FAQ for ISO 19115 and 19115-2 Back to Collection NOAA/NESDIS/NGDC/STP/Indices

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