DOI: 10.5880/hpo.0003
title: Geomagnetic Hpo index (V3.0)

description: This data publication includes the half-hourly Hp30 and ap30 indices as well as the hourly Hp60 and ap60 indices, collectively denoted as Hpo. This dataset is based on near real-time geomagnetic observatory data provided by 13 contributing observatories. It is derived and distributed by GFZ German Research Centre for Geosciences. When using the Hpo index, please cite this data publication as well as the accompanying publications Yamazaki et al. (2024) and Yamazaki et al. (2022), which serve as documentation of the Hpo. 
 
The dataset is organised in yearly files, which, for the current year, are updated on a monthly basis. Typically, during the second week of a month, the data for the previous month is appended to the current year's file. The files are in ASCII files and start with header lines marked with # (hash). 
 
The Hpo index was initially developed within the H2020 project SWAMI (grant agreement No 776287) and is produced by Geomagnetic Observatory Niemegk, GFZ German Research Centre for Geosciences. It derives from the same 13 geomagnetic observatories that also contribute to the Kp index (Matzka et al., 2021, https://doi.org/10.5880/Kp.0001). They are listed as contributors to this data publication. 
 
With the introduction of the DOI for the Hpo index (Matzka et al, 2021, https://doi.org/10.5880/Hpo.0001), this DOI landing page and the associated HTTPS server linked to the DOI become the primary archive of Hpo (while the other established index distribution mechanisms at GFZ will be maintained in parallel). With the DOI, the dataset can grow with time, but a change of the data, once published, is not possible. If necessity arises in the future to correct already published values, then the corrected dataset will be published with a new DOI. Older DOIs and data sets will then still be available. For each DOI, an additional versioning mechanism will be available to document changes to the files such as header or format changes, which do not affect the integrity of the data. The DOI https://doi.org/10.5880/Hpo.0003 identifies the current version. A format description and a version history are provided in the data download folder.
description: Version history: 
 
2024-07-10: publication of version 3.0 (https://doi.org/10.5880/Hpo.0003). This version replaces version Hpo.0001 and Hpo.0002. 
 
The algorithm to calculate Hpo was changed to give a better occurrence frequency of index values for Hpo &gt;= 9. Additionally, index values for 1984 to 1995 were added. The change is described in the accompanying publication. 
 
------------------------------------------------------------ 
2022-05-13: Addition of key reference (Yamazaki et al. 2022, https://doi.org/10.1029/2022GL098860) to the landing page, the data files and the format description (metadata update, no new version released) 
 
------------------------------------------------------------ 
2022-03-26: Publication of Version 2.0 (https://doi.org/10.5880/Hpo.0001). This version replaces version Hpo.0001. 
 
The Hpo, like the Kp nowcast, is based on the FMI algorithm (see Matzka et al., 2021, https://doi.org/10.1029/2020SW002641) and goes through a rescaling procedure to be more similar to the definitive Kp values. The data in version Hpo.0001 from 2018 onwards suffered from a slight error in this rescaling algorithm, causing for example somewhat too few Hpo 0 values and somewhat too many Hpo 0.333 values. This error was corrected for version Hpo.0002. The values from 1995 to 2017 are identical for both versions. 
 
------------------------------------------------------------ 
 2021-04-26: Publication of Version 1.0 (https://doi.org/10.5880/Hpo.0001)