The Earth’s magnetic field protects its surface and its inhabitants – including all humans with their fragile bodies, as well as sensitive electronics – from deadly cosmic rays and charged particles flying from the Sun.
However, in some places, this invisible armor is weakening and the gaps grow. Therefore, scientists from all over the world are very carefully studying such anomalies in order to better understand the mechanics of the magnetohydrodynamic dynamo in the bowels of the planet, as well as to predict changes in the magnetic field.
A magnetic anomaly is a significant weakening of the Earth’s magnetic field over a specific region on the planet’s surface. As the name suggests, the South Atlantic (SAA) is located over the southern part of the Atlantic Sea, partially “covering” South America and “catching its tail” in the very south of Africa. This formation has the largest size at an altitude of about 500-600 kilometers. At sea level, its “projection” is somewhat less and manifests itself in the magnitude of the magnetic field – it is equal to that at an altitude of about a thousand kilometers above those areas of the earth’s surface where there are no anomalies.
Such a decrease in the magnetic field is not yet dangerous for the inhabitants of our planet, but it already creates serious problems for the engineers who design spacecraft and control their missions. For example, the legendary Hubble orbiting telescope revolves around the Earth just at an altitude of about 540 kilometers – that is, several times a day it flies through the anomaly. At these minutes, the work of the space laboratory is suspended due to the increased level of radiation.
The trouble is, where the Earth’s magnetic field weakens, the protection of the entire space around the planet from the solar wind and galactic rays decreases. Charged particles get the opportunity to rush to the earth’s surface almost without deviating, and, naturally, collide with everything that comes their way. Moreover, for spacecraft, the situation with the South Atlantic anomaly is further complicated by the structure of the radiation belts. It is in this region of the Atlantic that the inner Van Allen belt descends almost to the surface of the planet.
The Van Allen radiation belts are two kind of Earth blankets formed from charged particles (protons and electrons) that are trapped between the magnetic field lines of our planet. Usually, most satellites are located below the inner belt (orbits up to 1000 km at apogee) and are almost not exposed to the destructive effects of ionizing radiation. But the South Atlantic anomaly still spoils the nerves of astronauts and engineers in the rocket and space industry.
In addition to the Hubble, which has to periodically stop scientific work, many other vehicles are victims of this area in near-earth space: the ISS carries increased radiation protection, since it also flies through this anomaly, presumably several Globalstar satellites were damaged, and on the shuttles they were completely ordinary laptops shut down. For people, the flight through the anomaly at an altitude of 400 kilometers above the Earth also does not pass unnoticed – most of the phosphenes (flashes behind closed eyes that cause high-energy elementary particles) are observed by astronauts and cosmonauts over the Atlantic.
What caused this unpleasant behavior of the magnetic field – the question is not completely closed. According to the generally accepted and well-proven theory, the liquid metal core of the Earth, during its rotation and constant mixing of convection currents, works like a dynamo. But, since its structure is inhomogeneous, different masses of matter move in the bowels of the planet at slightly different speeds. These fluctuations are superimposed on the misalignment of the magnetic axis with the axis of rotation of the planet and “result” in a weakening of the magnetic field over the south of the Atlantic.
Modern research shows that the South Atlantic Anomaly has been more or less stable for at least 8 million years and is smoothly drifting westward at a speed of about 0.3 degrees per year. This coincides with the difference in the speed of rotation of the earth’s surface and the outer layers of the planet’s core. But what is most interesting is that the SAA changes its shape and gradually splits into two parts. This process has been going on for a long time and in a number of sources two separate anomalies are initially considered – Brazilian and Cape Town.
On the general health of the planet, such changes, as far as can be judged, do not have a serious impact. Problems only arise when a person climbs higher above the surface – there are more satellites in orbit, and their design increasingly uses common commercially available components. How serious will be the effect of increased radiation on those devices that fall into the anomaly during or after a strong solar storm, only time can tell.