The mysteries of black and anti-black auroras
|SPEAKER:||Prof. Mike Kosch, South African National Space Agency, Hermanus|
|VENUE:||iThemba LABS, Auditorium|
Normal colourful auroras are caused by high energy electrons bombarding the atmosphere and so energising the oxygen atoms and nitrogen molecules to release photons, which we see as auroras. However, there also exist the black auroras where the brightness is reduced relative to background intensity. Black auroras are regions of the sky where auroras are expected but do not appear. They are observed either as small patches or black rings that drift, mainly eastward; or as thin black arcs with specific motions and vortices. Black auroras, whilst commonly observed at high latitudes, remain a mysterious part of our space environment whose mechanism is still unknown. Recently, the anti-black aurora were also discovered. We explore what is known about black auroras and take a brief look at the “adventures” of researchers trying to understand them.