On the hydromagnetic model of comets

Several consequences of Alfven's (1957) hydromagnetic model of comets are developed. It is shown that such a model not only accounts for the observed morphology and time variations of the fine structure in the plasma tail, but also leads, in a natural way, towards explanations of two of the central problems in cometary physics; namely, the short ionization time-scales of the cometary molecules, and the large velocities and accelerations observed far down the tail.