Abstract. While low-latitude auroral displays are normally considered to be a
manifestation of magnetic storms of considerable size, Silverman (2003, JGR,
108, A4) reported numerous “sporadic auroras” which appear locally at
relatively low magnetic latitude during times of just moderate magnetic
activity. Here, a case study is presented of an aurora near the geomagnetic
equator based on a report from the Philippine islands on 27 October 1856. An
analysis of this report shows it to be consistent with the known cases of
sporadic auroras, except for its appearance at considerably low magnetic latitude. The
record also suggests that an extremely low-latitude aurora is not always
accompanied by large magnetic storms. The description of its brief appearance
leads to a possible physical explanation based on an ephemeral magnetospheric
disturbance provoking this sporadic aurora.
Sporadic Aurora near Geomagnetic Equator: In the Philippines, on
27 October 1856
