G1 (Minor) Geomagnetic Storm of April 22, 1951
A G1 (minor) geomagnetic storm began April 22, 1951, reached Kp 5+ and lasted 30 hours, with a daily Ap as high as 42; at that Kp the aurora may be seen from about 58 degrees geomagnetic latitude.
The Kp through the storm
Began Apr 22, 00:00 UTC, peaked in the block from Apr 22, 00:00 UTC, ended Apr 23, 06:00 UTC.
The storm
- Peak Kp
- 5+ (5.33)
- NOAA level
- G1 Minor
- Duration
- 30 hours
- Highest daily Ap
- 42
- Highest 3-hour ap
- 56
- Rank since 1932
- 2,153 of 4,139
How far south the aurora could have been seen
At Kp 5+ NOAA’s scales put the aurora’s reach at about 58 degrees geomagnetic latitude: 50°N in the central US, 49°N in the eastern US, 53°N in the western US and 59°N in northern Europe.
NOAA says a G1 storm’s aurora commonly visible at high latitudes: northern Michigan and Maine.
US cities within reach, the southernmost first
- Anchorage, AK 61.9° geomag.
1 US cities of 150,000 people or more sit at or poleward of that line. Low on the northern horizon under a dark, clear sky; not a record of sightings.
Day by day
The daily Ap is the mean of the day’s eight three-hour ap values.
| UT day | Daily Ap | Highest Kp that day |
|---|---|---|
| April 22, 1951 | 42 | 5+ |
| April 23, 1951 | 16 | 5 |
More
The storm before, Apr 20The storm after, Apr 24Every storm of 1951The strongest on recordThis day in weather historyTonight’s aurora forecast
Sources
Kp and ap from GFZ Helmholtz Centre for Geosciences, Geomagnetic Observatory Niemegk, licensed CC BY 4.0: Matzka, J., Stolle, C., Yamazaki, Y., Bronkalla, O. and Morschhauser, A., 2021, The geomagnetic Kp index and derived indices of geomagnetic activity, Space Weather, doi:10.1029/2020SW002641; data doi:10.5880/Kp.0001. Storms, levels and aurora reach worked out by WeatherOverTime from those values and NOAA’s space weather scales. Definitive through August 31, 2026; later values are preliminary. Rebuilt 2026-09-24.