The Threat of Solar Cosmic Radiation Storms: Guidance for Pilots
ALPA members may be exposed to higher levels of cosmic radiation at certain times than the general public who spend most of their time below the clouds. Read on to learn more about the threats of solar cosmic radiation storms and guidance for reducing exposure.
Low levels of ionizing radiation are a normal part of the environment, and substances that emit ionizing radiation are present in each cell of the human body. Everyone is exposed to ionizing radiation that originates from outside the solar system (known as galactic cosmic radiation) and from our Sun (known as solar cosmic radiation), but the Earth’s magnetic field normally shields us from much of the effects of that radiation. This shielding effect decreases with increases in altitude and latitude.
A solar particle event, such as a solar flare, leads to a temporary increase in solar cosmic radiation levels. A severe disturbance in the Sun can lead to radiation outputs that penetrate the Earth’s magnetic field and enter the atmosphere, increasing the dose rate of ionizing radiation for air travelers. While the increased dose rate of solar cosmic radiation is usually very small relative to the rate of galactic cosmic radiation, on rare occasions it can significantly exceed it. The time and amount of this increase is difficult to accurately predict and may last from a few minutes to more than a day. The increased radiation dosage is greatest near the magnetic poles, where the Earth’s magnetic field provides the least shielding, and the dosage is lowest near the geomagnetic equator.
Radiation exposure is usually expressed in terms of “sieverts.” One sievert equals 1,000 milliseverts (mSvs). The FAA-recommended limit for an aircrew member over a five-year average is 20 mSvs per year with no more than 50 mSvs in a single year. An average member of the U.S. population receives 3 mSv of ionizing radiation from all sources annually; pilots receive on average an additional 3 mSv each year for a total of 6 mSv, which is well below the FAA-recommended maximum exposure. Online calculators, like this one from the FAA, are available to help an individual determine the amount of solar cosmic radiation, measured in mSvs, that a particular route(s) at a given altitude and time-at-altitude creates.
Reducing Pilot Exposure to Solar Cosmic Radiation
ALPA has compiled the following list of suggested guidance and resources for your use to reduce your exposure to solar radiation events:
- Check with your company on its guidance and operational procedures for limiting solar cosmic radiation exposure.
- Sign up for e-mailed solar radiation alerts from the National Oceanic and Atmospheric Administration (NOAA). There are five NOAA radiation alert categorizations ranging from S1, Minor to S5, Extreme. The recommended response to counter increased radiation exposure risk is to minimize flight time at altitudes that exceed the recommended maximum flight altitude.
- Learn more about radiation advisories on NOAA’s aviation community dashboard.
- Check out the FAA’s Office of Aerospace Medicine, Civil Aerospace Medical Institute (CAMI) calculator for galactic radiation received in flight. This can be used to determine the amount of galactic radiation for a given flight(s) in a specified period.
- Take a free lesson online to learn more about this subject at Space Weather Impacts on Aviation.
- What Aircrews Should Know about Their Occupational Exposure to Ionizing Radiation, DOT/FAA/AM-03/16, Office of Aerospace Medicine, October 2003
- Inflight Radiation Exposure, Advisory Circular 120-61B, Federal Aviation Administration, November 11, 2014
- Centers for Disease Control and Prevention (CDC) Radiation and Your Health: Addresses solar, galactic, terrestrial and medical radiation (and nuclear testing), health effects, and a primer on radiation
- Aircrew Safety and Health–Ionizing Radiation, by the National Institute for Occupational Safety and Health (part of the CDC)
- Aircrew Exposure to Cosmic Radiation, a webpage maintained by the United Kingdom’s Civil Aviation Authority, which takes a much more proactive role than the FAA on monitoring aircrew radiation, particularly for pregnant women
- Radiation Protection: Evaluation of the Implementation of Radiation Protection Measures for Aircrew, an in depth paper by the European Commission’s Directorate-General for European Transport