The indicative of solar flare importance given by the sum of the following five components

1. Importance of ionizing radiation as indicated by time- associated Short Wave Fade or Sudden Ionospheric Disturbance; (Scale 0-3)
2. Importance of H-Alpha flare; (Scale 0-3)
3. Magnitude of 10cm flux; (Characteristic of log of flux in units of 10^-22Watt/m²/Hz)
4. Dynamic spectrum; (Type II = 1, Continuum = 2, Type IV with duration > 10 minutes = 3)
5. Magnitude of 200MHz flux; (Characteristic of log of flux in units of 10^-22Watt/m²/Hz)
   

ON-LINE GLOSSARY OF SOLAR-TERRESTRIAL TERMS of National Geophysics Data Center