am geomagnetic index


Type: On-going time series of IAGA-endorsed geomagnetic index am Identifier: doi:10.25577/et43-6h78
Time range: 1959 to now DataCite metadata: [HTML] | [XML]
Institution(s): EOST Data access: here
Archived at: for License:
Citation: Mayaud, P.-N., Berthelier, A., Menvielle, M., & Chambodut, A. (2023). am geomagnetic index. EOST. (Dataset). doi:10.25577/et43-6h78
Description: The purpose of am geomagnetic indices is to provide a characterization of global geomagnetic activity using a large set of stations representing all longitudes and possible hemispheric discrepancies. The stations are situated close to 50° corrected geomagnetic latitude (in the subauroral zones), and are gathered into groups, each corresponding to a longitude sector. There are 5 such groups in the Northern hemisphere, and 4 in the Southern one. In each longitude sector, the K scaled for each station, are averaged, and the result is converted into amplitude using mid-class amplitudes for L9 = 500 nT (L9 being the K=9 lower limit; conversion table K2aK). The weighted average of the so-obtained amplitudes give rise to the hemispheric indices an (North) and as (South), the weighting factors accounting for the differences in the longitude sector extents in each hemisphere. The planetary index am is equal to (an + as) / 2.
Map of geomagnetic observatories used in am determination:
List of geomagnetic observatories used in am determination:
Code Name Country Start of use End of use Infos
AIAArgentine Islands (Akademik Vernadsky Base)Antarctica (Ukraine)1959still used[infos]
AMLAmberleyNew Zealand19591977[infos]
AMSMartin De Vivies-Amsterdam IslandFrench Southern and Antarctic Lands (France)1986still used[infos]
ARSArtiRussia1981still used[infos]
CLFChambon La ForetFrance1995still used[infos]
CNBCanberraAustralia1979still used[infos]
CZTPort AlfredFrench Southern and Antarctic Lands (France)1969still used[infos]
EYREyrewellNew Zealand1978still used[infos]
FRDFredericksburgUnited States of America1959still used[infos]
GNGGinginAustralia2013still used[infos]
HADHartlandUnited Kingdom1959still used[infos]
HERHermanusSouth Africa1955still used[infos]
IRTIrkutskRussia1998still used[infos]
KEPKing Edward PointUnited Kingdom2018still used[infos]
LAULauderNew Zealand19791985[infos]
MGDMagadanRussia1967still used[infos]
MMBMemambetsuJapan1959still used[infos]
NEWNewportUnited States of America1975still used[infos]
NGKNiemegkGermany1959still used[infos]
NVSNovosibirskRussia2000still used[infos]
OTTOttawaCanada1975still used[infos]
PAFPort-Aux-FrancaisFrench Southern and Antarctic Lands (France)1959still used[infos]
PETParatunka/PetropavlovskRussia1969still used[infos]
PODBor (Podkamennaya Tunguska)Russia19731994[infos]
PSTPort StanleyFalkland Islands (United Kingdom)2003still used[infos]
SGESouth GeorgiaUnited Kingdom19751982[infos]
SVDVysokaya DubravaRussia19591980[infos]
TRWTrelewArgentina1973still used[infos]
TUCTucsonUnited States of America1959still used[infos]
VICVictoriaCanada1959still used[infos]
Data download:
Data plot: