{"HAPI":"3.3.1","status":{"code":1200,"message":"OK"},"startDate":"1932-01-01T01:30:00Z","stopDate":"2026-09-14T19:00:00Z","cadence":"PT3H","timeStampLocation":"center","modificationDate":"2026-09-14T10:35:02Z","title":"Kp and ap Indices (Best Available, 3-hour)","description":"Planetary geomagnetic 3-hourly indices Kp and ap: Kp, introduced by Bartels (1949) and endorsed by IAGA, is derived from K-values recorded at 13 geomagnetic observatories; ap is the equivalent planetary amplitude (unit: 2 nT) derived from Kp. Kp is encoded as a decimal where the plus/minus thirds map to fractional parts .3 and .7 (e.g. 3−=2.7, 3o=3.0, 3+=3.3). Produced by GFZ Potsdam, redistributed by WDC for Geomagnetism, Kyoto. Best Available version: highest processing level per period (currently definitive only). Timestamps are bin centers of each 3-hour interval (01:30, 04:30, ... 22:30 UT; timeStampLocation=center).","resourceID":"doi:10.5880/Kp.0001","datasetCitation":"Matzka, J., Stolle, C., Yamazaki, Y., Bronkalla, O., & Morschhauser, A. (2021). The Geomagnetic Kp Index and Derived Indices of Geomagnetic Activity. Space Weather, 19, e2020SW002641. doi:10.1029/2020SW002641. Kp index data: Matzka, J., Bronkalla, O., Tornow, K., Elger, K., & Stolle, C. (2021), Geomagnetic Kp index, V. 1.0, GFZ Data Services, doi:10.5880/Kp.0001. Redistributed via WDC for Geomagnetism, Kyoto.","licenseURL":"https://creativecommons.org/licenses/by/4.0/","parameters":[{"name":"Time","type":"isotime","units":"UTC","fill":null,"length":24,"label":"Time"},{"name":"kpValue","type":"double","units":null,"fill":"99.9","label":"Kp","description":"Planetary K index (0-9 scale), 3-hourly. Plus/minus thirds encoded as decimals .3 and .7 (3−=2.7, 3o=3.0, 3+=3.3)."},{"name":"apValue","type":"integer","units":null,"fill":"999","label":"ap","description":"Equivalent planetary amplitude (unit: 2 nT), 3-hourly, derived from Kp."},{"name":"versionCode","type":"integer","units":null,"fill":null,"label":"Version Code","description":"Processing status code Mm (major*10+minor). Currently a single definitive version (versionCode 20)."}]}