Space Weather Scale for Geomagnetic Storms
Category |
Effect |
Physical measure |
Average Frequency | |
G 5 |
Extreme |
Power systems: grid systems can collapse and transformers experience damage. Spacecraft operations: extensive surface charging, problems with orientation, uplink/downlink, and tracking satellites. Other systems: pipeline currents reach hundreds of amps, HF (high frequency) radio propagation impossible in many areas for one to two days, satellite navigation degraded for days, low-frequency radio navigation out for hours, and the aurora seen as low as the equator. |
Kp = 9 (Kp is a planetary index of magnetic field disturbance — see this page for its definition) |
4 storm events per cycle at this Kp level |
G 4 |
Severe |
Power systems: possible voltage stability problems, portions of grids collapse and protective devices trip. Spacecraft operations: experience surface charging and tracking problems, orientation problems need corrections. Other systems: induced pipeline currents affect preventive measures, HF radio propagation sporadic, satellite navigation degraded for hours, low-frequency radio navigation disrupted, and the aurora seen as low as the tropics. |
Kp = 8, including a 9- |
100 per cycle |
G 3 |
Strong |
Power systems: voltage corrections required, false alarms triggered on protection devices, and high ‘gas-in-oil’ transformer readings likely. Spacecraft operations: surface charging on satellite components, increased drag on satellite, and orientation problems need corrections. Other systems: intermittent satellite navigation and low-frequency radio navigation problems, HF radio intermittent, and the aurora seen as low as mid-latitudes. |
Kp = 7 |
200 per cycle |
G 2 |
Moderate |
Power systems: high-latitude power systems affected. Spacecraft operations: corrective actions are required by ground control; changes in drag affect orbit predictions. Other systems: HF radio propagation fades at higher latitudes, and the aurora seen as low as 50 degrees. |
Kp = 6 |
600 per cycle |
G 1 |
Minor |
Power systems:weak power grid fluctuations. Spacecraft operations: minor impact on satellite operations. Other systems: the aurora seen at high latitudes (60 degrees); migratory animals begin to be affected. |
Kp = 5 |
1700 per cycle |
Table from National Oceanic and Atmospheric Administration
