Photometric Observations of Subvisual Red Auroral Arcs at Middle Latitudes

Abstract

A photometer (Roach et aT. 1958) sensitive to the red oxygen emission at 6300 A has been in operation at Oamden, near Sydney (geomagnetic latitude 42�), since July 1958. In this period three bright aurorae have been seen in southern Australia; on July 8-9, September 4-5, and September 25-26. Following the first two the photometer detected a subvisual stable red arc the next night. On the night after the third aurora, observation was prevented by cloud.