Space Weather Alerts

Active alerts, warnings, and NOAA space weather scales

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NOAA Space Weather Scales

Geomagnetic (G-Scale)

Solar (S-Scale)

Radio (R-Scale)

Understanding Space Weather Scales

NOAA uses three scales to categorize space weather events: Geomagnetic (G), Solar (S), and Radio (R). Each scale ranges from 1 (minor) to 5 (extreme).

G-Scale (Geomagnetic)

Measures geomagnetic storm intensity based on Kp Index and DST values:

  • G1 (Minor): Kp 5, DST -50 nT - Minor aurora at high latitudes
  • G2 (Moderate): Kp 6, DST -100 nT - Aurora visible at mid-latitudes
  • G3 (Strong): Kp 7, DST -200 nT - Aurora visible at lower latitudes
  • G4 (Severe): Kp 8, DST -300 nT - Aurora visible at very low latitudes
  • G5 (Extreme): Kp 9, DST -500 nT - Aurora visible near equator

S-Scale (Solar Radiation)

Measures solar radiation storm intensity. Higher levels can affect satellites and high-altitude aircraft, but don't directly impact aurora viewing from the ground.

R-Scale (Radio Blackout)

Measures radio blackout intensity caused by X-ray flares. Higher levels can disrupt HF radio communications but don't directly affect aurora visibility.