The Earth has two shields that shield it from space hazards - the atmosphere and a magnetic field. If both were gone, there would be no more life on the blue planet. With the sometimes gigantic magnetic field, a lot is in motion. Recently, there has been repeated speculation as to whether the Earth's magnetic poles could reverse in the long term and weaken the field. But how likely is that, and what would that mean?
According to the European space agency ESA, the Earth's magnetic field is a complex and dynamic force that protects our planet from cosmic rays and charged particles from the sun. "We assume that the earth's magnetic field is a relatively chaotic process," says Jürgen Matzka, an expert in geomagnetism from the German Research Center for Geosciences (GFZ) in Potsdam.
A pole reversal would be long overdue
Solar storms are not only responsible for the fascinating polar lights that just appeared over Germany. In our high-tech world, they can also cause considerable damage and disrupt satellites in particular. High-energy particles and a plasma cloud race from the star in the center of the solar system the 150 million kilometers to our home planet within a short time.
Unlike the geographic poles, the earth's magnetic poles are by no means rigid. Statistically, the recurring process of pole reversal is long overdue, according to Matzka. "The last polar reversal, that was quite a long time ago, about 780,000 years." That is longer than the long-term average of 300,000 to 500,000 years. However, there are also phases in which there has been no reversal for millions of years.
According to Matzka, the fact is: "We have known since 1840 that the overall magnetic field strength is decreasing." This is mainly due to the fact that in the southern hemisphere in the areas of South Africa, the South Atlantic and South America the field is declining particularly sharply. In the South Atlantic it is around 30 percent weaker than would be expected. In Europe, however, it is increasing again.
"We have some very good reconstructions of the Earth's magnetic field going back in time, and you can see again and again that the strength of the field changes very often and very strongly, or that there is a polarity reversal," says Matzka. "I would not see it now from the facts that we have indications of a reversal." However, the weaknesses in the southern hemisphere could be initial factors for a reversal.
At the last field reversal there were no modern humans on earth, so there are no records of them. However, according to Matzka, oceanic sediment cores may provide clues. There have always been indications that a polar reversal can influence evolution or species extinction. Thus, finds of certain fossils end up exactly at the points in the drill cores where a field reversal was detected. However, most of the results would show a rather small influence.
Solar activity is increasing again
Things are different in our high-tech age. The risks for satellites are increasing. In the event of solar storm warnings, systems there would have to be shut down, says Matzka. "There is certainly also the possibility, if we are hit by a particularly strong event, that there will be more damage than one can imagine at the moment."
"The magnetic field anomaly in the South Atlantic has always been a challenge for satellites in low Earth orbits, since high-energy protons can influence the satellite electronics there," says Melanie Heil, coordinator of the space weather mission at the ESA site in Darmstadt. Under certain conditions, the satellites could be exposed to radiation more frequently.
The so-called solar activity is currently increasing again in its eleven-year cycle. According to Heil, the maximum can be expected in 2025. However, the weakening of the magnetic field is not so strong that a noticeable effect on the effects of solar storms can be expected.
The magnetic field created in the outer core of the earth cannot really be seen or heard. According to Esa, scientists at the Technical University of Denmark have converted magnetic signals measured by an Esa satellite mission into sound. The result: the "language" of the vital field is less protective than threatening.