ap index: The general level of geomagnetic activity over the globe for a given day. A mean, 3-hourly “equivalent amplitude” of magnetic activity based on K index data from several magnetic observatories.
Ap index: A daily index determined from eight ap index values.
Geomagnetic activity: Natural variations in the geomagnetic field classified into quiet, unsettled, active and geomagnetic storm levels.
Geomagnetic storm: A worldwide disturbance of the Earth’s magnetic field, distinct from regular diurnal variations. A storm occurs when:
- Ap = 29 to 50 (minor storm)
- Ap = 50 to 100 (major storm)
- Ap >= 100 (severe storm)
Kp index: The planetary 3-hour-range index Kp is the mean standardized K index from 13 geomagnetic observatories between 44 degrees and 60 degrees northern or southern geomagnetic latitude. The scale is 0 to 9 expressed in thirds of a unit; e.g., 5– is 42/3, 5 is 5 and 5+ is 51/3. This planetary index is designed to measure solar particle radiation by its magnetic effects. The 3-hourly ap (equivalent range) index is derived from the Kp index.
Space Weather Canada (Canadian Space Weather Forecast Centre)
National Resources Canada - Government of Canada
Space Weather Services - Bureau of Meterology
Space Weather Prediction Centre - NOAA - National Weather Service - USA.gov