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AA Geomagnetic Activity Indices From Two Antipodal Observatories in Australia and England

Published by NOAA National Centers for Environmental Information | National Oceanic and Atmospheric Administration, Department of Commerce | Metadata Last Checked: December 19, 2025 | Last Modified: 1968-01-01T00:00:00.000+00:00
The NOAA National Centers for Environmental Information (formerly National Geophysical Data Center) receives, on a monthly basis, indices that are based on the data from two approximately antipodal observatories in England and Australia. The AA-indices are available from 1868 to present.

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