| Term: | Ap index |
| Definition: |
Formally determined from the eight daily ap indices. However, for daily operational uses, NOAA/SWPC estimates the value of the Ap index by measuring the geomagnetic field in near-real time at several magnetometer stations around the world. The real-time station indices are used to estimate the official Kp and Ap based on historical data. The value of this estimated Ap index is reported in NOAA daily and weekly summaries of geophysical activity. |