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We often take the most important things for granted. For example, when was the last time you thought about the Earth’s magnetic field? Does the Earth’s magnetic field affect our daily lives in any way other than pointing our compasses north or guiding migratory birds? Are you giving?
Spoiler alert: Every second, Earth’s magnetic field deflects about 1.5 million tons of material that is ejected from the Sun at high speed. If it were not present, the atmosphere would be subject to direct and continuous erosion. We cannot avoid the direct impact of solar particles and they will blow away everything that protects us. Therefore, without Earth’s magnetic field, life as we know it would not exist on Earth’s surface. Of course, our technological society would also be unable to do so, since magnetic fields protect not only DNA but also electronics from the same shock.
Earth (Mercury, Jupiter, Saturn, Neptune, Uranus, etc.) is surrounded by a relatively strong magnetic field that mostly occurs within the planet. At this stage of Earth’s evolution, it is thought to be powered by core cooling and crystallization. This stirs the surrounding liquid iron, creating a powerful electrical current and a magnetic field that spreads through space. This type of magnetic field is known as the Earth’s dynamo, and the structure of the force field that deflects most of the solar wind and forms a protective shield is called the magnetosphere.
To understand more about how it works, let’s travel some 80 kilometers (50 miles) overhead. At that altitude, something fundamental happens. A significant portion of the gas in this region is then ionized. In other words, gas particles have an electrical charge. This is because gas particles typically lose electrons in their structure due to high-energy radiation coming from stars. Charged particles behave in a very special way. They follow magnetic field lines, so they move as if they were in the lanes of a freeway.
Before continuing, it is important to point out that the Sun, like all stars, ejects large amounts of matter in the form of charged particles at very high speeds. This is done in addition to a full range of electromagnetic energy. Our eyes are sensitive to only a very narrow range of visible light. This is what is known as a star wind. In the case of our star, it’s the solar wind. The relationship between the magnetosphere and the solar wind is central to what is known as space weather.
If you could visualize the Earth’s magnetic field, you would see that it is what we scientists call a dipole magnetic field. This is where the lines of force exit one hemisphere and enter the other. The usual convention is that the outgoing magnetic field lines are magnetic north and the incoming magnetic field lines are magnetic south. In the case of Earth, the rules are sometimes reversed, with the magnetic north pole pointing to the south and the magnetic south pole pointing to the north, to avoid confusion with geographic north. In the north, the magnetic field lines point inward, the opposite of what happens with a magnet. This magnetic field is also tilted 11.5 degrees to the planet’s axis of rotation, which defines the geographic north and south poles.
attractive structure
Earth’s magnetic field is twice as strong at the poles as it is at the equator. We know this thanks to instruments on satellites that have investigated both the strength and direction of the Earth’s magnetic field and confirmed its dipole-shaped nature. In addition to being complex, they are also diverse in form. Some of its components are the Van Allen radiation belts, ring currents, magnetotails, and magnetospheric fields.
There are only a few interesting details about the structure of the magnetic field surrounding our planet, but among them are regions that are made up of cold, dense plasma that rotates with the Earth. There are also Van Allen belts, where particles move with relativistic energies, or speeds close to the speed of light.
In what is known as a ring current, high-energy ions move at much slower speeds than in the Van Allen belts, but are denser, creating a current that encircles the Earth. Electrons move from the twilight zone to the night zone, and positively charged ions move in the opposite direction. This ring current creates a magnetic field that points in the opposite direction of the Earth’s magnetic field, and as that field becomes stronger, the strength of the magnetic field measured at the Earth’s surface decreases. More and more ocean currents are connecting the gyres and the ionosphere and play an important role in auroras and space weather.
Understanding the overall makeup of how particles move in our cosmic environment requires another fundamental element. Solar wind is also magnetic. An easy way to visualize this interaction is to imagine the solar wind as a flowing river and the Earth and its magnetic field as a giant rock. Because the solar wind is supersonic, there is a bow shock and a tail behind obstacles. In this case, it’s the magnetic tail. I will leave the discussion of geomagnetic storms and their sources for another time.
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