aa geomagnetic index


Type: On-going time series of IAGA-endorsed geomagnetic index aa Identifier: doi:10.25577/9z05-v751
Time range: 1868 to now DataCite metadata: [HTML] | [XML]
Institution(s): EOST Data access: here
Archived at: for License:
Citation: Mayaud, P.-N., Menvielle, M., & Chambodut, A. (2023). aa geomagnetic index. EOST. (Dataset).
Description: Purpose of aa index is to measure the amplitude of global geomagnetic activity during 3-hour intervals normalized to geomagnetic latitude ±50°. aa was introduced to monitor geomagnetic activity over the longest possible time period. aa is derived from the K indices measured at two antipodal observatories. The K indices are converted into amplitudes using mid-class amplitudes (K2aK) then averaged with weighting factors that account for slight changes in geomagnetic disturbance intensities between successive Northern and Southern aa-observatories.
Map of geomagnetic observatories used in aa determination:
List of geomagnetic observatories used in aa determination:
Code Name Country Start of use End of use Infos
ABNAbingerUnited Kingdom19261956[infos]
CNBCanberraAustralia1980still used[infos]
GRWGreenwichUnited Kingdom18681925[infos]
HADHartlandUnited Kingdom1957still used[infos]
Data download: https://isgi.unistra.fr/data_download.php
Data plot: https://isgi.unistra.fr/data_plot.php