The field measured on the ground
Twelve observatories, from the auroral zone to the equator, record the three components of the magnetic field every minute. Marker colour and height follow the strongest hourly change of the horizontal field over the last 24 hours.
- < 3 nT/min
- 3–10
- 10–30
- 30–100
- ≥ 100
Positions of the selected INTERMAGNET observatories; dB/dt: hourly maximum of the one-minute change of the horizontal field, in nT/min.
| IAGA | Observatory | Latitude | Institute | Data | dB/dt 24 h (nT/min) | Hourly record (nT/min) | Declination (′/yr) | F (nT/yr) |
|---|---|---|---|---|---|---|---|---|
| ABK | Abisko, Sweden | 68.4° | Sveriges geologiska undersokning | quasi-definitive | 43.2 (2024-07-04) | 607 2024-05-12 | — | — |
| CMO | College, USA | 64.9° | USGS | Definitive | 61.4 (2024-07-04) | 1,066 2024-03-24 | — | — |
| NAQ | Narsarsuaq | 61.2° | DTU | quasi-definitive | 21.2 (2024-07-04) | 528 2024-05-11 | — | — |
| LER | Lerwick | 60.1° | British Geological Survey (BGS) | quasi-definitive | 8.3 (2024-07-04) | 451 2024-05-11 | — | — |
| NGK | Niemegk, Germany | 52.1° | GFZ | Definitive | 7.2 (2024-07-04) | 391 2024-05-10 | — | — |
| CLF | Chambon la Foret, France | 48.0° | IPGP | Definitive | 6.3 (2024-07-04) | 107 2024-05-10 | — | — |
| BOU | Boulder, USA | 40.1° | USGS | Definitive | 6.0 (2024-07-04) | 253 2024-05-10 | — | — |
| KAK | Kakioka, Japan | 36.2° | JMA | Definitive | 2.4 (2024-07-04) | 85 2024-05-10 | — | — |
| TAM | Tamanrasset, Algeria | 22.8° | IPGP | Definitive | 4.4 (2024-07-04) | 93 2024-05-10 | — | — |
| HON | Honolulu, USA | 21.3° | USGS | Definitive | 1.8 (2024-07-04) | 87 2024-05-10 | — | — |
| HER | Hermanus, South Africa | -34.4° | SSS | Definitive | 1.5 (2024-07-04) | 41 2024-03-24 | — | — |
| CNB | Canberra, Australia | -35.3° | GA | Definitive | 3.8 (2024-07-04) | 165 2024-05-10 | — | — |
Show the data as a table
Show the data as a table
Show the data as a table
- ABK: 5 storms, median peak 159.2 nT/min at -4 h, against 6.2 nT/min over all hours (× 26)
- LER: 5 storms, median peak 58.6 nT/min at -2 h, against 1.8 nT/min over all hours (× 33)
- CLF: 5 storms, median peak 17.3 nT/min at 0 h, against 1.3 nT/min over all hours (× 13)
- HON: 5 storms, median peak 9.6 nT/min at -1 h, against 0.6 nT/min over all hours (× 16)
Storms used
2024-03-03 (Dst -112 nT) · 2024-03-24 (Dst -128 nT) · 2024-04-19 (Dst -117 nT) · 2024-05-11 (Dst -406 nT) · 2024-06-28 (Dst -107 nT)
Show the data as a table
One-minute data from INTERMAGNET observatories (IAGA-2002 format) read at the GIN of the British Geological Survey, in the “adjusted or reported” state: recent months are variation data, provisional, replaced by the definitive data when the institute releases them. They are reduced on import to hourly means of X (geographic north), Y (east), Z (vertical, downward) and F (total field, measured independently), and to the hourly maximum of dB/dt = √(ΔX² + ΔY²) between consecutive minutes, the quantity that drives the currents induced in power grids and pipelines (Pulkkinen et al., 2017). An hour is kept only with at least 45 valid minutes.
Internal and external field. More than 90% of the measured field comes from the core and changes slowly: this is the secular variation, modelled every five years by the IGRF (Alken et al., 2021), which moves the magnetic pole of the atlas. The rest, highly variable, comes from currents in the ionosphere and magnetosphere driven by the solar wind: these are the storms, summarised by Kp and Hp60 (Matzka et al., 2021; Yamazaki et al., 2022). Neither has anything to do with the rotation pole, which geodesy tracks separately.
Twelve observatories do not make a map: dB/dt changes a lot over a few hundred kilometres with magnetic latitude and ground conductivity, and hourly values smooth out peaks lasting seconds. The site is not a warning service (see NOAA SWPC or the national space weather services).
Variation data sometimes contain instrumental jumps, corrected only in the definitive data. Secular variation over less than three years remains sensitive to the solar cycle and storms; it agrees in order of magnitude with the pole drift of the atlas.
- INTERMAGNET one-minute magnetic observatory data (BGS Edinburgh GIN)
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The results presented here rely on data collected at magnetic observatories. We thank the national institutes that support them and INTERMAGNET for promoting high standards of magnetic observatory practice (www.intermagnet.org). Observatories: Abisko (SGU), College (USGS), Narsarsuaq (DTU Space), Lerwick (BGS), Chambon-la-Forêt (IPGP), Niemegk (GFZ), Boulder (USGS), Kakioka (JMA), Tamanrasset (CRAAG), Honolulu (USGS), Hermanus (SANSA), Canberra (Geoscience Australia).
· source page ↗
Licence : CC BY-NC 4.0 (INTERMAGNET conditions of use): non-commercial use, acknowledgement of INTERMAGNET and of the observatory institutes · retrieved on Oct 25, 2026 · SHA-256 38494943bfd9… - Geomagnetic Kp and ap indices (GFZ Helmholtz Centre for Geosciences)
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Matzka, J., Stolle, C., Yamazaki, Y., Bronkalla, O. and Morschhauser, A. (2021). The geomagnetic Kp index and derived indices of geomagnetic activity. Space Weather, 19, e2020SW002641. Data: Matzka, J., Bronkalla, O., Tornow, K., Elger, K. and Stolle, C. (2021). Geomagnetic Kp index. V. 1.0. GFZ Data Services.
· doi:10.5880/Kp.0001 · source page ↗
Licence : CC BY 4.0; cite Matzka et al. (2021) · retrieved on Oct 25, 2026 · SHA-256 2961750edc66… - Geomagnetic Hp60 and ap60 indices (GFZ)
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Yamazaki, Y., Matzka, J., Stolle, C., Kervalishvili, G., Rauberg, J., Bronkalla, O., et al. (2022). Geomagnetic activity index Hpo. Geophysical Research Letters, 49, e2022GL098860. Version 3.0: Yamazaki, Y., Matzka, J., da Silva, M.V., Kervalishvili, G., Korte, M. and Rauberg, J. (2024), ESS Open Archive. Data: Matzka, J., Bronkalla, O., da Silva, M.V., Kervalishvili, G., Rauberg, J., Korte, M. and Yamazaki, Y. (2024). Geomagnetic Hpo index. V. 3.0. GFZ Data Services.
· doi:10.5880/Hpo.0003 · source page ↗
Licence : CC BY 4.0; cite Yamazaki et al. (2022) · retrieved on Oct 25, 2026 · SHA-256 e0d990f841cf… - Matzka et al. (2021)
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Matzka, J., Stolle, C., Yamazaki, Y., Bronkalla, O., & Morschhauser, A. (2021). The geomagnetic Kp index and derived indices of geomagnetic activity. Space Weather, 19(5), e2020SW002641.
· doi:10.1029/2020SW002641
Licence : Published literature; cited - Yamazaki et al. (2022)
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Yamazaki, Y., Matzka, J., Stolle, C., Kervalishvili, G., Rauberg, J., Bronkalla, O., et al. (2022). Geomagnetic activity index Hpo. Geophysical Research Letters, 49(10), e2022GL098860.
· doi:10.1029/2022GL098860
Licence : Published literature; cited - Pulkkinen et al. (2017)
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Pulkkinen, A., Bernabeu, E., Thomson, A., Viljanen, A., Pirjola, R., Boteler, D., et al. (2017). Geomagnetically induced currents: Science, engineering, and applications readiness. Space Weather, 15(7), 828–856.
· doi:10.1002/2016SW001501
Licence : Published literature; cited - Alken et al. (2021)
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Alken, P., Thébault, E., Beggan, C. D., Amit, H., Aubert, J., Baerenzung, J., et al. (2021). International Geomagnetic Reference Field: the thirteenth generation. Earth, Planets and Space, 73, 49.
· doi:10.1186/s40623-020-01288-x
Licence : Published literature; cited