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
28
Clear links
21
Causation demonstrated
0
Arc width from |r| of the stored result; several tests between the same phenomena are drawn as stacked arcs.
Hypothesis tested: The shock and magnetic cloud of an Earth-directed CME sweep galactic cosmic rays away: the ground count rate drops by a few percent in less than a day and recovers within about a week (Forbush decrease; Cane, 2000).
Events used
389
minimum composite anomaly -1.11 %
Days outside chance
9
out of 9 days tested after the event
Verdict
Clear effect
clear effect: two consecutive days outside the 5–95 % band
Control: composite minimum (nT)
-0.3
285 days of limb CMEs, 6 day(s) outside the band
Period analysed
1996-01-01 → 2026-10-25
computed on Oct 25, 2026 · engine v1.0
Superposed epochs
Show the data as a table
Control group: fast CMEs seen at the limb
Show the data as a table
Method and sources
Days with at least one full-halo CME of 1000 km/s or more in the SOHO/LASCO (CDAW) catalogue since 1996. Response: daily corrected count rate of the Oulu monitor in percent of its mean since 1996, departure from the mean of the five days before the event. Monte-Carlo band (5–95 %) from 1000 sets of random dates; a result is retained when at least two consecutive days leave the band. Control: fast limb CMEs (narrower than 120°), not heading towards the Earth.
Computation parameters
{
"draws": 1000,
"events": "days with a full-halo CME ≥ 1000 km/s (SOHO/LASCO CDAW)",
"control": "days with a non-halo CME ≥ 1000 km/s narrower than 120° (limb events), halo days removed",
"response": "daily corrected count rate of the Oulu neutron monitor, % of its mean since 1996",
"after_days": 8,
"before_days": 5,
"significance": "at least two consecutive days outside the Monte-Carlo 5–95 % band"
}Inputs : cdaw.cme.fast_halo.yearly (31 pts, run #10) · oulu.nm.daily (22,811 pts, run #3730)
Reading this result
The mean drop of about 1 % is smaller than typical Forbush decreases (2 to 10 %): many halos come from the far side of the Sun and miss the Earth, which dilutes the average. The limb-CME control drops too, three times less: those CMEs occur in the same active periods as the halos, often a few days apart, so the control is not independent. The difference between the two curves remains the most telling measure. 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
- SOHO/LASCO CME catalogue (CDAW Data Center)
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Yashiro, S., Gopalswamy, N., et al. (2004). A catalog of white light coronal mass ejections observed by the SOHO spacecraft. JGR 109, A07105; Gopalswamy, N., et al. (2009), Earth Moon Planets 104, 295. The CME catalog is generated and maintained at the CDAW Data Center by NASA and The Catholic University of America in cooperation with the Naval Research Laboratory. SOHO is a project of international cooperation between ESA and NASA.
· doi:10.1029/2003JA010282 · source page ↗
Licence : NASA, public domain; acknowledgement requested (CDAW, SOHO is an ESA/NASA project) · retrieved on Oct 23, 2026 · SHA-256 7f74bca5d28a… - Oulu neutron monitor, daily corrected count rate (Sodankylä Geophysical Observatory)
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Oulu neutron monitor data, cosmicrays.oulu.fi, Sodankylä Geophysical Observatory of the University of Oulu (6NM64 standard neutron monitor at 65.05° N, 25.47° E, geomagnetic cutoff rigidity ≈ 0.8 GV).
· source page ↗
Licence : Research, educational and public non-commercial use; acknowledge cosmicrays.oulu.fi and the Sodankylä Geophysical Observatory (commercial use: contact the station manager) · retrieved on Oct 25, 2026 · SHA-256 fc2f77ecf31e… - Cane (2000)
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Cane, H. V. (2000). Coronal mass ejections and Forbush decreases. Space Science Reviews, 93, 55–77.
· doi:10.1023/A:1026532125747
Licence : Published literature; cited