Combining historical sunspot drawings, ground magnetograms, and worldwide auroral reports, this study reconstructs the geomagnetic superstorm of 1872 February 4 (named here the Chapman-Silverman storm). The likely driver was an eruption near disk center from a moderate but complex active region on February 3, giving a roughly 29-hour transit to Earth; magnetograms place a sudden commencement near 14:27 UT and bound the storm's minimum Dst at <= -834 nT. Overhead aurorae credibly reported near 19.9 degrees magnetic latitude (Jacobabad, Shanghai) and low-latitude auroral visibility from thirteen sites imply an intensity comparable to the 1859 Carrington and 1921 May storms, ranking 1872 among the three largest geomagnetic storms on record.
We review observations of solar activity, geomagnetic variation, and auroral visibility for the extreme geomagnetic storm on 1872 February 4. The extreme storm (referred to here as the Chapman-Silver…