Further remarks on the absence of a very extended magnetospheric tail

Any worthy theory of the structure and length of the magnetospheric tail must be prepared to deal with questions of quantitative physical significance. That is to say, it must be subject to one or more observational tests which can, at least in principle, determine the presence or absence of the tail at specified points in space. Dessler and collaborators [ Dessler , 1964; Michel and Dessler , 1965; Dessler and Juday , 1965; Michel , 1965] have hypothesized that the magnetospheric tail of the earth extends to some 20 to 50 AU (astronomical units) (∼10 6 R E [earth radii]) in the antisolar direction. Dungey [1965] has contested this hypothesis on grounds of semiempirical implausibility.