Are solar / geomagnetic storms real risks for commercial aviation?

Question

Background

Solar storms/flares are solar events sending particles in space that are potentially dangerous on Earth. From Wikipedia:

Solar flares strongly influence the local space weather in the vicinity of the Earth. They can produce streams of highly energetic particles in the solar wind, known as a solar proton event. These particles can impact the Earth's magnetosphere (see main article at geomagnetic storm), and present radiation hazards to spacecraft and astronauts. Additionally, massive solar flares are sometimes accompanied by coronal mass ejections (CMEs) which can trigger geomagnetic storms that have been known to disable satellites and knock out terrestrial electric power grids for extended periods of time.

^Source

They are rated by the US NOAA on a scale from 1 to 5. For instance, level 3 events occur about once a year:

S3 (Strong) - Biological: radiation hazard avoidance recommended astronauts on EVA. Passengers and crew in commercial jets at high latitudes may receive radiation equivalent to approximately 1 chest x-ray.

There are also geomagnetic storms listed on the same page.

Question

Is this a real risk for commercial aviation, if so how do airlines treat this risks on affected routes, e.g.:

• How are airlines informed?
• Are pilot-in-command informed and allowed to veto a flight?
• What do they do regarding exposed crews and passengers?

Answer 1

Minor, typical solar flares do not pose a significant risk to aviation. Flight planning services, such as LIDO, do not typically include specific information on solar flares or solar activity.

Airlines that require specific information on solar activity for their flight operations would typically refer to these specialised space weather services, such as the Space Weather Prediction Centre (SWPC).

Regulation: Regulations, such as EU-OPS (EASA), mandate the assessment and management of crew's exposure to cosmic radiation, especially during heightened solar activity. Airlines must monitor solar activity and adjust flight paths or altitudes to minimise radiation exposure. The crew's exposure is tracked to ensure it remains within safe limits. During periods of increased solar activity, advisories may lead to operational changes, such as altering flight routes, particularly over polar regions. The FAA has issued Advisory Circulars that provide information and guidance on measuring and managing crew exposure to cosmic radiation.

While minor solar flares generally do not significantly impact aviation, a major solar event, akin to the Carrington Event of 1859, could have considerable implications:

Impact on Plane’s Avionics: Aircraft are designed to be resilient against electromagnetic interference, and many modern aircraft are shielded against solar radiation. However, a solar flare of the magnitude of the Carrington Event could significantly disrupt satellite-based systems like GPS, important for navigation. Aircraft are also equipped with Inertial Reference Systems (IRS/INS), but navigational accuracy would deteriorate.

Impact on Radio Communications: Such a solar event could disrupt the ionosphere, affecting VHF and HF communications. Increased solar radiation and charged particles could lead to elevated radio noise and interference, challenging the clarity and reliability of VHF communications.

Impact on Supporting Infrastructure: An event similar to the Carrington Event could induce geomagnetic currents, disrupting power grids and causing widespread electrical blackouts. This could significantly impact air traffic control and airport operations, especially in busy airspace and at major airports.

In conclusion, while the aviation industry is not significantly affected by minor solar flares, a major solar event may cause significant disruption with pronounced impacts on safety - aircraft less precise in their navigational position with potentially limited air traffic control communications.

Answer 2

A pilot in command can always veto, scrub, or divert a flight. Per the Federal Aviation Regulations FAR 91.3(a), "The pilot in command of an aircraft is directly responsible for, and is the final authority as to, the operation of that aircraft." This applies to airline operations (air carriers, FAR Part 121), air taxis and charters (FAR Part 135), and general aviation (FAR Part 91) operations.

A much bigger issue than than the radiation exposure for the people will be the atmospheric effects of the radiation, and how the radiation affects, e.g., satellite navigation. A very strong solar flare can require shutting down some on-orbit satellites to avoid damage—including navigation satellites, such as GPS. A very strong solar flare can ionize the atmosphere to the point it interferes with communications, especially in the HF band used for transoceanic communications.