The Ion Tails of Comets

Abstract

Examination of the light emitted from the tails of comets shows that one component of the tail consists of ionised gas (plasma) originating from the comet’s atmosphere (or ‘coma’).  The tail plasma streams away from the comet in the direction radially away from the Sun, and appears to flow along magnetic field lines which are shaped like sharply-bent hair-pins draped over the comet’s nucleus.  Here we review some features of the environment of a comet which may lead to an understanding of this phenomenon.