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About Hpo index

 The half-hourly Hp30 and hourly Hp60 were developed at GFZ during in the Horizon 2020-project SWAMI and are described in the publication Yamazaki et al. (2022). These time resolutions are an improvement compared to the three-hourly Kp. Together with their linear versions ap30 and ap60 they are collectively known as the Hpo indices or Hpo index. Here, H refers to the (half-)hourly, p refers to planetary and o refers to open-ended. The latter signifies that Hpo, in contrast to Kp, is not limited to a maximum value of 9. This allows a more nuanced description of the strongest geomagnetic events.

Hpo is provided in near real-time as nowast values. These are preliminary values that are based on all available data and might change ones more data is available for their computation. Hpo goes back to 1995.

The Hpo indices are calculated from the geomagnetic recordings of the following 13 geomagnetic observatories:

geomagnetic Observatory


operating institute



EyrewellEYRGNS ScienceNew Zealand1978
CanberraCNBGeoscience AustraliaAustralia1981
UppsalaUPSGeological Survey of SwedenSweden2004
BrorfeldeBFETechnical University of DenmarkDenmark1984
WingstWNGDeutsches GeoForschungsZentrumGermany1938
NiemegkNGKDeutsches GeoForschungsZentrumGermany1988
LerwickLERBritish Geological SurveyUnited Kingdom1932
EskdalemuirESKBritish Geological SurveyUnited Kingdom1932
HartlandHADBritish Geological SurveyUnited Kingdom1957
OttawaOTTNatural Resources CanadaCanada1969
MeanoookMEANatural Resources CanadaCanada1932
FredricksbergFRDUnited States Geological SurveyUnited States1957
SitkaSITUnited States Geological SurveyUnited States1932

We thank the operating institutes for contributing with their data.