Solar Radiation Storm Scale

The NOAA Solar Radiation Storm Scale indicates the severity of radiation storms. It is denoted by a S followed by a number from 1 to 5, with 1 being a minor event, and 5 being an extreme event.

The scale uses particle flux as it's physical measure, considering the flux level of particles with energies greater than 10MeV, measured in particles·s-1·ster-1·cm-2.

The scale levels are shown below:

 Category 

  Possible Effects 

S1

Minor

Flux = 101

 Biological: None.

 Other systems: minor impacts on HF radio in the polar regions

 

S2

Moderate

Flux = 102

 Biological: passengers and crew in high-flying aircraft at high latitudes may be exposed to elevated radiation risk.

 Other systems: small effects on HF propagation through the polar regions and navigation at polar cap locations possibly affected.

S3

Strong

Flux = 103

 Biological: radiation hazard avoidance recommended for astronauts on EVA;  passengers and crew in high-flying aircraft at high latitudes may be exposed to radiation risk.

 Other systems: degraded HF radio propagation through the polar regions and navigation position errors likely.

S4

Severe

 Flux = 104

  Biological: unavoidable radiation hazard to astronauts on EVA; passengers and crew in high-flying aircraft at high latitudes may be exposed to radiation risk.

 Other systems: blackout of HF radio communications through the polar regions and increased navigation errors over several days are likely.

S5

Extreme

 Flux = 105

 Biological: unavoidable high radiation hazard to astronauts on EVA (extra-vehicular activity); passengers and crew in high-flying aircraft at high latitudes may be exposed to radiation risk.

 Other systems: complete blackout of HF (high frequency) communications possible through the polar regions, and position errors make navigation operations extremely difficult.