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Cosmic radiation was already postulated by Victor F. Hess in 1912 to explain the increase in the electric conductivity of the atmosphere with the altitude measured during a balloon flight. Today it is known that this radiation is a high-energy particle radiation from the universe. It is referred to as cosmic radiation.
Development
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The earth’s atmosphere is bombarded by high-energy particles from our galaxy (primary cosmic radiation). In the upper atmospheric layers, these particles react with air molecules. As a result of nuclear reactions, a great number of secondary particles (secondary cosmic radiation) is formed. Some of these secondary particles decay again, are absorbed in the atmosphere or possibly penetrate into the earth. The radiation fluence generated in this way is subdivided into three main components: electrons/photons, hadrons (nuclear components) and myons (heavy electrons). |
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Solar activity
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Solar activity (From: NOAA):
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| Geomagnetic Field: |
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The solar activity is reflected on the one hand in the number of sun spots, on the other hand in the fluence of emitted particles (electrons and protons), the so-called sun wind. Sporadically, very high-energy sun bursts occur in the case of which ultra-high energy protons are also emitted into the universe. When this radiation reaches the atmosphere of the earth, this mostly leads to electromagnetic effects and disturbances as, for example, the polar lights. If this radiation is, however, of particularly high energy, it may enter into the earth’s atmosphere and cause reactions similar to those of the primary cosmic radiation. This can possibly cause an altitude-dependent, local increase in the local dose rate. |
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Composition
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The figure on the left shows that the relative dose fraction at flight altitudes mainly originates from neutrons (n) and electrons and photons (e-) with a smaller proton component (p), whereas myons (µ) and a small fraction of neutrons mainly contribute to the dose on the ground level. This radiation field which is complex at flight altitudes, makes high demands on dosimetry. This is why a reference dosemeter for measurements at flight altitudes was developed at PTB.
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Dependencies
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The amount of radiation exposure due to cosmic radiation at a specific place depends above all on the flight altitude, the magnetic latitude and the solar cycle. The figure on the left shows the local dose rate at an altitude of 10 km. Close to the pole, it is more than twice as high as close to the equator. Additional values can be calculated with the aid of the flight dose calculator.
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Standard values
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| Departure |
Arrival |
Ambient dose
equivalent
H*(10) [µSv] |
Frankfurt
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New York
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37
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| Frankfurt |
Tel Aviv
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11
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| Frankfurt |
Seattle
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48
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| Frankfurt |
Dubai
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19 |
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As examples, the table shows some values of the ambient dose equivalent generated by cosmic radiation on selected flight routes. The dose rate caused by cosmic radiation at sea level amounts to approx. 0.04 µSv/h (this corresponds to approx. 350 µSv/a). |
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© Physikalisch-Technische Bundesanstalt
Page created: 2005-04-15, last update: 2006-06-20, Webmaster
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