The Anatomy of Twilight Phenomena

Abstract

A great many factors, themselves subject to strong fluctuations, combine to produce the wealth of twilight phenomena and their variations in space and time. As a result, an exceptionally diverse range of behavior can occur, but by the same token the twilight period becomes very difficult to analyze adequately. We have already shown that a rigorous analysis of twilight phenomena would require solving the equation of transfer, and that a solution still remains unattainable, or at least none has been achieved. But even at best we can expect to do nothing more than use computing machines to arrive at a limited set of solutions for special and highly idealized cases. This procedure would be of no avail as a basis for developing methods of solving the inverse problem —using twilight phenomena for studying the upper layers of the atmosphere. Thus the only course open to us has been to formulate an approximate theory for twilight with the roles of the various factors clearly expressed. We are faced with the need to explain the anatomy of the several twilight phenomena, that is, to learn what the most important relationships are between the character of the phenomena and the structure of the atmosphere.