Heart of the black auroras revealed by Cluster
Thursday, April 9, 2015 - 08:00
in Astronomy & Space
Most people have heard of auroras - more commonly known as the Northern and Southern Lights - but, except on rare occasions, such as the recent widespread apparition on 17 March, they are not usually visible outside the polar regions. Less familiar are phenomena known as black auroras, dark patches which often subdivide the glowing curtains of red and green light.