Sporadic Aurora from Spain
Vaquero J.M., Trigo R.M., Gallego M.C.
Earth Planets Space, Vol 59, e40-e51
Some authors have shown recently that "sporadic auroras" have occurred at relatively low latitude when the geomagnetic activity is quiet or moderate. Here we present and analyze a case of "sporadic aurora" observed from Spain on the 29 December 1845 and compare its low geomagnetic activity with other three aurorae also observed in Spain in mid-19th century.