Cosmic radiation
The higher the airplane, the more it's exposed to cosmic radiation.
What does this term mean? Is it safe for passengers and the crew? We'll find out today!
What does this term mean? Is it safe for passengers and the crew? We'll find out today!
Cosmic radiation in aviation
Reading time: ~5-6 minutes
What exactly Cosmic radiation is? It's quite a deep topic, and it requiers understanding of physics to fully capture it.
In short, cosmic radiation is the collective term for the ionising radiation present in the earth’s atmosphere which has originated either from the sun or from outside our solar system (galactic radiation) as Primary Particles or has been created as a result of the interaction of these primary particles with the earth’s atmosphere to create Secondary Particles.
In short, cosmic radiation is the collective term for the ionising radiation present in the earth’s atmosphere which has originated either from the sun or from outside our solar system (galactic radiation) as Primary Particles or has been created as a result of the interaction of these primary particles with the earth’s atmosphere to create Secondary Particles.
What's up today?
Chapter 1
Chapter 4
Description of Cosmic radiation
Galactic cosmic radiation in the local environment of the solar system consists of about 86% positively charged hydrogen nuclei (protons), 11% alpha particles (helium nuclei), 2% electrons (or beta particles) with heavy metal ions and antimatter particles called positrons making up the rest. Within the solar system, lower energy particles are deflected by the magnetic field of the solar wind - the stream of plasma emitted by the Sun.
This follows an 11 year activity cycle which at its maximum output, coincides with increased numbers of sunspots and serves to deflect relatively more of the galactic cosmic radiation component away from the earth with the converse also applying. Whilst its routine effect on cosmic radiation levels is beneficial, the solar maximum is also the most likely time for the generation of Solar Particle Events (SPEs) in which solar flares or coronal mass ejections release large amounts of energy which cannot be forecast although they are short lived - hours to days in duration.
Other types of short term and generally unpredictable solar activity can also vary the magnetic fields of both the sun and the earth and can produce major but very temporary increases in cosmic radiation at aircraft altitudes but they are infrequent and make little difference to the rates of dose accumulation.
This follows an 11 year activity cycle which at its maximum output, coincides with increased numbers of sunspots and serves to deflect relatively more of the galactic cosmic radiation component away from the earth with the converse also applying. Whilst its routine effect on cosmic radiation levels is beneficial, the solar maximum is also the most likely time for the generation of Solar Particle Events (SPEs) in which solar flares or coronal mass ejections release large amounts of energy which cannot be forecast although they are short lived - hours to days in duration.
Other types of short term and generally unpredictable solar activity can also vary the magnetic fields of both the sun and the earth and can produce major but very temporary increases in cosmic radiation at aircraft altitudes but they are infrequent and make little difference to the rates of dose accumulation.
The term "Space Weather" is used to describe all these solar-caused or solar-moderated phenomena.
How Does Total Cosmic Radiation Vary at Aircraft Altitudes?
From the explanation above; the influences on radiation levels at typical aircraft altitudes of around 35000 ft can be summarised. In order of their relative importance, the four main influences are:
atmospheric shielding means that exposure increases as altitude increases. The exposure at aircraft altitudes is about 100 times greater than on the ground, but the increase is not linear and below about 25000 ft altitude, the increase over surface levels is modest. The maximum exposure is reached at 60,000 ft altitude.
the difference in shielding between high and low latitudes has a much more marked effect on exposure at aircraft altitudes than at the surface. At 50° exposure is up to 4 times greater than at the equator.
the 11 year solar maximum reduces exposure by about 25% and the corresponding solar minimum increases it by about 25%. SPE produce large but short-lived increases in exposure which double exposure during their occurrence.
Interesting fact: Cosmic ray visual phenomena, or light flashes (LF), also known as Astronaut's Eye, has been reported by austronauts. Those are spontaneous flashes of light visually perceived by some astronauts outside the magnetosphere of the Earth, such as during the Apollo program. While LF may be the result of actual photons of visible light being sensed by the retina, the LF discussed here could also pertain to phosphenes, which are sensations of light produced by the activation of neurons along the visual pathway
What effect does it have and how is it measured?
Any ionising radiation can displace charged particles, which means that molecules within the cell walls of living organisms can be disrupted. Whilst processes within cells can repair most of this damage, there is, despite a lot of research in the area, considerable uncertainty as to the potential effects to aircrew of exposure to cosmic radiation and it is presently believed that only long term epidemiological studies of their health will better inform our knowledge as to both the degree of risk and the nature of it. Whilst ionising radiation can be objectively measured by absorbed dose - the energy deposited per unit mass - equal absorbed doses of different types of radiation cause biological effects of different magnitudes and the sensitivity of different body tissues to these different types varies.
Neutrons typically contribute up to 50% of the effective radiation dose that aircrew receive as a result of flying whereas occupational exposures of affected ground level workers are more likely to be dominated by gamma radiation and X-rays. The World Health Organisation notes that the biological effects of heightened exposure to ionising radiation attributable to neutrons are not fully understood. Present thinking is based upon the premise that as well as high levels of radiation being harmful, lower levels carry a risk which is proportional to dose.
Neutrons typically contribute up to 50% of the effective radiation dose that aircrew receive as a result of flying whereas occupational exposures of affected ground level workers are more likely to be dominated by gamma radiation and X-rays. The World Health Organisation notes that the biological effects of heightened exposure to ionising radiation attributable to neutrons are not fully understood. Present thinking is based upon the premise that as well as high levels of radiation being harmful, lower levels carry a risk which is proportional to dose.
In 1990, the International Commission on Radiological Protection (ICRP) recommended that flight attendants be considered occupationally exposed to ionizing radiation. This led to the introduction of appropriate monitoring systems in many jurisdictions. In Europe, flight attendants exposed to more than 1 mSv per year must be assessed and informed of potential risks, with expected tactical adjustments to work duties in response to significant exceedance of average exposure levels. This is done to ensure that no flight attendant approaches the internationally accepted limiting effective dose for all ionizing radiation at 20 mSv per year on average over any consecutive five-year period or 50 mSv in any one year.
Although it is considered unlikely that such limits will be reached by flight attendants under any current conditions, the cautious approach to risk taken by some jurisdictions reflects the scientific uncertainty associated with potential cumulative effects of long-term exposure to cosmic radiation on flight attendants
Although it is considered unlikely that such limits will be reached by flight attendants under any current conditions, the cautious approach to risk taken by some jurisdictions reflects the scientific uncertainty associated with potential cumulative effects of long-term exposure to cosmic radiation on flight attendants
Summary
Cosmic radiation is an important topic to understand, especially for those looking to pursue a career in aviation. It can be confidently stated that regular passengers are not at any increased risk, and a week on the beach exposes them to more radiation than a few flights on an airplane.
But for flight and cabin crews, the situation is more complex. Spending each work day in the sky, they are exposed to higher levels of space radiation. In order to determine the safety of such flights, numerous studies have been conducted over the past 30 years with measurements of radiation levels at flight altitudes. They all came to the conclusion that at standard altitudes of around 10 kilometers in Earth's atmosphere, there is still enough protection to shield people from the most harmful types of radiation. And although pilots and flight attendants are undoubtedly more exposed to space radiation, the doses they receive do not exceed dangerous levels.
So, as long as we don't fly in the stratosphere and above, there is no need to worry about constant work in the sky :)
But for flight and cabin crews, the situation is more complex. Spending each work day in the sky, they are exposed to higher levels of space radiation. In order to determine the safety of such flights, numerous studies have been conducted over the past 30 years with measurements of radiation levels at flight altitudes. They all came to the conclusion that at standard altitudes of around 10 kilometers in Earth's atmosphere, there is still enough protection to shield people from the most harmful types of radiation. And although pilots and flight attendants are undoubtedly more exposed to space radiation, the doses they receive do not exceed dangerous levels.
So, as long as we don't fly in the stratosphere and above, there is no need to worry about constant work in the sky :)
Name of article: Cosmic radiation
Release date: 10/12/2023
Acrticle author: Nikita Pavlov
Release date: 10/12/2023
Acrticle author: Nikita Pavlov
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