2.7.1 https://spdx.org/licenses/ SPDX CC-BY-NC-4.0 https://spdx.org/licenses/CC-BY-NC-4.0.html Creative Commons Attribution Non Commercial 4.0 International The Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) license allows users to share, copy, and adapt material in any medium or format, provided they give appropriate credit (attribution) and use the material only for non-commercial purposes. spase://CNES/NumericalData/CDPP-AMDA/Indices/Ground_Based/ground-based-aa Indices - Ground Based - aa aa IAGA-endorsed magnetic activity index https://doi.org/10.25577/9z05-v751 2026-03-19T02:25:06Z 2026-03-19T02:25:06Z Posted by JMW. Index which purpose 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. ISGI website at EOST; aa Citation: Mayaud, P.-N., Menvielle, M., & Chambodut, A. (2023). aa geomagnetic index. EOST. (Dataset). https://doi.org/10.25577/9z05-v751 License: CC BY-NC https://creativecommons.org/licenses/by-nc/4.0/ spase://SMWG/Person/Aude.Chambodut TechnicalContact spase://SMWG/Person/James.M.Weygand MetadataContact aa - IAGA-endorsed geomagnetic indices https://isgi.unistra.fr/indices_aa.php spase://SMWG/Repository/CDPP/AMDA Online Open CDPP/AMDA HAPI Server https://amda.irap.omp.eu/service/hapi ground-based-aa Web Service to this product using the HAPI interface. CSV Thank you for acknowledging the use of AMDA in publications with wording like "Data analysis was performed with the AMDA science analysis system provided by the Centre de Données de la Physique des Plasmas (CDPP) supported by CNRS, CNES, Observatoire de Paris and Université Paul Sabatier, Toulouse". See the Rules of the road at https://amda.cdpp.eu/help/policy.html . Please acknowledge the Data Providers. spase://SMWG/Repository/CDPP/AMDA Online Open CDPP/AMDA Web application https://amda.cdpp.eu Access to Data via CDPP/AMDA Web application. CSV VOTable CDF PNG Thank you for acknowledging the use of AMDA in publications with wording like "Data analysis was performed with the AMDA science analysis system provided by the Centre de Données de la Physique des Plasmas (CDPP) supported by CNRS, CNES, Observatoire de Paris and Université Paul Sabatier, Toulouse". See the Rules of the road at https://amda.cdpp.eu/help/policy.html . Please acknowledge the Data Providers. ISGI spase://CNES/Instrument/CDPP-AMDA/Indices/Ground_Based MagneticField 1975-01-01T00:00:00Z 2025-09-23T21:00:00Z PT3H Earth.NearSurface aa aa nT Magnetic Aa Aa Daily Mean of aa nT Magnetic