Researchers at the Hungarian Research Network’s Institute for Nuclear Research (HUN-REN ATOMKI) are using an unusual tool — namely, the isotope tritium from ice cores — to investigate the influence of the sun’s magnetic activity on the Earth’s atmosphere. The scientists have just returned from an expedition to the high mountains of Kyrgyzstan, where they collected new samples for their research.
The initial results of this work, based on measurements from previous expeditions, were published this summer in the renowned Journal of Geophysical Research: Atmospheres.
The research is based on the eleven-year cycle of sunspots.
These darker areas on the sun’s surface are protrusions of the solar magnetic field. A strong magnetic field, which occurs during the sunspot maximum, protects the entire solar system from high-energy charged particles (cosmic rays) coming from outside. When the sun’s magnetic field is strong, some of this radiation is deflected. When it is weak (during the minimum), more cosmic particles reach the Earth.
This is where tritium research comes in. Tritium, a hydrogen isotope with one proton and two neutrons, is extremely rare in the upper atmosphere. It is produced there when cosmic rays collide with nitrogen atoms in the air. The tritium binds to hydrogen and enters the Earth’s water cycle as part of water molecules with precipitation.
In permanently cold regions, tritium-containing water falls as snow and is preserved layer by layer in the ice.
Since tritium has a half-life of 12.32 years, the ice cores act as a natural time archive of tritium concentration – and thus indirectly of the intensity of cosmic rays and the solar magnetic field.
To make use of this unique climate archive, ATOMKI researchers are searching worldwide for places where frost prevails continuously. After taking samples in the Alps and Greenland, the latest focus has been on Kyrgyzstan, according to the institute’s press release.
Extracting the ice cores is a real expedition. The staff have to work at high altitudes under extreme, inhospitable conditions. The actual, extremely careful and precise evaluation of the samples then takes place in the comfortable laboratory environment of the research institute. The time-consuming measurements require patience, as the results often take years to become available.
The results published in the summer confirmed the researchers’ hypothesis that there is an anti-correlation between the number of sunspots and the amount of tritium naturally produced in the Earth’s atmosphere.
This means that when there are many sunspots, less tritium is produced, and when there are fewer sunspots, more tritium is produced. This can be explained by the fact that the magnetic field strength of the sun increases during periods of high sunspot activity, which shields some of the cosmic radiation coming from space.
Although the method provides unique insight, there are limitations.
Due to its half-life of 12.32 years, the tritium time series can only be traced back a maximum of about 120 years.
In addition, another historical disturbance must be taken into account. The atomic and hydrogen bomb tests peaked after 1953, releasing artificial tritium into the atmosphere. In order to study natural processes without bias, researchers are therefore focusing on data from before 1953.
The ATOMKI researchers are planning further expeditions to obtain new ice samples in order to create a global picture of natural tritium levels, map the local detectability of the solar cycle, and further refine their observations and model calculations.
Via atomki.hu; Featured image: Pixabay
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