Low-latitude auroras: The great aurora of 4 February 1872

The aurora of 4 February 1872 was comparable to, and perhaps even greater than, that of 1/2 September 1859. In this paper we show that the aurora of 4 February 1872 was seen worldwide, and that in the Caribbean, Egypt, Southern Africa, the Indian Ocean, the Indian subcontinent, and China these observations extended as low as 20° magnetic latitude. Observations are also available in the north to as far as the vicinity of the north magnetic pole. This aurora is then comparable to, or greater than, in geographical extent, and in equatorward closeness, to that of 2 September 1859. Both must now be included as the only known members in the class of greatest auroras of the past few hundred years. For the 1859 aurora, however, there is no accepted observation at a lower magnetic latitude than about 20°. By contrast, several observations for the aurora of 4 February 1872 are reported at magnetic latitudes of the order of 10°, and one probable observation at an even lower magnetic latitude of about 3°. This paper presents a survey and discussion of these observations.