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Geomagnetic activity in September 1939
Mean Ap13.2No. 484 of 1138
G1+ days7
G3+ days1
Max Ap5517 Sep 1939
Daily Ap
Daily max Kp
| Date | Max Kp | Ap | Level |
|---|---|---|---|
| 2 Sep 1939 | 5- | 10 | G1 |
| 3 Sep 1939 | 6o | 40 | G2 |
| 9 Sep 1939 | 5+ | 26 | G1 |
| 17 Sep 1939 | 7o | 55 | G3 |
| 19 Sep 1939 | 5+ | 33 | G1 |
| 20 Sep 1939 | 5+ | 33 | G1 |
| 26 Sep 1939 | 5+ | 24 | G1 |
Same month a year earlier
| Month | Mean Ap | G1+ | G3+ |
|---|---|---|---|
| September 1938 | 16.8 | 7 | 4 |
| September 1939 | 13.2 | 7 | 1 |
Dates and time slots are UTC. Kp is the 3-hourly planetary geomagnetic index (0–9); Ap is the daily average disturbance. G1–G5 follow the NOAA storm scale (Kp 5- and above counted as G1). Aurora visibility also depends on weather and location. The latest values are preliminary.
About this page
Mean Ap 13.2 in September 1939, No. 484 of 1138 months since 1932; 7 days reached G1 or higher.