On the origin of striae in cometary dust tails

It has been argued by Sekanina that the so-called striae or pseudo-synchronic bands observed in the dust tails of several comets are a consequence of the sudden disruption of elongated or chainlike parent grains in the tail. The present paper offers a specific mechanism for this disruption process, that is, electrostatic disruption following sudden charging to high electrostatic potentials. Assuming the grains to be prolate spheroids, it is shown that they can attain potentials in the range -60 V to -300 V when subject to energetic electron beams (1-10 keV). The energy source for these electrons is the interaction of the solar wind with the cometary ionosphere producing currents and associated electrostatic double layers.