Do solar storms make flying more dangerous?
Occasionally, and mainly on high-latitude routes. NOAA rates solar radiation storms from S1 to S5, and from S2 upward it warns that passengers and crew in high-flying aircraft at high latitudes may be exposed to elevated radiation risk. NOAA counts about 25 S2 storms in an 11-year solar cycle, and stronger ones less often.
Updated
NOAA's solar radiation storm scale
| Level | For aircraft, NOAA says | About how often |
|---|---|---|
| S1 Minor | No biological effect | 50 per cycle |
| S2 Moderate | High-latitude passengers and crew may be exposed to elevated radiation risk | 25 per cycle |
| S3 Strong | High-latitude passengers and crew may be exposed to radiation risk | 10 per cycle |
| S4 Severe | High-latitude passengers and crew may be exposed to radiation risk | 3 per cycle |
| S5 Extreme | High-latitude passengers and crew may be exposed to radiation risk | Fewer than 1 per cycle |
Source: NOAA Space Weather Scales. A storm's level is set by the flux of energetic protons near Earth.
Why high latitudes
Particles from the sun carry much less energy than galactic cosmic rays, so Earth's magnetic field turns them away everywhere except near the magnetic poles. The FAA notes that solar cosmic radiation dose rates are negligible near the geomagnetic equator and that the increase during an event is greatest near the poles (AC 120-61B, 3g and 6a). A flight from Singapore to Sydney barely notices a solar storm; a flight from New York to Hong Kong over the Arctic can.
What airlines can do
The FAA's Civil Aerospace Medical Institute runs a solar radiation alert system with data from NOAA's Space Weather Prediction Center. Responding to an alert by flying at a lower altitude can significantly reduce exposure on high-latitude routes, especially if the response is quick (AC 120-61B, 6a and 9b).
Why the numbers on this site leave them out
CARI-7, the FAA's model, calculates the dose from galactic cosmic radiation using the sun's monthly state. The FAA says the dose an individual might receive during a solar particle event cannot be estimated in advance (AC 120-61B, 9a). So every route dose on this site, and every dose the FlightDose app calculates, is the galactic cosmic radiation dose; a flight through a strong storm at high latitude would receive more. The FlightDose app shows NOAA's current scales and says so while a storm is in progress.
See where the high-latitude routes run on the dose-rate map, or read how the solar cycle changes every flight's dose.
Sources
- NOAA Space Weather Prediction Center. NOAA Space Weather Scales.
- Federal Aviation Administration. Advisory Circular AC 120-61B, In-Flight Radiation Exposure, 2014.
Know before you fly the pole
FlightDose pulls NOAA's Kp index, the R, S and G storm scales and active alerts, and shows the sun itself in NOAA's imagery.
FlightDose calculates your exact flight.
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