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EARTH SCIENCE > SUN-EARTH INTERACTIONS > IONOSPHERE/MAGNETOSPHERE DYNAMICS > GEOMAGNETIC INDICES

Definition:
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.


Reference:
NOAA/NGDC Solar-Terrestrial Glossary:
http://www.ngdc.noaa.gov/stp/GLOSSARY/glossary.html