This volume, which was first published in 1991, presents a comprehensive review of all aspects of the physics of the aurorae australis and borealis. The broad topics covered relate to the different sections of a conference held in Cambridge to celebrate the centenary of the birth of Professor Sydney Chapman, FRS, who can be considered the founder of the subject in its modern form. Contributions from an international group of experts in the field discuss the physical causes and effects of the aurorae, the nightly show of dancing lights in the atmosphere, at heights above 100 km. The book is aimed primarily at students and researchers in auroral physics, but will also be of interest to magnetospheric, ionospheric and atomospheric physicists.