The Largest Magnetic Storm on Record

The 'Carrington Event' of August 27th to September 7th, 1859
Recorded at Greenwich Observatory, London

Declination, or compass direction, (D) is the lower trace on each image and the horizontal force (H) is the upper trace. Universal Time is the time recorded here (astronomical) plus 12 hours and measured D precedes H by approximately 12 hours. For reference the marked ‘solar flare effect’, beginning at 23:15 recorded time on August 31st, is at 11:15 Universal Time on September 1st. It has been measured as 110 nT in H and 0.283 degrees in D.

Please note that these timings are approximate and should not be regarded as definitive. Also note, the size and scale of each image is only approximately similar, day-to-day. Some data have also been lost, either due to ink and paper degradation, or because the variations were so large they were off-scale.

You can also download all 12 full-size images as a poster (file size 23MB).

This is one example of the historical data contained in the British Geological Survey geomagnetic archives. We are currently re-examining our data holdings of old magnetograms and yearbooks in the hope of allowing greater access to these records in the future.