Earth Planets Space, Vol. 59 (No. 11), pp. e49-e51, 2007E-LETTER
J. M. Vaquero1, R. M. Trigo2,3, and M. C. Gallego4
1Departamento de Física Aplicada, Escuela Politécnica, Universidad de Extremadura, Cáceres, Spain
2University of Lisbon, CGUL, IDL, Lisbon, Portugal
3Departamento de Enghenharias e Ciĕncias Naturais, Universidade Lusófona, Lisbon, Portugal
4Departamento de Física, Facultad de Ciencias, Universidad de Extremadura, Badajoz, Spain
(Received October 16, 2007; Revised November 15, 2007; Accepted November 16, 2007; Online published November 22, 2007)
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.
Key words: Sporadic aurora, low geomagnetic activity.