The solar-comet interactions

Abstract

The central theme of this review is the role of the plasma tails of comets as free natural probes of the solar wind. It was the behavior of the plasma tails of comets that provided the earliest indication of the continuous ouflow of corpuscular radiation from the sun, which we now call the solar wind. In this role comets have not been entirely superseded by the advent of artificial space probes since these, with few recent exceptions are confined to the regions close to the ecliptic plane. Long period comets, on the other hand approach the sun at all inclinations and a few of them get closer to it than any artficial probe has, or will, in the near future. So comets provide us information both of the global properties of the solar wind as well as its spatial and temporal variations. Following a brief summary of the origin and nature of the cometary nucleus a detailed account is given of the interaction of a comet approaching the sun with solar EM radiation and the solar wind since this is what is central to all observed cometary phenomena (outgassing, ionization, and the formation of dust and plasma tails. The review is concluded with some speculations on the expected contributions of forthcoming space missions to the furtherance of our understanding of the subject. © 2007 Springer-Verlag.