Correspondences

What is linked, what is not

Each arc joins two phenomena tested on this site. Green and animated: clear link (correlation significant at 5 % after correcting for autocorrelation, or a response outside chance in an event study). Grey: inconclusive test. A statistical link alone does not establish causation.

Clear link
Inconclusive

Hypotheses tested

Clear links

correlation p < 0.05 or epochs outside chance

Causation demonstrated

a correlation demonstrates none

Arc width from |r| of the stored result; several tests between the same phenomena are drawn as stacked arcs.

Hypothesis tested: A geomagnetic storm intensifies the currents of the ionosphere and magnetosphere: the ground field changes fast, mostly under the auroral oval, and induces currents in power grids and pipelines (Pulkkinen et al., 2017).

Pearson correlation r (lag 0 days)

0.77

95% interval [0.69; 0.83] (block bootstrap)

Aligned points

186

effective n ≈ 140 (autocorrelation)

p-value

0.00000

two-sided, Fisher z transform, effective n

r with Chambon-la-Forêt

0.80

186 days; mid-latitude (France)

Abisko / Chambon-la-Forêt ratio

median of the daily maxima, storm days (Hp60 ≥ 6)

Period analysed

2024-01-01 → 2024-07-04

computed on Oct 25, 2026 · engine v1.0

Aligned series (standard deviations, after preprocessing)

Show the data as a table

Both series are drawn in standard-deviation units (z) after removing the seasonal cycle and slow variations, to compare their fluctuations; original values are in the table and the CSV export.

Correlation by lag (days)

Show the data as a table

Pearson coefficient for each lag; a positive lag means the second series follows the first. The table gives n, effective n and p for each lag.

Aligned series (CSV)

Method and sources

Daily maximum of the Hp60 index (GFZ, hourly); daily maximum of the hourly |dB/dt| at Abisko (Sweden, auroral zone) and Chambon-la-Forêt (France), computed by the observatory from one-minute INTERMAGNET data, artefacts removed. Base-10 logarithm of both (very skewed distributions). Lags of −3 to +3 days, fixed at zero; Pearson, effective size, 7-day block bootstrap.

Computation parameters

{
    "x": "log10 of the daily maximum of Hp60 (GFZ)",
    "y": "log10 of the daily maximum of hourly |dB/dt| at Abisko (INTERMAGNET, artefacts removed)",
    "contrast": "same with Chambon-la-Forêt",
    "bootstrap": {
        "seed": 20261023,
        "block": 7,
        "draws": 1000
    },
    "lags_days": "−3…+3, fixed at 0",
    "storm_ratio": "median Abisko/Chambon-la-Forêt ratio of the daily maxima on days with Hp60 ≥ 6"
}

Inputs : gfz.hp60.hourly (366,528 pts, run #3698) · intermagnet.abk.dbdt.hourly (4,464 pts, run #3717) · intermagnet.clf.dbdt.hourly (4,463 pts, run #3717)

Reading this result

This is a positive control: the link is expected and very strong, and it validates the processing chain (indices, observatory data, artefact filtering). The planetary index does not tell everything: for the same storm, the ground variation depends on latitude, local time and ground conductivity. The period covers only the maximum of cycle 25. Correlation is not causation: common factors (seasons, cycles, trends) or coincidence can produce it. The p-values account for autocorrelation (effective n) but not for preprocessing choices; the confidence interval comes from a block bootstrap. The limits of the source data apply.

SOURCES OF THIS PAGE

Geomagnetic Hp60 and ap60 indices (GFZ): 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…
INTERMAGNET one-minute magnetic observatory data (BGS Edinburgh GIN): 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…
Pulkkinen et al. (2017): Pulkkinen, A., Bernabeu, E., Thomson, A., Viljanen, A., Pirjola, R., 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

Storms and the ground magnetic field Magnetic storms shake the ground field, ten times more under the aurora

What is linked, what is not