Space Education
Historical Space Weather Database
A searchable record of history's most significant solar flares and geomagnetic storms — from the Carrington Event of 1859 to the Gannon Storm of 2024.
Each entry gives the date, the strength of the event on the scales scientists use today, and what it did on Earth: telegraph fires in 1859, the Québec power grid collapse in 1989, satellites lost in 2003, aurora seen as far south as Mexico in 2024. Open any event for its full story and the original source. Older events are rated from surviving records such as magnetometer traces, ice cores and aurora sightings, so their strength is an expert estimate rather than a modern measurement.
34 events
How these events are measured
The archive rates each event with the same scales used for today's live Kp index and solar flare tracker, so a historical storm can be compared directly with current conditions.
- Kp index (0–9)
- A three-hourly measure of how disturbed Earth's magnetic field is, combined from magnetometers around the world. Kp 5 is a minor storm; Kp 9 is the top of the scale and was reached in 1989, 2003 and 2024.
- NOAA G-scale (G1–G5)
- NOAA's storm scale, tied to Kp: G1 is Kp 5 and G5 is Kp 9. G5 storms can cause widespread voltage control problems on power grids and push aurora to mid-latitudes.
- Solar flare classes (A, B, C, M, X)
- Flares are graded by peak X-ray brightness measured by satellites. Each letter is ten times stronger than the one before; X10 is ten times an X1. The biggest recorded flare, in November 2003, saturated the sensors and was later estimated near X28 to X45.
- Dst index
- A measure of the ring current around Earth, in nanotesla. The more negative, the stronger the storm. The 1989 storm reached about −589 nT; estimates for the 1859 Carrington Event range from roughly −850 to −1,750 nT.
Four eras of space weather history
Before 1900: telegraphs and eyewitness aurora
Records come from observatory magnetometers, ships' logs and newspaper aurora reports. The 1859 Carrington Event is the benchmark, the first flare ever seen, followed within a day by a storm that sparked telegraph lines.
1900–1957: radio and the early power grid
The 1921 New York Railroad storm disrupted telegraphs and signalling across North America and Europe. In 1942 British radar operators discovered that the Sun emits radio bursts strong enough to jam military equipment.
1957–1990: the space age
Satellites began measuring the Sun directly. The August 1972 storm fell between Apollo missions and could have been dangerous to astronauts. In March 1989 a storm collapsed Québec's grid in about 90 seconds.
1990 to today: a technology-dependent world
Modern storms are judged by their effect on satellites, GPS, aviation and grids. The 2003 Halloween Storms damaged spacecraft and rerouted flights; the May 2024 Gannon Storm was the strongest in two decades and showed aurora to millions.
For a year-by-year view, see the space weather timeline or the biggest solar storms in history.
Frequently asked questions
What was the strongest solar storm in recorded history?
The Carrington Event of September 1859 is generally considered the strongest geomagnetic storm on record, with aurora seen near the tropics. Tree-ring evidence points to even larger solar particle events in 774–775 AD, before modern records.
How often do extreme storms happen?
G5 (Kp 9) storms happen a few times per 11-year solar cycle on average, and some cycles have none. Carrington-scale storms are far rarer; published estimates of the chance of one in any decade vary widely, from a few percent to around ten percent.
Could a Carrington-class storm happen again?
Yes. In July 2012 a comparable eruption crossed Earth's orbit about a week after Earth had passed that point. Grid operators and satellite companies now plan for such an event, using warnings from NOAA's Space Weather Prediction Center.
Where does this archive's information come from?
Each event page links its original source, such as NOAA, NASA, peer-reviewed papers or historical records. Strengths for events before the space age are expert reconstructions, not direct measurements.
Compare with today
See how current activity stacks up against these events on the geomagnetic storm page and the live space weather dashboard.