Once simply a source of awe and wonder for the ancients, terrestrial aurorae are also indications of
the level of emissions from the sun – some intense enough to be dangerous to modern civilisation.
Professor Alan Aylward’s lecture ranged over historical and pre-historical perceptions of the aurora
borealis (and its southern cousin aurora australis), concluding that the surprising (to us) recorded
observations as far south as Babylonia were due to the precession of the magnetic pole over
millennia. Serious attempts to determine the science behind the spectacular phenomena began
following the Maunder minimum in the late 18th century, and the link to the sunspot cycle was well
More modern science showed that the solar wind that slides round and buffets the earth’s
magnetosphere was directly responsible for the phenomena, and computer simulation of the
associated field lines explained why the aurora appeared as a circle around the magnetic pole.
Prof Aylward told us that the colours of the aurora, though often green, could also result from
atomic oxygen (red) and nitrogen (purple). More recent observations had identified short-lived
phenomena such as “sprites” and “blue jets” which were associated with aurorae.
Aurorae could be seen on other planets – principally Jupiter, but also associated with exoplanets and
even brown dwarfs. Prof Aylward’s talk gave rise to a discussion and a number of questions.