Geomagnetic indices are an indicator of geomagntic activity caused by solar events. Typical geomagntic indices are: a, A, Ap, Dst, K, and Kp. The A-index,
for example, is a daily average composed of 3-hour data points. Geomagnetic indices can be used in conjunction with solar"wind" data to predict the onset and intensity of geomagnetic storms.
