C H A P T E R

N ° 30

Aircrews and Mitigation Measures

Modern aircrafts are designed with shielding and redundancy in their systems. Yet, radiation exposure to pilots and crew onboard aircrafts located at higher latitudes caused by space weather is still a concern.

Activities occurring on the Sun (i.e., solar activity) can create space weather influencing the performance and reliability of space-borne and ground-based technological systems. Additionally, in some instances, it can even endanger human life and health.

The aviation industry has been subject to space weather impact numerous times with significant financial losses. In 2005, the total cost of extra fuel used to reroute aircrafts from polar routes due to space weather amounted to approximately 186 million USD. This was excluding costs to passengers and compensation. The increased cross-polar traffic and financial losses makes space weather a recognized natural hazard within this critical infrastructure.

In Hoplon’ articles; C H A P T E R N ° 27-29, we provide an introduction to the relation between space weather and the aviation industry, exploring the interaction between space weather and the Earth’s natural planetary defence systems, and avionics. Additionally, we discuss the associated risks of financial losses caused by space weather impact and mitigation measures.

In today’s article, we will look closer at the relation between space weather and aircrews. Additionally, we will explore some of the financial impact space weather could have on the aviation industry. Lastly, we introduce some of the currently available mitigation measures and discuss the effectiveness of radiation protection measures.

The near-Earth space environment

The impact from space weather on the aviation industry is not limited to its electronics. During certain space weather events, enhanced number of particles (i.e., Solar Energetic Particles (SEPs)) originating from the Sun, and complex interplanetary magnetic field from the Sun bursts out into the outer space environment.

* Solar Energetic Particles (SEPs) are high-energy and charged/ionized particles originating from the Sun. *

If Earth-directed, the particles can penetrate through the outer and inner Van Allen radiation belts and, thus, the slot-region (i.e., the ‘safe´-regions) closest to Earth, and interact with the already present Galactic Cosmic Rays (GCRs) between the inner radiation belt and Earth.

* The Van Allen Radiation belts are two regions of energetic charged particles within the near-Earth space environment, mostly originating from the solar wind, that are trapped by the Earth’s magnetic field. The belts are named after physicist James Van Allen and pose a challenge for space travel and space infrastructure due to the radiation they contain. *

* Galactic Cosmic Rays (GCRs) are high-energy particles originating from outside the solar system, primarily from within our galaxy, the Milky Way. The particles mostly comprise of protons and atomic nuclei, and travel at nearly the speed of light, possessing tremendous energy. Galactic Cosmic Rays are thought to be accelerated by events like supernovae and coalescing neutron stars. *

* To learn more about solar energetic particles (SEPs) and the Van Allen belts, please read: C H A P T E R N ° 5-6. *

During this process, the Solar Energetic Particles (SEPs) enhances the overall energy level of the particles within this region. This can produce momentarily high radiation levels and exposure lasting from hours to several days, making the space environment closest to Earth more hazardous.

Increased energy levels of particles, increases the risk of radiation particles entering the Earth’s atmosphere.

**Image Credit:** Unknown: *Illustration showing the Van Allen Belts.*

The South Atlantic Anomaly (SAA)

The aviation industry is becoming more aware of the impact of space weather on flight operations due to the increase of cross-polar traffic. The industry is primarily concerned about risks during high-latitude (>50°N) and polar operations (>78°N). This is due to the South Atlantic Anomaly (SAA).

The Earth’s magnetic field originates deep within its core between the molten outer core and the solid mantle, and extends past the surface into space. Here, it acts as a protective shield surrounding the planet and repels and traps charged particles emitted by the Sun.

However, Earth’s magnetic field is not truly dipolar in space or at the Earth’s surface, consequently causing the internal magnetic field to have a depression point centered over South America and the southern Atlantic Ocean. This weak region is known as the ‘South Atlantic Anomaly’ (SAA), and brings the Van Allen radiation belts closer to Earth, enabling solar radiation particles to travel closer to the Earth’s surface in this weaker field region. This consequently makes satellites orbiting in the first orbital class named ‘Low Earth Orbit (LEO)’, and aircrafts more susceptible to space radiation exposure.

**Image Credit:** F. Ginisty et al.: *Map showing the magnetic field strength of Earth.*

Elevated aviation radiation exposure

Air transportation experiences the highest amount of radiation exposure compared to other terrestrial transportation modes. This particularly applies to aircraft operations taking place at high altitudes where; shielding from the Earth’s magnetic field and atmosphere is reduced; around the South Atlantic Anomaly (SAA); and during longer routes, such as over the Polar Regions.

Aircrafts operating at only a few hundred kilometers above the Earth’s mean surface level can, thus, experience a substantial amount of radiation exposure, making them exceed their annual radiation dose level limits faster. Exposure to high radiation levels increases the risks of long-term health issues.

Under the absence of space weather, aircrews are routinely exposed to higher levels of cosmic radiation (i.e., Galactic Cosmic Rays (GCRs)) at flight altitudes. Galactic Cosmic Rays originate from deep space and the Sun, and are a part of the always present background radiation in the space environment.

However, the background radiation can get intensified during solar events. Solar activities can release large bursts of high-energy particles in the form of Solar Energetic Particles (SEPs). These particles have a higher energy level, making them capable of interacting with the already present radiation particles in the near-Earth space environment. This interaction can increase the energy level of the already present background radiation, making the near-Earth space environment more hazardous. Furthermore, if the Solar Energetic Particles (SEPs) are intense enough, they are able to penetrate through the Earth’s magnetic field, significantly increase the radiation levels at flight altitudes, consequently exposing avionics and aircrews to radiation.

Solar Energetic Particles (SEPs) can pose health risks as they carry enough energy to damage cells. Energetic particles can directly interact with and damage DNA molecules, in worse cases leading to mutations or even cell death. Similarly, they can damage cells, causing them to no longer function correctly or make them become cancerous.

The severity of the damage depends on the type and energy of the particle. The effects from exposure to Solar Energetic Particles (SEPs) can range from mild and recoverable acute effects, such as changes to the blood, nausea, or vomiting, to more severe and long-term effects, like cataracts, increased cancer risks, and reduced fertility.

Financial losses

In 2015, Daniel Matthiä et al. from the German Aerospace Center (DLR) Cologne, Germany, investigated the economic impact and effectiveness of radiation protection measures in aviation during ground level enhancement on the 13’th of December 2006. Daniel Matthiä et al. investigation suggest that lowering flight altitudes from 12.4968 km (41.000 ft) to 8.5344 km (28.000 ft) for a transatlantic flight travelling from Seattle to Cologne would give a maximum reduction in the effective radiation dose levels by 42%. This would make a decrease from 1.199 μSv (microsievert) to 68.7 μSv (microsievert). However, in order to reduce the radiation dose level, fuel consumption was increased by 4.8% (from 53.9 to 56.5 tons) and an extension of flight duration by 4.7% (from 9.9 to 19.37 hours).

* μSv stands for ‘microsievert’, and is a unit of measurement for radiation dose, specifically one millionth of a Sievert (Sv). *

Furthermore, according to an investigation made in 2021 by Moe Fujita et al. from Aioi Nissay Dowa Insurance, the annual risks associated with the countermeasure costs mentioned above indicates a potential economic loss of approximately 1.295 euros for daily operated long-distance flights. Moreover, the investigation suggests that a Ground-Level Enhancement (GLE) event significant enough to cause a change in flight conditions occur approximately once every 47 years when following dose and dose-rate regulations. This is, however, reduced to once every 17 years under more strict conditions.

In order to mitigate the radiation hazard flight altitude, restrictions have to be imposed. However, flight altitude restrictions or rerouting shows an increase in the fuel consumption for twin-engine, wide-body jet passenger aircrafts by 33%–58% (39–69 tons). When applying the constraints to aircraft altitudes and latitudes, the flight time and fuel consumption increases by 17-20% (2.2–2.8 hours) and 27-41% (32–48 tons), respectively.

When comparing different studies, the lowest financial loss - with the radiation exposure dose being the parameter - is estimated to be approximately 3.892 euros (4.556 USD) and 299.055 euros (0.35 million USD). This is for a flight from Tokyo to London with an aircraft operating at an optimal altitude for minimal radiation exposure and aircraft speed. Taking the same parameters but applying it to space weather events like the 2003 Halloween Storm with a radiation exposure level of 500 μSv (microsievert), the flight cancellations suggest to amount in a financial loss of 49.97 million euros, whereas a radiation exposure level of 1000 μSv (microsievert) would cause flight cancellations amounting in a loss of 2.77 million euros.

Mitigation measures

To mitigate radiation exposure to aircrews, certain measures can be taken.

Aircrews are generally considered occupational radiation workers globally. This classification arises from their significant exposure to ionizing radiation at high altitudes from Galactic Cosmic Rays (GCRs) and Solar Energetic Particles (SEPs).

This classification requires aircrews to adhere to the rules and regulations for radiation workers, such as a yearly radiation exposure dose limits. The regulatory bodies suggest limits such as 20 mSv (millisievert) per year averaged over 5 years for aircrews. For the general public it is suggested to not exceed 1 mSv (millisievert) per year, with a specific radiation limit of 0.5 mSv (millisievert) during pregnancy.

These regulations require airline dispatchers to consider cumulative crew radiation when scheduling flights.

Other currently available mitigation strategies are to simply not fly. During severe and extreme space weather events, most aircrafts are restricted from liftoff, due to the high risks associated with space weather impact. This is both due to its potential of significantly affecting aviation systems and procedures, and due to the high level of radiation exposure to aircrews.

Furthermore, in cases where the space weather event is considered to impose moderate risks, aircrews may be permitted to fly. Yet, only by lowering their altitudes or rerouting.

The currently available mitigation measures are not financially or environmentally sustainable, nor are they necessarily resilient.

The South Atlantic Anomaly (SAA) is currently causing no visible impact on daily life on the surface of Earth. Additionally, the weakening of the Earth’s magnetic field intensity (i.e., strength) is still within what would be considered ´normal variations´.

However, recent observations and forecasts indicate that the region is expanding westwards, and that the magnetic field intensity is decreasing. In addition, data from 2015-2020 indicate that the South Atlantic Anomaly (SAA) is starting to divide into two cells, consequently creating additional challenges for infrastructure such as transportation, particularly air transportation. Whereas rerouting aircrafts is currently a possible ´quick fix´ and, thus, a temporary mitigation measure, new strategies could be necessary due to this change.

Furthermore, lowering flight altitudes or rerouting aircrafts are not sustainable mitigation measures. Both demands an increase in fuel consumption, consequently causing significant economic losses and CO2 emissions adding to the issue of environmental contamination.

Additionally, lowering an aircrafts altitude is not risk free, and being able to create a restriction for aircrews to liftoff is a privilege that may not always be possible to uphold. Sustainable mitigation measures, thus, have to be in place in cases where a liftoff is necessary.

Moreover, while classifying aircrews as radiation workers is helpful, as it makes them adhere to the national/international radiation exposure dose level restrictions, the extent of their exposure is often not well-documented or regulated in many countries. Being aware of the individual annual radiation dose level of the aircrew is essential in order to minimize the potential health risks posed by space radiation exposure.

Lastly, as explained in Hoplon’ previous articles focused on space weather impact on the aviation industry, there are several backups and mitigation procedures for avionics depending on how flight-critical a system is.

*Flight-critical refers to aspects of a flight that are essential for safety and must be handled with utmost care. It encompasses critical phases of flight, critical parts of an aircraft, and critical tasks in maintenance, all of which, if compromised, could lead to serious consequences, such as accidents or even fatalities. *

However, as technology progress, flight electronics are becoming smaller, consequently increasing their vulnerability to space weather impact. The advancement of aviation technology and the interdependencies within critical infrastructure, increases the risk and vulnerability of space weather impact on not only the aviation industry, but likewise on all critical infrastructures. Infrastructure in which the aviation industry depends on.

While the easiest mitigation measure for aircrafts and aircrews is to simply not fly, issues arise for those that are for example already in air when space weather events occur. Mitigation procedures are in place in those instances. Yet, a situation where an aircrew is onboard a non-well-functioning non-reliant aircraft naturally increases the risk of safety issues. Thus, despite there being certain mitigation measures for aircrew and avionics, the aviation industry is not immune to the risks associated with space weather impact, and the need for research and mitigation measures remain.

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