Abstract
A wavy structure in the near tail of comet Halley was observed in Tonantzintla on 12 April 1986. Recent spacecraft encounters with comets have confirmed the Alfvén field line draping model of cometary tails. On the basis of this result, the author discusses the origin of the structure by considering an equilibrium which consists of a neutral current sheet with a non-vanishing amount of magnetic flux through it. The author proposes that the observed structure is a consequence of the onset of a collisionless tearing instability in the above mentioned plasma equilibrium. Such a magnetic reconnection process could be triggered by an interplanetary shock.
