NOAA Space Weather Scales

A shorthand classification scheme developed to convey to the general public the complex and often confusing levels of disturbances in the solar-terrestrial environment.  Three typical events are represented as:  Geomagnetic Storms (G), Solar Radiation Storms (S), and Radio Blackouts (R).  A numerical qualifier is added to the event type to indicate the severity of the disturbance.  These qualifiers are defined as follows:
1
Minor
2
Moderate
3
Strong
4
Severe
5
Extreme
See Appendix A for complete descriptions of normal terrestrial system effects, threshold levels, and event frequency of occurrence.