BRUSSELS – The Earth is constantly bombarded by high-energy charged particles called cosmic rays. We are usually protected from this barrage by the magnetosphere, but this shield can sometimes weaken.
Scientists at the General Assembly of the European Geosciences Union present new information about a “journey” that occurred 41,000 years ago during which the magnetic field of our planet diminished and harmful space rays bombarded the Earth.
The Earth’s magnetic field protects our planet from the onslaught of cosmic radiation flowing through space and also from charged particles thrown out by the Sun, but it is not constant. Not only does magnetic north oscillate away from true north (a specific geographic location), but it sometimes flips. During these reversals, north becomes south and south becomes north, and in this process the strength of the magnetic field decreases.
But there are also what are called “magnetic field excursions”, which are short periods in which the intensity of the magnetic field decreases and the two magnetic poles of the magnetosphere can disappear, to be replaced by a large number of magnetic poles.
During these periods, called magnetic field excursions, the strength of the magnetic poles also weakens, which means that our planet is less protected from cosmic rays at these times.
The “Lachamp voyage,” which occurred about 41 thousand years ago, is among the best studied magnetic field voyages.
This event is characterized by a low intensity of the magnetic field, which means less protection of the Earth’s surface from harmful space rays. Periods of low magnetic field intensity can be associated with major disturbances in the biosphere, the entire area of our planet in which life exists, ranging from mountaintops to the deepest ocean trenches.
To find out when cosmic rays were intensely bombarding the Earth’s surface, scientists can measure the abundance of different isotopes (isotopes of chemical elements are atoms of the same chemical element that have the same atomic number but differ in atomic mass due to the different number of neutrons).
These isotopes are produced by the interaction between cosmic rays and the Earth’s atmosphere.
Times of lower paleomagnetic field intensity should be associated with higher rates of production of cosmic radionuclides (cosmic isotopes) in the atmosphere.
When cosmic rays hit particles in Earth’s atmosphere, they create showers of isotopes called “cosmic radionuclides” that rain down on our planet’s surface. These elements accumulate over time in sediments, which scientists can study after they are recovered from the sea floor and in ice samples extracted from regions such as Antarctica and Greenland.
Sanja Banovska, a researcher at the German Geosciences Center (GFZ) in Potsdam, studied the relationship between the strength of the Earth’s magnetosphere and the concentration of cosmic radionuclides, such as “beryllium-10,” during the “Lachamp flight.”
It was found that the average production rate of the isotope “beryllium-10” during the “flight” was twice higher than the current production, which means that the intensity of the magnetic field was very low and many cosmic rays reached the Earth’s atmosphere.
“Understanding these extreme events is important for their future occurrence, space-based climate predictions, and assessing impacts on the environment and the Earth system,” Banovska said.
Source: Space
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2024-05-01 04:23:16