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: Geomagnetic jerks (abrupt changes of secular variation) and decadal variations of the length of day both originate in core flow; jerks often coincide with extrema of the length-of-day variation (Holme & de Viron, 2013; Mandea et al., 2010).

Events used

composite change in the jerk year: 0.019 ms/yr

Period analysed

1962 → 2024

computed on Oct 23, 2026 · engine v1.0

Analysed series and events

Show the data as a table

Yearly mean; events in the years 1969, 1978, 1991, 2003, 2014.

Superposed epochs

Show the data as a table

Mean anomaly around the 5 events (1969, 1978, 1991, 2003, 2014), relative to the mean of the years before each event; dashed lines are the 5th and 95th percentiles of composites built on randomly drawn events (Monte-Carlo).

Superposed epochs of the yearly change

Show the data as a table

Mean anomaly around the 5 events (), relative to the mean of the years before each event; dashed lines are the 5th and 95th percentiles of composites built on randomly drawn events (Monte-Carlo).

Aligned series (CSV)

Method and sources

Yearly mean of the length of day (IERS C04, 1962–) and its year-to-year change, superposed around the jerk years listed in the atlas context data (literature values with DOIs), anomalies relative to the six preceding years; Monte-Carlo band over 2000 draws.

Computation parameters

{
    "sea": {
        "after": 6,
        "draws": 2000,
        "before": 6
    },
    "change": "LOD(year) − LOD(year − 1)",
    "series": "yearly mean of daily LOD, last incomplete year dropped"
}

Inputs : iers.lod.daily (23,136 pts, run #66)

Reading this result

Only five events: the Monte-Carlo band is wide and no formal test is conclusive; the page illustrates a coincidence discussed in the literature, not a demonstration. 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

IERS EOP 20 C04 daily Earth orientation since 1962: IERS Earth Orientation Centre, EOP 20 C04 (IAU2000A) combined series, 1962–; Bizouard, C., et al. (2019), J. Geod. 93, 621–633. · doi:10.1007/s00190-018-1186-3 · source page ↗
Licence : IERS data, free use with citation (Bizouard et al., 2019) · retrieved on Oct 23, 2026 · SHA-256 395e94687b8a…
Holme et al. (2013): Holme, R., & de Viron, O. (2013). Characterization and implications of intradecadal variations in length of day. Nature, 499, 202–204. · doi:10.1038/nature12282
Licence : Published literature; cited
Mandea et al. (2010): Mandea, M., Holme, R., Pais, A., Pinheiro, K., Jackson, A., & Verbanac, G. (2010). Geomagnetic jerks: rapid core field variations and core dynamics. Space Science Reviews, 155, 147–175. · doi:10.1007/s11214-010-9663-x
Licence : Published literature; cited

Geomagnetic jerks and length of day Two signatures of the core

What is linked, what is not