Hall of storms · #8 / 10
September 18–19, 1941
Peak Kp
Kp 9.0
G5 — top storm class
Peak moment
03:00 UTC
September 19, 1941
Duration
2 days
September 18–19, 1941
At the ceiling
9.0 ×1
1 intervals at Kp 9.0
The storm, three hours at a time
How long did it hold, and when did it peak?
27 hours at G4 or above · 48 at G1 or above
| Time (UTC) | Kp | Source |
|---|---|---|
| Sep 17 · 00:00 UTC | 2.7 | measured |
| Sep 17 · 03:00 UTC | 2.0 | measured |
| Sep 17 · 06:00 UTC | 3.0 | measured |
| Sep 17 · 09:00 UTC | 1.3 | measured |
| Sep 17 · 12:00 UTC | 2.7 | measured |
| Sep 17 · 15:00 UTC | 3.0 | measured |
| Sep 17 · 18:00 UTC | 2.3 | measured |
| Sep 17 · 21:00 UTC | 1.0 | measured |
| Sep 18 · 00:00 UTC | 2.0 | measured |
| Sep 18 · 03:00 UTC | 6.7 | measured |
| Sep 18 · 06:00 UTC | 8.3 | measured |
| Sep 18 · 09:00 UTC | 8.7 | measured |
| Sep 18 · 12:00 UTC | 8.7 | measured |
| Sep 18 · 15:00 UTC | 8.7 | measured |
| Sep 18 · 18:00 UTC | 8.7 | measured |
| Sep 18 · 21:00 UTC | 8.7 | measured |
| Sep 19 · 00:00 UTC | 8.7 | measured |
| Sep 19 · 03:00 UTC | 9.0 | measured |
| Sep 19 · 06:00 UTC | 8.7 | measured |
| Sep 19 · 09:00 UTC | 7.3 | measured |
| Sep 19 · 12:00 UTC | 4.0 | measured |
| Sep 19 · 15:00 UTC | 5.0 | measured |
| Sep 19 · 18:00 UTC | 7.3 | measured |
| Sep 19 · 21:00 UTC | 4.0 | measured |
| Sep 20 · 00:00 UTC | 5.3 | measured |
| Sep 20 · 03:00 UTC | 4.3 | measured |
| Sep 20 · 06:00 UTC | 4.0 | measured |
| Sep 20 · 09:00 UTC | 6.3 | measured |
| Sep 20 · 12:00 UTC | 5.3 | measured |
| Sep 20 · 15:00 UTC | 3.0 | measured |
| Sep 20 · 18:00 UTC | 2.0 | measured |
| Sep 20 · 21:00 UTC | 1.3 | measured |
under 3 · quiet3 to G1 · activeG1–G4 · stormG5 · extreme
Each bar is a three-hour UTC slot · lines at each 00 UTC · shaded days are the storm itself · GFZ definitive Kp.
What it reached
North America & Europe — aurora over wartime blackouts
Open in the archive
September 1941 — the three-hourly Kp values, day by day
From the ground
The Night It Broke — one substorm at Skaftafell, minute by minute
Replay
Replay this night’s sky in the simulator — from the archive’s eight Kp values