G1 (Minor) Geomagnetic Storm of January 11, 1955
A G1 (minor) geomagnetic storm began January 11, 1955, reached Kp 5 and lasted 6 hours, with a daily Ap as high as 16; at that Kp the aurora may be seen from about 60 degrees geomagnetic latitude.
The Kp through the storm
Began Jan 11, 21:00 UTC, peaked in the block from Jan 11, 21:00 UTC, ended Jan 12, 03:00 UTC.
The storm
- Peak Kp
- 5 (5.00)
- NOAA level
- G1 Minor
- Duration
- 6 hours
- Highest daily Ap
- 16
- Highest 3-hour ap
- 48
- Rank since 1932
- 3,115 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 60 degrees geomagnetic latitude: 52°N in the central US, 51°N in the eastern US, 54°N in the western US and 61°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 |
|---|---|---|
| January 11, 1955 | 16 | 5 |
| January 12, 1955 | 9 | 5 |
More
The storm after, Jan 17Every storm of 1955The 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 2026-09-25.