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Can solar flares be predicted? |
No. For now, solar flares remain impossible to predict. During periods of maximum solar activity, the sun's magnetic field is particularly disturbed, which results in the appearance of many sunspots on its surface. The largest solar flares, which release their energy for several hours, are inherent in the most complex groups of sunspots. More frequent during peak solar activity cycles, solar flares can nevertheless occur at any time. An observation of the sunspots will point to a solar flare a few minutes before it occurs, but its intensity will be impossible to predict.
Solar flares powerful enough to project a flow of particles which can be detected on the ground or on board a commercial aircraft are exceptional . There are only a few per year at the very most.
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Are certain geographical regions more exposed to cosmic radiation? |
Yes. At far latitudes, near the poles, towards which cosmic radiation is deviated by the earth's magnetic field. And at altitude, where the protective layer of the atmosphere is less thick and dense.
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Does travelling at night reduce the dose of radiation that one might receive? |
No. Cosmic radiation comes from throughout our Galaxy. It is both constant and isotropic (identical in all directions), and thus independent of the Earth's rotation.
Though the particles produced by solar flares originally come from the direction of the sun, the earth's magnetic field thoroughly modifies their distribution across the planet's surface. Areas on the "night side" can be more exposed than other areas located on the "day side".
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Does the amount of the dose received differ if we are on the ground or in a plane? |
No. As the altitude increases, the protective layer of the atmosphere becomes thinner and less dense.
In most commercial aircraft, which fly at 10,000 or 12,000 metres, cosmic radiation is 100 to 300 times higher than on the ground. The Concorde, which flies at 18,000 metres, receives radiation which is twice as intense as subsonic flights, but since the flight time is shorter - which reduces the time of exposure to radiation - the dose received during a flight is virtually identical to the one received during a subsonic flight on any given route.
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Can we compare cosmic radiation with medical radiation? |
The average radiation dose during a medical procedure (1.3 mSv/year) is comparable with cosmic radiation (0.4 mSv/year on the ground and up to 5 mSV/year for flight personnel).
However, though the dose delivered during a classical x-ray is comparable with the dose received during a flight, the dose delivered in the event of radiation therapy is far higher.
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What is the Sievert? |
In an effort to express, in a given unit, the risk of the occurrence of deferred effects associated with all possible exposure situations, physicists developed an indicator known as the "effective dose", of which the unit of measurement is the sievert (Sv), named after the Swedish physicist who was one of the pioneers in the protection against ionising radiation. The effective dose is calculated on the basis of the dose (expressed in Gy) absorbed by the various exposed tissues and organs, while applying weighting factors which take into account the type of radiation (a, b, g, X, neutrons), the means of exposure (external or internal) and the specific sensitivity of the organs or tissues (cf. table). By definition, the effective dose, expressed in Sv, can only be used to assess the risk of the occurrence of stochastic effects in man, and cannot be used either for acute effects nor for the effects on fauna and flora.
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Can the Becquerel be used to describe cosmic radiation?
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This unit is only used to describe the activities of radioactive atoms. It can therefore not be applied within the framework of cosmic radiation.
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What kind of dose is required to get cancer?
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There is no radiation dose which will automatically result in the development of radiation-induced cancer in an individual. However, an individual exposed to radiation has a higher stochastic probability of developing cancer, a probability which increases with the dose received.
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Are children more exposed to radiation? |
The exposure is the same for everyone; only the radiation sensitivity differs. As a result of growth, this sensitivity is greater amongst children, given that their cells are renewed more often than in adults. Indeed, dividing cells are the ones which are most affected by ionising radiation, given the particular conformation of their chromosomes, which expose more DNA
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This matter is particularly a concern during pregnancy: it is the embryo which is particularly sensitive to radiation, more so than the mother.
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In the human body, what areas are most sensitive to radiation?
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First of all, those organs with intense cell multiplication: testicles and ovaries, bone marrow, colon, lungs. (cf. table)
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Is a pregnant woman more vulnerable to radiation?
Are their risks for the embryo?
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The embryo undergoes intense cell division, which makes it particularly sensitive to ionising radiation. Exposure to high doses can result in growth problems, mental retardation and various malformations.
Article 10 of the Euratom No. 96-29 directive, transposed into French law in 2001, relates most particularly to protection during pregnancy. Upon informing her employer of her condition, a pregnant woman must no longer be assigned to in-flight duties if the dose received by the unborn child, until the end of the pregnancy, is likely to exceed 1mSV. On board an aircraft, the dose received is a few microsieverts (millionths of a sievert) per hour, which remains far below the values which are likely to cause growth problems, mental deficiency or malformations.
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