The level of danger from the fluxes of energetic protons from solar flares

Possible effects of space weather disturbances on a scale NOAA

Solar proton events Flux level of >= 10 MeV particles
S5 Extreme

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.***
Satellite operations: satellites may be rendered useless, memory impacts can cause loss of control, may cause serious noise in image data, star-trackers may be unable to locate sources; permanent damage to solar panels possible.
Other systems: complete blackout of HF (high frequency) communications possible through the polar regions, and position errors make navigation operations extremely difficult.

105

S4

Severe

Biological: unavoidable radiation hazard to astronauts on EVA; passengers and crew in high-flying aircraft at high latitudes may be exposed to radiation risk.***
Satellite operations: may experience memory device problems and noise on imaging systems; star-tracker problems may cause orientation problems, and solar panel efficiency can be degraded.
Other systems: blackout of HF radio communications through the polar regions and increased navigation errors over several days are likely.

104

S3

Strong

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.***
Satellite operations: single-event upsets, noise in imaging systems, and slight reduction of efficiency in solar panel are likely.
Other systems: degraded HF radio propagation through the polar regions and navigation position errors likely.

103

S2

Moderate

Biological: passengers and crew in high-flying aircraft at high latitudes may be exposed to elevated radiation risk.***
Satellite operations: infrequent single-event upsets possible.
Other systems: small effects on HF propagation through the polar regions and navigation at polar cap locations possibly affected.

102

S1

Minor

Biological: none.
Satellite operations: none.
Other systems: minor impacts on HF radio in the polar regions.

10