagnetic field, is a force that arises because of the movement of the outer core of the planet, composed mostly of molten iron in constant agitation. This movement generates large-scale electric currents which give rise to a magnetic field that extends from the interior of the Earth to outer space. If you want to better understand how it works, you can consult the article on how the Earth's magnetic field works.
This phenomenon is known as geodynamo, and is responsible for the Earth behaving like a huge magnet where the lines of force They emerge from one pole and enter through the other. Interestingly, in the current convention, the magnetic north pole points towards the geographic south and vice versa, which often causes confusion.
Furthermore, the magnetic axis is not perfectly aligned with the planet's geographic axis, but is tilted by about 11,5 degrees. This tilt gives the Earth's magnetic field a dipolar shape, but its structure is much more complex than it appears at first glance. To learn more about the relationship between the sun and the Earth's magnetic field, I invite you to read How the Sun affects the Earth's magnetic field.
The magnetosphere: our shield against outer space
The magnetic field extends beyond the atmosphere and forms the magnetosphere, a huge structure that acts as a barrier against the solar wind, a constant stream of charged particles emitted at high speed by the Sun. If this wind were to directly impact Earth, the atmosphere would gradually erode, and the effects on living beings and electronic devices would be devastating.
In this region, a fraction of the gas is in the form of ionized plasma, that is, with charged particles that interact directly with the magnetic field. These particles move along the field lines, as if traveling on invisible highwaysIt is thanks to this phenomenon that structures such as the Van Allen radiation belts and magnetic glue of the Earth. To learn more about the auroras, you can visit the article that reveals how the northern lights are generated.
Within the magnetosphere there are several relevant zones:
- Van Allen Belts: regions where particles move at almost the speed of light.
- Ring current: an electric current around the planet formed by energetic ions moving at high density. This current contributes to temporarily reduce the intensity of the field measured at the surface.
- Cold and dense plasma in synchronized rotation with the Earth.
This entire interconnected system between the magnetic field and the solar wind forms what is known as space climate, a set of phenomena ranging from auroras to geomagnetic storms that affect telecommunications and power grids. For more details on the consequences of solar storms, you can read What would happen if the Sun's magnetic field reversed?.
How solar particles behave: auroras and magnetic storms
Solar particles, when deflected by the magnetic field, often impact the polar regions where the field lines are most open. It is in these places where the northern and southern lights, a luminous spectacle that is not only aesthetic, but also a warning of the constant energetic bombardment that surrounds us.
When a large amount of solar matter reaches the Earth—as occurs during solar storms—it can pass through the magnetosphere and cause what is called a geomagnetic stormThese storms can impact:
- Electrical networks (as happened in Quebec in 1989).
- GPS and telecommunications systems.
- Satellites and space stations, whose components can be damaged by overexposure to radiation.
- Aircraft on routes near the poles, which sometimes have to be detoured as a precaution.
The study of these phenomena has made it possible to anticipate these solar events and prepare the systems responsible for controlling critical infrastructures so that they can better resist its effectsIf you want to know more about space storms and their effects, check out the article on space hurricanes.
The growing threat of the South Atlantic Anomaly (SAA)
One of the most worrying peculiarities of the Earth's magnetic field is the existence of areas where its intensity is significantly minimized. The best known is South Atlantic Anomaly (SAA), a region that covers part of South America and the South Atlantic Ocean.
In this area, the magnetic shield is located so weakened that satellites that pass over it are exposed to a more intense bombardment of solar particlesThis can cause failures in your electronic systems, data loss, or even permanent damage. If you're interested in this topic, check out the article on the reversal of the magnetic poles.
The worrying thing is that This anomaly has not only persisted, but appears to be expanding. and even splitting into two distinct areas, making monitoring even more difficult. Some theories point to irregularities in the composition of the Earth's core as a possible cause.
The reversal of magnetic poles: a cyclical phenomenon
Another of the most intriguing questions is the possibility of a total reversal of the magnetic polesAlthough it may sound apocalyptic, this is a natural phenomenon that has occurred many times in the geological history of the planet.
The last reversal took place about 780.000 years ago. Scientists believe we are in the midst of a similar process, although its duration can extend for centuriesDuring this time, the magnetic field can weaken, change shape, and generate multiple temporary poles.
What implications would this have? Although it would not represent a direct threat to life, there is greater exposure to solar and cosmic radiation on the surface, which could affect species that rely on the magnetic field for orientation, such as certain birds, sea turtles, or sharks. To learn more about the implications of this phenomenon, you can read the article that discusses How are northern lights formed.
Scientific missions to understand the Earth's magnetic shield
To study all these dynamics, Various space agencies have launched specific missions in recent years, among which stand out:
- Swarm (ESA): Three satellites launched in 2013 that monitor the magnetic signals of the core, mantle, crust, and atmosphere.
- THEMIS (NASA): A mission that discovered that there are two main areas where solar particles pass through the magnetic field most easily.
- Magsat, CHAMP and Cluster: Previous and complementary missions that allowed mapping the magnetic field and detecting anomalies such as the one in the South Atlantic.
These missions allow the development of models such as IGRF (International Geomagnetic Reference Field), regularly updated to reflect observed changes and used by navigation and guidance systems around the world. If you are interested in the structure of the atmosphere in relation to the magnetic field, I recommend reading on the structure of the atmosphere.
Beyond Earth: The heliosphere as our last shield
Beyond the magnetosphere, another layer of protection comes into play: the heliosphereThis gigantic magnetic bubble extends beyond the orbit of Pluto and is generated by the solar wind emitted by the Sun. Serves as a shield against cosmic radiation from other stars.
For a long time, it was thought that its shape was similar to that of a comet, with a long tail. But new simulations, based on data from missions such as Voyager and IBEX, have revealed that the heliosphere is more like a compact croissantThis discovery is important for understanding how much of that cosmic radiation manages to sneak into the Solar System.
The mission Interstellar Mapping and Acceleration Probe (IMAP), scheduled for launch in 2024, aims to expand this information and help design future space missions that are better protected against the dangers of deep space.
Thanks to current scientific research, we know today that the Earth's magnetic field is not only essential for life, but also a dynamic and constantly evolving structureAlthough invisible, its impact is tangible: it protects our satellites, electrical systems, navigation technologies, and, of course, our very existence from the relentless bombardment of space. Therefore, understanding its behavior and anticipating its changes is not only interesting but absolutely crucial for the future of humanity.
