Value chain · CLM-0118
Low confidence
The evidence behind this statement is thin, indirect or second-hand. Read it as a lead to check, not as a settled finding.
In plain terms
Storms big enough to disturb the ionosphere over the UK happen on roughly 12 to 18 days a year on average, mostly around solar maximum. Which figure is right is not yet known.
The claim as recorded
Geomagnetic storms of NOAA class G3 and above occur on about 130, 60 and 4 days per 11-year solar cycle for G3, G4 and G5 respectively, about 17.6 days per year in total averaged across a cycle if NOAA's counts are exclusive to each class, or about 11.8 days per year if each count includes the higher classes (130 days per cycle at G3 and above), concentrated near solar maximum; WHICH READING IS RIGHT IS UNVERIFIED, because NOAA's table does not say, and NOAA's aurora-visibility latitude thresholds of 50, 45 and 40 degrees north for G3, G4 and G5 place the disturbed zone at or below the UK's approximate 54 degrees north magnetic latitude for all three classes.
Evidence behind this: T3: an agency's published scale and table, not a peer-reviewed measurement.
Scope and limits
THE ASSUMPTION ABOVE IS WEAK AND IS THE REASON CONFIDENCE IS LOW. Optical aurora and radio absorption are produced by different electron energy populations, so the visibility boundary is a proxy and not a measurement of where absorption reaches. The occurrence figures are solid; the latitude transfer is not. Combined with CLM-0117, this gives a duty cycle without a usable magnitude, which is not yet an availability estimate.
What it assumes
that the aurora-visibility boundary is a usable proxy for the absorption-zone boundary
Where it comes from
for the occurrence table and the latitude thresholds; table read at the NOAA page 2026-10-03 (PDF p.1): G3 "200 per cycle (130 days per cycle)", G4 "100 per cycle (60 days per cycle)", G5 "4 per cycle (4 days per cycle)"; aurora typically at 50, 45 and 40 degrees geomagnetic latitude for G3, G4 and G5. Whether the counts are exclusive or cumulative is not stated; see CLM-1381. UK magnetic latitude of about 54 N derived from the IGRF-14 data in SRC-122.
Related records
- Answers question
- QST-009 not published in this release
Cite this
energyaperture.com/c/clm-0118
CLM-0118, Energy Aperture, as of 2026-09.
Connected records
Other published records linked to this one. A list, not a judgement.
- Also from SRC-122
- CLM-0400Millstone Hill sits at almost exactly the UK's magnetic dip angle, and the UK's modelled density range fits entirely inside what Millstone...
- Also from SRC-135
- CLM-1380NOAA's storm levels G1 to G5 correspond to the Kp disturbance index reaching 5, 6, 7, 8 and 9.CLM-1381NOAA's own table confirms the storm-day counts the register was using: about 130 strong, 60 severe and 4 extreme storm days in an average...