G3 (Strong) Geomagnetic Storm of September 9, 1992

Name: G3 (Strong) Geomagnetic Storm of September 9, 1992
Start: 1992-09-09T00:00:00.000Z
End: 1992-09-11T03:00:00.000Z
Location: Earth

September 9 to 11, 1992 · 51 hours

A G3 (strong) geomagnetic storm began September 9, 1992, reached Kp 7+ and lasted 51 hours, with a daily Ap as high as 88; at that Kp the aurora may be seen from about 48 degrees geomagnetic latitude.

The Kp through the storm

Began Sep 9, 00:00 UTC, peaked in the block from Sep 9, 09:00 UTC, ended Sep 11, 03:00 UTC.

From 00 UT the day before to the end of the day after. Blocks in the storm are colored by level; the rest are gray.

The storm

Peak Kp: 7+ (7.33)
NOAA level: G3 Strong
Duration: 51 hours
Highest daily Ap: 88
Highest 3-hour ap: 154
Rank since 1932: 291 of 4,139

How far south the aurora could have been seen

At Kp 7+ NOAA’s scales put the aurora’s reach at about 48 degrees geomagnetic latitude: 40°N in the central US, 39°N in the eastern US, 43°N in the western US and 49°N in northern Europe.

NOAA says a G3 storm’s aurora has been seen as low as Illinois and Oregon.

US cities within reach, the southernmost first

Baltimore, MD 48.5° geomag.
Indianapolis, IN 48.7° geomag.
Columbus, OH 49.0° geomag.
Lincoln, NE 49.1° geomag.
Philadelphia, PA 49.1° geomag.
Eugene, OR 49.4° geomag.
Pittsburgh, PA 49.6° geomag.
Omaha, NE 49.6° geomag.
Staten Island, NY 49.8° geomag.
Brooklyn, NY 49.8° geomag.

53 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.

Tonight’s aurora forecast

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
September 9, 1992	84	7+
September 10, 1992	88	7
September 11, 1992	33	6+

Flares before it

Peak (UTC)	Class	Region	Before the storm began
Sep 6, 18:46 UTC	X1.7	NOAA 7270	53 hours
Sep 6, 21:00 UTC	X1.3	NOAA 7270	51 hours
Sep 7, 06:34 UTC	M7.1	NOAA 7270	41 hours
Sep 7, 19:36 UTC	M5.7	NOAA 7270	28 hours
Sep 5, 11:29 UTC	M4.0	NOAA 7270	85 hours
Sep 6, 12:07 UTC	M4.0	NOAA 7270	60 hours

The strongest M and X class flares GOES recorded from four days before the storm began to its end, the window in which a coronal mass ejection launched with a flare usually arrives. A flare in this list is context, not proof of the cause: many storms come from coronal holes, and many flares launch nothing toward Earth.

The storm before, Sep 4 The storm after, Sep 17 Every storm of 1992 The strongest on record This day in weather history Tonight’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. Flares from NOAA NCEI’s GOES X-ray flare reports (1975 to 2017) and SWPC’s edited solar event lists, public domain; classes as NOAA recorded them at the time.