Discussion of letter by J. A. Van Allen, ‘Further remarks on the absence of a very extended magnetospheric tail’

Van Allen [1966] has formulated four ‘test questions’ that he has applied to the long-tail model of the magnetosphere. He concludes that the data indicated a magnetospheric tail shorter than about 0.1 AU. It is the purpose of this discussion to point out that two of these same test questions may also be applied to argue against the short-tail model: one test question is indefinite, and one test question is not a test of either model. Therefore, these test questions, in themselves, do not allow an unambiguous conclusion to be drawn regarding the length of the magnetospheric tail.